Blog archive

Wed

18

Oct

2017

Football is...(#30)

Training one-touch play for promising goal scoring opportunities.

Wed

18

Oct

2017

Football is...(#29)

The core connects arms and legs - train it use it.

Mon

16

Oct

2017

Football is...(#28)

Skillful players have a good first touch.

Mon

16

Oct

2017

Latest research in football - week 41 - 2017

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Effects of Unloaded vs. Loaded Plyometrics on Speed and Power Performance of Elite Young Soccer Players
Reference: Front Physiol. 2017 Sep 26;8:742. doi: 10.3389/fphys.2017.00742. eCollection 2017.
Authors: Kobal R, Pereira LA, Zanetti V, Ramirez-Campillo R, Loturco I
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5623051/pdf/fphys-08-00742.pdf
Summary: The purpose of this study was to investigate the effects of loaded and unloaded plyometric training strategies on speed and power performance of elite young soccer players. Twenty-three under-17 male soccer players (age: 15.9 ± 1.2 years, height: 178.3 ± 8.1 cm, body-mass (BM): 68.1 ± 9.3 kg) from the same club took part in this study. The athletes were pair-matched in two training groups: loaded vertical and horizontal jumps using an haltere type handheld with a load of 8% of the athletes' body mass (LJ; n = 12) and unloaded vertical and horizontal plyometrics (UJ; n = 11). Sprinting speeds at 5-, 10-, and 20-m, mean propulsive power (MPP) relative to the players' BM in the jump squat exercise, and performance in the squat jump (SJ) and countermovement jump (CMJ) were assessed pre- and post-training period. During the experimental period, soccer players performed 12 plyometric training sessions across a 6-week preseason period. Magnitude based inferences and standardized differences were used for statistical analysis. A very likely increase in the vertical jumps was observed for the LJ group (99/01/00 and 98/02/00 for SJ and CMJ, respectively). In the UJ group a likely increase was observed for both vertical jumps (83/16/01 and 90/10/00, for SJ and CMJ, respectively). An almost certainly decrease in the sprinting velocities along the 20-m course were found in the LJ group (00/00/100 for all split distances tested). Meanwhile, in the UJ likely to very likely decreases were observed for all sprinting velocities tested (03/18/79, 01/13/86, and 00/04/96, for velocities in 5-, 10-, and 20-m, respectively). No meaningful differences were observed for the MPP in either training group (11/85/04 and 37/55/08 for LJ and UJ, respectively). In summary, under-17 professional soccer players increased jumping ability after a 6-week preseason training program, using loaded or unloaded jumps. Despite these positive adaptations, both plyometric strategies failed to produce worthwhile improvements in maximal speed and power performances, which is possible related to the interference of concurrent training effects. New training strategies should be developed to ensure adequate balance between power and endurance loads throughout short (and high-volume) soccer preseasons.


#2 Soccer-based promotion of voluntary medical male circumcision: A mixed-methods feasibility study with secondary students in Uganda
Reference: PLoS One. 2017 Oct 9;12(10):e0185929. doi: 10.1371/journal.pone.0185929. eCollection 2017.
Authors: Miiro G, DeCelles J, Rutakumwa R, Nakiyingi-Miiro J, Muzira P, Ssembajjwe W, Musoke S, Gibson LJ, Hershow RB, Francis S, Torondel B, Ross DA, Weiss HA
Download link: http://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0185929&type=printable
Summary: The Ugandan government is committed to scaling-up proven HIV prevention strategies including safe male circumcision, and innovative strategies are needed to increase circumcision uptake. The aim of this study was to assess the acceptability and feasibility of implementing a soccer-based intervention ("Make The Cut") among schoolboys in a peri-urban district of Uganda. The intervention was led by trained, recently circumcised "coaches" who facilitated a 60-minute session delivered in schools, including an interactive penalty shoot-out game using metaphors for HIV prevention, sharing of the coaches' circumcision story, group discussion and ongoing engagement from the coach to facilitate linkage to male circumcision. The study took place in four secondary schools in Entebbe sub-district, Uganda. Acceptability of safe male circumcision was assessed through a cross-sectional quantitative survey. The feasibility of implementing the intervention was assessed by piloting the intervention in one school, modifying it, and implementing the modified version in a second school. Perceptions of the intervention were assessed with in-depth interviews with participants. Of the 210 boys in the cross-sectional survey, 59% reported being circumcised. Findings showed high levels of knowledge and generally favourable perceptions of circumcision. The initial implementation of Make The Cut resulted in 6/58 uncircumcised boys (10.3%) becoming circumcised. Changes made included increasing engagement with parents and improved liaison with schools regarding the timing of the intervention. Following this, uptake improved to 18/69 (26.1%) in the second school. In-depth interviews highlighted the important role of family and peer support and the coach in facilitating the decision to circumcise. This study showed that the modified Make The Cut intervention may be effective to increase uptake of safe male circumcision in this population. However, the intervention is time-intensive, and further work is needed to assess the cost-effectiveness of the intervention conducted at scale.


#3 The Effects of Foam Rolling as a Recovery Tool in Professional Soccer Players
Reference: J Strength Cond Res. 2017 Oct 7. doi: 10.1519/JSC.0000000000002277. [Epub ahead of print]
Authors: Rey E, Padron-Cabo A, Costa PB, Barcala-Furelos R
Summary: Foam rolling (FR) is a common strategy used after training and competition by players. However, no previous studies have assessed the effectiveness of FR as recovery tool in sports populations. The aim of this study was to examine the effectiveness of FR (20 minutes of foam rolling exercises on quadriceps, hamstrings, adductors, gluteals, and gastrocnemius) and passive recovery (20 minutes sit on a bench) interventions performed immediately after a training session on Total Quality Recovery (TQR), perceived muscle soreness, jump performance, agility, sprint, and flexibility 24 hours after the training. During 2 experimental sessions, 18 professional soccer players (age 26.6 ± 3.3 years; height: 180.2 ± 4.5 cm; body mass: 75.8 ± 4.7 kg) participated in a randomized fully controlled trial design. The first session was designed to collect the pre-test values of each variable. After baseline measurements, the players performed a standardized soccer training. At the end of training unit, all the players were randomly assigned to the FR recovery group and the passive recovery group. A second experimental session was carried out to obtain the posttest values. Results from the between-group analyses showed that FR had a large effect on the recovery in agility (Effect Sizes [ES]= 1.06), TQR (ES= 1.08), and perceived muscle soreness (ES= 1.02) in comparison to passive recovery group at 24 h post-training. Thus, it is recommended soccer coaches and physical trainers working with high-level players use a structured recovery session lasting from 15 to 20 min based on FR exercises that could be implemented at the end of a training session to enhance recovery between training loads.


#4 Injury prevention in male youth soccer: Current practices and perceptions of practitioners working at elite English academies
Reference: J Sports Sci. 2017 Oct 11:1-9. doi: 10.1080/02640414.2017.1389515. [Epub ahead of print]
Authors: Read PJ, Jimenez P, Oliver JL, Lloyd RS
Summary: Forty-one practitioners inclusive of physiotherapists, sports scientists and strength and conditioning coaches from the academies of elite soccer clubs in the United Kingdom completed an on-line questionnaire which examined their: (1) background information; (2) perceptions of injury occurrence and risk factors; (3) screening and return to play; and (4) approach to designing and delivering injury prevention programmes with a response rate of 55% (41/75). Contact injuries were the most common mechanism reported and players between 13-16 years of age were perceived to be at the greatest risk. Pertinent risk factors included: reduced lower limb and eccentric hamstring strength, proprioception, muscle imbalances, and under developed foundational movement skills. Joint range of motion, jump tests, the functional movement screen, overhead and single leg squats were the most utilised screening methods. Training modalities rated in order of importance included: resistance training, flexibility development, agility, plyometrics and balance training. Training frequency was most commonly once or twice per week, during warm-ups, independent sessions or a combination of both. Injury prevention strategies in this cohort appear to be logical; however, the classification of injury occurrence and application of screening tools to identify "at risk" players do not align with existing research. The frequency and type of training used may also be insufficient to elicit an appropriate stimulus to address pertinent risk factors based on current recommendations.


#5 The physical response to a simulated period of soccer-specific fixture congestion
Reference: J Strength Cond Res. 2017 Oct 10. doi: 10.1519/JSC.0000000000002257. [Epub ahead of print]
Authors: Page RM, Marrin K, Brogden CM, Greig M
Summary: The aim of this study was to assess the physiological, perceptual, and mechanical measures associated with the completion of a simulated period of short-term soccer-specific fixture congestion. Ten male semi-professional soccer players completed three trials of a treadmill-based match simulation, with 48 hours intervening each trial. A repeated measures general linear model identified significantly (P= 0.02) lower knee flexor peak torque (PT) recorded at 300 degs[BULLET OPERATOR]s in the second (141.27 ± 28.51 Nm) and third trials (139.12 ± 26.23 Nm) when compared to the first (154.17 ± 35.25 Nm). Similarly, muscle soreness (MS) and PT data recorded at 60 degs[BULLET OPERATOR]s were significantly (P< 0.05) different in the third trial (MS= 42 ± 25 a.u; PT60= 131.10 ± 35.38 Nm) when compared to the first (MS= 29 ± 29 a.u; PT60= 145.61 ± 42.86 Nm). Significant (P= 0.003) differences were also observed for mean Bicep Femoris electromyography (EMGmean) between the third trial (T0-15= 126.36 ± 15.57 µV; T75-90= 52.18 ± 17.19 µV) and corresponding time points in the first trial (T0-15= 98.20 ± 23.49 µV; T75-90= 99.97 ± 39.81 µV). Cumulative increases in perceived exertion, heart rate, oxygen consumption, blood lactate concentrations, EMGmean, and PlayerLoad were recorded across each trial. MS and PT were also significantly different post-trial. There were however no significant main effects or interactions for the salivary Immunoglobulin A, and the medial-lateral PlayerLoad metrics. These data suggest a biomechanical and muscular emphasis with residual fatigue, with implications for injury risk and the development of recovery strategies.


#6 Steroid hormones and psychological responses to soccer matches: Insights from a systematic review and meta-analysis
Reference: PLoS One. 2017 Oct 12;12(10):e0186100. doi: 10.1371/journal.pone.0186100. eCollection 2017.
Authors: Slimani M, Baker JS, Cheour F, Taylor L, Bragazzi NL
Download link: http://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0186100&type=printable
Summary: The present systematic review and meta-analysis aimed to assess the perturbations in hormonal and psychological homeostasis in response to soccer match-play. These perturbations were explored according to match outcome (i.e., win versus loss), gender, type of contest (i.e., competitive versus non-competitive fixtures) and competitive level (i.e., novice versus high-level). The review was conducted according to the Population/Intervention or Exposure/Comparison/Outcome(s) (PICO) criteria and the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines. Match outcome, type of contest and competitive levels were moderator variables in the examined steroid hormones responses to a soccer match-play. Different testosterone responses were seen between match winners (increase) and losers (decrease) when compared to pre-game or baseline values (p <0.05), whilst no changes could be detected for cortisol relative to match outcome in female soccer players. Males (Δ% = 6.26; ES = 0.28) demonstrated a marginally lower increase in testosterone levels when compared to females (Δ% = 49.16; ES = 1.00), though not statistically significant. Females (Δ% = 162.7; ES = 0.98) did not demonstrate elevated cortisol match response compared to males (Δ% = 34.60; ES = 1.20). Male novice soccer match-play increased cortisol levels compared to high-level soccer match-play (Q = 18.08, p<0.001). Competitive soccer matches increased cortisol levels compared to non-competitive fixtures (i.e., collegiate tournament). Additionally, competitive levels moderate the relationship between a soccer match and testosterone levels (p <0.001), regardless of gender differences. From the presented systematic review and meta-analysis it appears (1) cortisol changes are associated with cognitive anxiety in starter female soccer players, while (2) testosterone changes are associated with changes in mood state in females and social connectedness in male soccer players. This apparent psycho-physiological relationship may proffer the opportunity for targeted intervention(s) by practitioners to favorably influence performance and/or recovery agendas. Further mechanistic and/or applied evidence is required in this regard in addition to further data sets from females.


#7 Effects of Plyometric Training on Components of Physical Fitness in Prepuberal Male Soccer Athletes: The Role of Surface Instability
Reference: J Strength Cond Res. 2017 Oct 10. doi: 10.1519/JSC.0000000000002262. [Epub ahead of print]
Authors: Negra Y, Chaabene H, Sammoud S, Bouguezzi R, Mkaouer B, Hachana Y, Granacher U
Summary: Previous studies contrasted the effects of plyometric training (PT) conducted on stable vs. unstable surfaces on components of physical fitness in child and adolescent soccer players. Depending on the training modality (stable vs. unstable), specific performance improvements were found for jump (stable PT) and balance performances (unstable PT). In an attempt to combine the effects of both training modalities, this study examined the effects of PT on stable surfaces compared with combined PT on stable and unstable surfaces on components of physical fitness in prepuberal male soccer athletes. Thirty-three boys were randomly assigned to either a PT on stable surfaces (PTS; n = 17; age = 12.1 ± 0.5 years; height = 151.6 ± 5.7 cm; body mass = 39.2 ± 6.5 kg; and maturity offset = -2.3 ± 0.5 years) or a combined PT on stable and unstable surfaces (PTC; n = 16; age = 12.2 ± 0.6 years; height = 154.6 ± 8.1 cm; body mass = 38.7 ± 5.0 kg; and maturity offset = -2.2 ± 0.6 years). Both intervention groups conducted 4 soccer-specific training sessions per week combined with either 2 PTS or PTC sessions. Before and after 8 weeks of training, proxies of muscle power (e.g., countermovement jump [CMJ], standing long jump [SLJ]), muscle strength (e.g., reactive strength index [RSI]), speed (e.g., 20-m sprint test), agility (e.g., modified Illinois change of direction test [MICODT]), static balance (e.g., stable stork balance test [SSBT]), and dynamic balance (unstable stork balance test [USBT]) were tested. An analysis of covariance model was used to test between-group differences (PTS vs. PTC) at posttest using baseline outcomes as covariates. No significant between-group differences at posttest were observed for CMJ (p > 0.05, d = 0.41), SLJ (p > 0.05, d = 0.36), RSI (p > 0.05, d = 0.57), 20-m sprint test (p > 0.05, d = 0.06), MICODT (p > 0.05, d = 0.23), and SSBT (p > 0.05, d = 0.20). However, statistically significant between-group differences at posttest were noted for the USBT (p < 0.01, d = 1.49) in favor of the PTC group. For most physical fitness tests (except RSI), significant pre-to-post improvements were observed for both groups (p < 0.01, d = 0.55-3.96). Eight weeks of PTS or PTC resulted in similar performance improvements in components of physical fitness except for dynamic balance. From a performance-enhancing perspective, PTC is recommended for pediatric strength and conditioning coaches because it produced comparable training effects as PTS on proxies of muscle power, muscle strength, speed, agility, static balance, and additional effects on dynamic balance.


American Football
#1 Heart Rate Variability and Training Load Among National Collegiate Athletic Association Division 1 College Football Players Throughout Spring Camp
Reference: J Strength Cond Res. 2017 Oct 10. doi: 10.1519/JSC.0000000000002241. [Epub ahead of print]
Authors: Flatt AA, Esco MR, Allen JR, Robinson JB, Earley RL, Fedewa MV, Bragg A, Keith CM, Wingo JE
Summary: The purpose of this study was to determine whether recovery of cardiac-autonomic activity to baseline occurs between consecutive-day training sessions among positional groups of a collegiate football team during Spring camp. A secondary aim was to evaluate relationships between chronic (i.e., 4-week) heart rate variability (HRV) and training load parameters. Baseline HRV (lnRMSSD_BL) was compared with HRV after ∼20 hours of recovery before next-day training (lnRMSSDpost20) among positional groups composed of SKILL (n = 11), MID-SKILL (n = 9), and LINEMEN (n = 5) with a linear mixed model and effect sizes (ES). Pearson and partial correlations were used to quantify relationships between chronic mean and coefficient of variation (CV) of lnRMSSD (lnRMSSD_chronic and lnRMSSDcv, respectively) with the mean and CV of PlayerLoad (PL_chronic and PL_cv, respectively). A position × time interaction was observed for lnRMSSD (p = 0.01). lnRMSSD_BL was higher than lnRMSSDpost20 for LINEMEN (p < 0.01; ES = large), whereas differences for SKILL and MID-SKILL were not statistically different (p > 0.05). Players with greater body mass experienced larger reductions in lnRMSSD (r = -0.62, p < 0.01). Longitudinally, lnRMSSDcv was significantly related to body mass (r = 0.48) and PL_chronic (r = -0.60). After adjusting for body mass, lnRMSSDcv and PL_chronic remained significantly related (r = -0.43). The ∼20-hour recovery time between training sessions on consecutive days may not be adequate for restoration of cardiac-parasympathetic activity to baseline among LINEMEN. Players with a lower chronic training load throughout camp experienced greater fluctuation in lnRMSSD (i.e., lnRMSSDcv) and vice versa. Thus, a capacity for greater chronic workloads may be protective against perturbations in cardiac-autonomic homeostasis among American college football players.


#2 Longitudinal Changes in Body Composition throughout Successive Seasonal Phases among Canadian University Football Players
Reference: J Strength Cond Res. 2017 Oct 7. doi: 10.1519/JSC.0000000000002011. [Epub ahead of print]
Authors: Kim J, Delisle-Houde P, Reid RE, Andersen RE.
Summary: The purpose of this study was to assess changes in body composition during seasonal phases of the training year among Canadian Inter-University Sport (CIS) football players. Forty university football players were assessed for anthropometry, total body composition, regional body composition and central adiposity over a 7-month period including the summer-off-season and the in-season. Baseline testing occurred in April, prior to the summer-off-season, and follow-ups were completed prior to training camp, at the beginning of August, and following the in-season, at the beginning of November. Linemen had the greatest tissue percent fat (25.98 ± 6.56%) at baseline, significantly (p < 0.01) greater than big skill (18.69 ± 3.97%) and followed by skill (14.35 ± 3.39%) who were significantly (p < 0.01) leaner than both other groups. Skill players significantly increased fat mass (0.98 ± 0.30 kg, p < 0.05) and waist-to-hip ratio (WHR; 0.02 ± 0.01, p ≤ 0.05) during the in-season, and linemen increased visceral fat mass from April to November (0.20 ± 0.06 kg, p ≤ 0.01). All players significantly (-1.26 ± 0.30 kg, p = 0.001) decreased lean mass during the in-season. All groups significantly increased bone mineral content during the summer-off-season (p < 0.05). There was also a significant time × summer training location interaction (p < 0.05) for fat mass with athletes who remained on campus during summer months gaining the least amount of adiposity. Body composition and central adiposity appear to change differentially among positional groups across the annual training season.


#3 Age at First Exposure to Repetitive Head Impacts Is Associated with Smaller Thalamic Volumes in Former Professional American Football Players
Reference: J Neurotrauma. 2017 Oct 7. doi: 10.1089/neu.2017.5145. [Epub ahead of print]
Authors: Schultz V, Stern RA, Tripodis Y, Stamm JM, Wrobel P, Lepage C, Weir I, Guenette JP, Chua A, Alosco ML, Baugh CM, Fritts NG, Martin B, Chaisson C, Coleman MJ, Lin AP, Pasternak O, Shenton ME, Koerte IK
Summary: Thalamic atrophy has been associated with exposure to repetitive head impacts (RHI) in professional fighters. The aim of this study is to investigate whether or not age at first exposure (AFE) to RHI is associated with thalamic volume in symptomatic former National Football League (NFL) players at risk for chronic traumatic encephalopathy (CTE). Eighty-six symptomatic former NFL players (mean age=54.9±7.9 years) were included. T1-weighted data were acquired on a 3T MRI and thalamic volumes were derived using FreeSurfer. Mood and behavior, psychomotor speed, and visual and verbal memory were assessed. The association between thalamic volume and AFE to playing football, and to number of years playing were calculated. Decreased thalamic volume was associated with more years of play (left: p=0.03; right: p=0.03). Younger AFE was associated with decreased right thalamic volume (p=0.014). This association remained significant after adjusting for total years of play. Decreased left thalamic volume was associated with worse visual memory (p=0.014), whereas increased right thalamic volume was associated with fewer mood and behavior symptoms (p=0.003). In our sample of symptomatic former NFL players at risk for CTE, total years of play, and AFE were associated with decreased thalamic volume. The effect of AFE on right thalamic volume was almost twice as strong as the effect of total years of play. Our findings confirm previous reports of an association between thalamic volume and exposure to RHI. They further suggest that younger AFE may result in smaller thalamic volume later in life.


#4 Anthropometrics and maturity status: A preliminary study of youth football head impact biomechanics
Reference: Int J Psychophysiol. 2017 Oct 3. pii: S0167-8760(17)30580-9. doi: 10.1016/j.ijpsycho.2017.09.022. [Epub ahead of print]
Authors: Yeargin SW, Kingsley P, Mensch JM, Mihalik JP, Monsma EV
Summary: There is a paucity of head impact biomechanics research focusing on youth athletes. Little is known about how youth subconcussive head impact tolerances are related to physical size and maturation. The objective was to examine the effects of age, anthropometric and maturational status variability on head impact biomechanics. Thirty-four male recreational youth football players, 8 to 13yrs participated in this study. Categorized by CDC standards, independent variables were: age, height, mass, BMI, and estimated peak height velocity (PHV). Participants wore a designated head impact sensor (xPatch) on their mastoid process during practices and games. Main outcome measures were Linear acceleration (g) and rotational acceleration (rad/s2). Boys in the older age category had a greater linear (F=17.72; P<0.001) and rotational acceleration (F=10.74; P<0.001) than those in the younger category. Post-PHV boys had higher linear (F=9.09, P=0.002) and rotational (F=5.57, P=0.018) accelerations than those who were pre-PHV. Rotational, but not linear acceleration differed by height category with lowest impacts found for the tallest category, whereas both linear and rotational accelerations by mass differences favored average and heavy categories. BMI overweight boys, had the greatest linear (F=5.25; P=0.011) and rotational acceleration (F=4.13; P=0.260) means. Post-PHV boys who were older, taller and had longer legs, but who were not heavier, had higher impacts perhaps due to the type of impacts sustained. Taller boys' heads are above their peers possibly encouraging hits in the torso region resulting in lower impact accelerations. Obese boys did not have sequential results compared to boys in the other BMI categories probably due to league rules, player position, and lack of momentum produced.

Mon

16

Oct

2017

Football is...(#27)

SSG = Technical + Tactical + Physical Training

Fri

13

Oct

2017

Football is...(#26)

Numerical (dis)advantages can be crucial.

Thu

12

Oct

2017

Football is...(#25)

Testing players intermittent running capacity - a suggestion.

Wed

11

Oct

2017

Latest research in football - week 40 - 2017

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Professional football players at risk for non-acute groin injuries during the first half of the season: A prospective cohort study in The Netherlands
Reference: J Back Musculoskelet Rehabil. 2017 Sep 15. doi: 10.3233/BMR-150427. [Epub ahead of print]
Authors: Gouttebarge V, Veenstra E, Goedegebuure S, Frings-Dresen M, Kuijer P
Summary: The purpose was to study the incidence, diagnostics, treatment, anatomical region and return to play of non-acute groin injuries among professional footballers in the Netherlands. Medical staff members of all Dutch professional football clubs, recording prospectively injury occurrence of all professional footballers in their clubs, were asked to fill in an injury form about time-loss (⩾ 8 days) non-acute groin injury over the 2012-2013 season. A cohort of 410 players from 12 professional football clubs were included (response rate = 44%). The season incidence of non-acute groin injuries was nearly 7% (29 non-acute groin injuries). In 82% of all cases, the player suffered from non-acute groin injury in the first half of the season. The average time to return to play was 35 days, ranging from 8 to 84 days. The adductors were the most affected anatomical regions (82%), with the most frequent diagnosis being overuse of the adductors (36%), followed by adductor tendinopathy (18%). In addition to medical history and physical examination, ultrasound (50%) and MRI (32%) were the diagnostic methods most frequently mentioned. As well as physical therapy, treatment consisted mostly of manual therapy (96%) and dry needling (61%). A professional club with a squad of 25 players can expect on average two non-acute groin injuries per season with an average time-loss of 35 days. Players are more at risk in the first half of the season. In Dutch professional football, ultrasound is commonly used to diagnose non-acute groin injury, while manual therapy is the most commonly applied treatment.


#2 Osteitis pubis in professional football players: MRI findings and correlation with clinical outcome
Reference: Eur J Radiol. 2017 Sep;94:46-52. doi: 10.1016/j.ejrad.2017.07.009. Epub 2017 Jul 19.
Authors: Gaudino F, Spira D, Bangert Y, Ott H, Beomonte Zobel B, Kauczor HU, Weber MA
Summary: Osteitis pubis (OP), a common pathology in elite athletes, is an aseptic inflammatory process of the pubic symphysis bone, and may involve surrounding soft tissues, tendons and muscles. OP is typically characterized by (often recurring) groin pain and is an important cause of time-off from sports activity in athletes. Aim of this retrospective study was to analyze magnetic resonance imaging (MRI) findings in professional football players with clinical diagnosis of OP and to correlate MRI findings with clinical outcome. All professional football players (23 males, 1 female; mean age: 21±3.7years; range: 16-30 years) with groin pain and clinical diagnosis of OP, who underwent pelvic MRI in our institution were retrospectively analyzed. The MR images were analyzed regarding the presence of bone marrow edema and its extension, whether fluid in the symphysis pubis or periarticular soft tissue edema with a rim-like periosteal distribution or edema in the muscles located around the symphyseal joint were present, whether degenerative changes of the symphysis pubis and of signs of symphyseal instability were encountered. A quantitative measurement of the signal intensity in bone marrow edema on 3T STIR sequences was performed, normalizing these values to the mean signal intensity values in the ipsilateral iliopsoas muscle. All patients were classified according to a 3-point grading scale. For each patient, both the symptoms 18 months after the initial MRI examination, the duration of time off from playing football and the kind of treatment applied were evaluated. Among all professional athletes, in 20/24 (83.3%) MRI showed signs of OP with bone marrow edema at the pubic bone. 12 of these patients showed complete clinical recovery without any symptoms after 18 months, while in 8 patients partial recovery with persistence of groin pain during higher sports activity was observed. Patients with edema in periarticular soft tissues or in the muscles around the symphyseal joint on MRI at the beginning of symptoms presented significantly more often with a partial recovery after returning to high sports activity (p=0.042 and p=0.036, respectively). A partial recovery was also significantly associated with higher normalized mean signal intensity values in bone marrow edema on STIR sequences at the beginning of symptoms (mean=4.77±1.63 in the group with partial recovery vs. mean=2.86±0.45 in the group with complete recovery; p=0.0019). No significant association was noticed between MRI findings and time of abstinence from high sports activity, as well as between the 3-point grading scale and the time off from high sport activity and recovery at 18 months. Edema in periarticular soft tissues, edema with extension to the muscles located around the symphyseal joint, as well as higher normalized signal intensity values in bone marrow edema on STIR sequences in the pubic bones at the beginning of groin pain are the most reliable MRI findings of a poor clinical long-term outcome of OP in professional football players and should be regarded as negative prognostic factors.


#3 Applying graphs and complex networks to football metric interpretation
Reference: Hum Mov Sci. 2017 Sep 20. pii: S0167-9457(17)30628-0. doi: 10.1016/j.humov.2017.08.022. [Epub ahead of print]
Authors: Arriaza-Ardiles E, Martin-Gonzalez JM, Zuniga MD, Sanchez-Flores J, de Saa Y, Garcia-Manso JM
Summary: This work presents a methodology for analysing the interactions between players in a football team, from the point of view of graph theory and complex networks. We model the complex network of passing interactions between players of a same team in 32 official matches of the Liga de Fútbol Profesional (Spain), using a passing/reception graph. This methodology allows us to understand the play structure of the team, by analysing the offensive phases of game-play. We utilise two different strategies for characterising the contribution of the players to the team: the clustering coefficient, and centrality metrics (closeness and betweenness). We show the application of this methodology by analyzing the performance of a professional Spanish team according to these metrics and the distribution of passing/reception in the field. Keeping in mind the dynamic nature of collective sports, in the future we will incorporate metrics which allows us to analyse the performance of the team also according to the circumstances of game-play and to different contextual variables such as, the utilisation of the field space, the time, and the ball, according to specific tactical situations.


#4 Mental Fatigue and Spatial References Impair Soccer Players' Physical and Tactical Performances
Reference: Front Psychol. 2017 Sep 21;8:1645. doi: 10.3389/fpsyg.2017.01645. eCollection 2017.
Authors: Coutinho D, Gonçalves B, Travassos B, Wong DP, Coutts AJ, Sampaio JE
Summary: This study examined the effects of mental fatigue and additional corridor and pitch sector lines on players' physical and tactical performances during soccer small-sided games. Twelve youth players performed four Gk+6vs6+Gk small-sided games. Prior to the game, one team performed a motor coordination task to induce mental fatigue, while the other one performed a control task. A repeated measures design allowed to compare players' performances across four conditions: (a) with mental fatigue against opponents without mental fatigue in a normal pitch (MEN), (b) with mental fatigue on a pitch with additional reference lines (#MEN); (c) without mental fatigue against mentally fatigued opponents on a normal pitch (CTR); and (d) without mental fatigue on a pitch with reference lines (#CTR). Player's physical performance was assessed by the distance covered per minute and the number of accelerations and decelerations (0.5-3.0 m/s2; > -3.0 m/s2). Positional data was used to determine individual (spatial exploration index, time synchronized in longitudinal and lateral directions) and team-related variables (length, width, speed of dispersion and contraction). Unclear effects were found for the physical activity measures in most of the conditions. There was a small decrease in time spent laterally synchronized and a moderate decrease in the contraction speed when MEN compared to the CTR. Also, there was a small decrease in the time spent longitudinally synchronized during the #MEN condition compared to MEN. The results showed that mental fatigue affects the ability to use environmental information and players' positioning, while the additional reference lines may have enhanced the use of less relevant information to guide their actions during the #MEN condition. Overall, coaches could manipulate the mental fatigue and reference lines to induce variability and adaptation in young soccer players' behavior.


#5 Exercise physiology and nutritional perspectives of elite soccer refereeing
Reference: Scand J Med Sci Sports. 2017 Oct 5. doi: 10.1111/sms.12989. [Epub ahead of print]
Authors: Schenk K, Bizzini M, Gatterer H
Summary: Referees are an integral part of soccer and their performance is fundamental for regular match flow, irrespective of the competition level or age classes. So far, scientific interest was mainly limited to aspects of exercise physiology and match performance of soccer referees, whereas recommendations for nutrition were adopted from active professional soccer. In contrast to elite soccer players most referees are non-professional and engaged in different occupations. Furthermore, elite referees and soccer players differ in regard to age, body composition, aerobic capacity and training load. Thus, referees' caloric needs and recommended daily carbohydrate intake may generally be lower compared to active soccer players, with higher intakes limited to periods of increased training load and match days or for referees engaged in physical demanding occupations. With respect to fluid intake, pre-match and in-match hydration strategies generally valid in sports are recommended also for referees to avoid cognitive and physical performance loss, especially when officiating in extreme climates and altitude. In contrast to elite soccer, professional assistance concerning nutrition and training is rarely available for national elite referees of most countries. Therefore, special attention on education about adequate nutrition and fluid intake, about the dietary prevention of deficiencies (iron in female referees, vitamin D irrespective of sex and age) and basic precautions for travels abroad is warranted. In conclusion, the simple adoption of nutritional considerations from active soccer for referees may not be appropriate. Recommendations should respect gender differences, population specific physical characteristics and demands just as well as individual characteristics and special needs.


#6 A rare case of localised pigmented villonodular synovitis in the knee of a 24-year-old female soccer player: diagnosis, management and summary of tenosynovial giant cell tumours
Reference: BMJ Case Rep. 2017 Oct 4;2017. pii: bcr-2017-219549. doi: 10.1136/bcr-2017-219549.
Authors: Falster C, Stockmann Poulsen S, Joergensen U
Summary: Localised pigmented villonodular synovitis (PVNS) of the knee is a rare diagnosis, with clinical signs and symptoms mimicking meniscal damage or other common knee injuries.We report the case of a 24-year-old female soccer player, seeking treatment after 7 months of persisting knee pain. Additionally, we present an overview of tenosynovial giant cell tumours.On examination, the patient was found to have tenderness in the medial joint space of the knee. MRI revealed a heterogeneous formation in the central part of the knee. The formation was completely enucleated arthroscopically, histological analyses confirmed the diagnosis of localised PVNS. The patient was subsequently free of symptoms with no signs of recurrence on MRI and had resumed soccer practice at the 1-year follow-up appointment.


#7 Genetic Variants and Hamstring Injury in Soccer: an Association and Validation Study
Reference: Med Sci Sports Exerc. 2017 Oct 2. doi: 10.1249/MSS.0000000000001434. [Epub ahead of print]
Authors: Larruskain J, Celorrio D, Barrio I, Odriozola A, Gil SM, Fernandez-Lopez JR, Nozal R, Ortuzar I, Lekue JA, Aznar JM.
Summary: The purpose was to investigate the association of candidate single nucleotide polymorphisms (SNPs) with non-contact hamstring muscle injuries in elite soccer players, and to create and validate a model to assess the risk of hamstring injury. 107 elite male outfield players were prospectively followed for 6 seasons. Players were genotyped for 37 SNPs previously investigated in relation to musculoskeletal injuries. The association of SNPs, previous injury, age, level of play, position and anthropometric data with 129 hamstring injuries (413 observations) was investigated in the discovery phase (2010-2015), and a multivariable Cox-frailty model was created using forward selection. The model's discriminative ability was tested in the validation phase (2015-2016, 31 injuries, 98 observations) using Harrell's C index. Five SNPs were found to be significantly associated with hamstring injury in a multivariable model, MMP3 (Matrix metalloproteinase-3) rs679620 (A vs. G, hazard ratio (HR)=2.06, 95% confidence interval (CI)=1.51-2.81), TNC (Tenascin-C) rs2104772 (A vs. T, HR=1.65, 95% CI=1.17-2.32), IL6 (Interleukin-6) rs1800795 (GG vs. GC+CC, HR=1.68, 95% CI=1.11-2.53), NOS3 (Nitric oxide synthase-3) rs1799983 (G vs. T, HR=1.35, 95% CI=1.01-1.79), and HIF1A (Hypoxia-inducible factor-1α) rs11549465 (CC vs. CT, HR=2.08, 95% CI=1.00-4.29). Age also entered the model (≥24 vs. <24 years, HR=2.10, 95% CI=1.29-3.42). The model showed acceptable discrimination in the discovery phase (C index=0.74), but not in the validation phase (C index=0.52). Genetic variants appear to be involved in the etiology of hamstring injuries, but were not found to have predictive value by themselves. Further research, increasing the number of genetic variants and including environmental factors in complex multifactorial risk models is necessary.


#8 Prevalence of femoroacetabular impingement morphology in asymptomatic youth soccer players: magnetic resonance imaging study with clinical correlation
Reference: Rev Bras Ortop. 2017 Jun 24;52(Suppl 1):14-20. doi: 10.1016/j.rboe.2017.06.005. eCollection 2017.
Authors: Yepez AK, Abreu M, Germani B, Galia CR
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5620002/pdf/main.pdf
Summary: The purpose was to determine the prevalence of femoroacetabular impingement morphology (FAIM), cam- or pincer-type, by magnetic resonance imaging (MRI) in asymptomatic adolescent soccer players, and to evaluate the possible correlation between alterations on MRI and clinical examination findings. A cross-sectional study was conducted to determine the prevalence of FAIM in asymptomatic youth soccer players aged 13-18 years. A total of 112 hips in 56 players (mean age 15.3 years) were evaluated by MRI. Images were examined by two musculoskeletal radiologists for signs of FAIM. Cam-type (impingement) deformity was diagnosed by alpha angle ≥55° or head-neck offset <7 mm. Pincer-type (impingement) deformity was diagnosed by center-edge angle (CEA) ≥35° or acetabular index ≤0°. Other MRI changes, characteristic of FAIM, were observed. Clinical examination was performed to determine the range of motion (ROM) of the hips. In addition, specific tests for anterolateral and posteroinferior impingement were performed. The prevalence of MRI findings consistent with FAIM among this young population was 84.8% (95/112). The alpha angle was ≥55° in 77.7% (87/112) of hips, while the CEA was altered in 10.7% (12/112) of hips. Qualitative MRI findings consistent with FAIM were highly prevalent, and included loss of sphericity of the femoral head (77%), osseous bump (44%), femoral neck edema (21%), and acetabular osteitis (9%). The anterior impingement test was positive in 15% of the hips evaluated. Youth soccer players have a high prevalence of FAIM as diagnosed by MRI. There is no correlation between physical examination findings and MRI evidence of FAIM in this population.


#9 In-Season High-Intensity Interval Training Improves Conditioning In High School Soccer Players
Reference: Int J Exerc Sci. 2017 Sep 1;10(5):713-720. eCollection 2017.
Authors: Howard N, Stavrianeas S
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5609662/pdf/ijes-10-05-713.pdf
Summary: Soccer is characterized by high aerobic demands interspersed with frequent bursts of anaerobic activity. High-intensity interval training (HIIT) is considered a viable alternative to traditional endurance conditioning and offers the additional time-saving benefits of anaerobic training. We hypothesized that HIIT will compare favorably to traditional (aerobic-based) soccer conditioning over the course of a high school soccer season. Junior varsity soccer players were split into control (CON, n=16) and experimental (HIIT, n=16) groups for the 10-week study. The HIIT group performed 4-6 "all-out" sprints lasting 30s each, with 4.5 minute recovery, 3 times a week. The CON group performed endurance running for the same duration. The groups did not differ in any other aspect of their training. Participants completed the Yo-Yo intermittent recovery test level 1 (IR1), a 40-yard dash, vertical jump, Illinois agility test, and a sit-and-reach test, in two different testing sessions (pre/post season). Both HIIT and CON groups exhibited significant increase in IR1 test performance with time (741.6±307.6m vs. 1067.6±356.8m, p<.001 and 733.2±318.8m vs. 1165.2±252.8m, p<0.001 respectively), with no difference between groups. The CON group demonstrated a significant difference in the 40-yard dash over time (5.48±0.36s vs. 5.21±0.16s, p<0.004). While there was a difference in vertical jump between the pre and post tests for the HIIT group (42.20±7.04cm vs. 47.87±750cm respectively, p<0.019), no such effect was observed in the CON group. In contrast, there were differences in the agility test only for the CON group over time (16.67±0.76s vs. 16.15±0.49s, p<0.001). There were no differences in the flexibility test between groups. Our results indicate that HIIT offers similar endurance improvements to more traditional soccer training.

#10 Maturation-related adaptations in running speed in response to sprint training in youth soccer players
Reference: J Sci Med Sport. 2017 Sep 21. pii: S1440-2440(17)31058-7. doi: 10.1016/j.jsams.2017.09.012. [Epub ahead of print]
Authors: Moran J, Parry DA, Lewis I, Collison J, Rumpf MC, Sandercock GRH
Summary: This study investigated the effects of a previously recommended dose of sprint training (ST) in young male soccer players of differing maturity status. Male soccer players from two professional academies were divided into Pre-PHV (Training: n=12; Control: n=13) and Mid-PHV (Training: n=7; Control=10) groups. The training groups completed 16 sprints of 20m with 90s recovery, once per week. Between-group effect sizes (ES) were substantially larger in Pre-PHV (10m [1.54, CI: 0.74-2.23]; 20m [1.49, CI: 0.75-2.23]; 5-10-5 [0.92, CI: 0.23-1.61]) than in Mid-PHV (10m [-0.00, CI: -0.81 to 0.81]; 20m [-0.12, CI: -0.93 to 0.69]; 5-10-5 [-0.41, CI: -1.22 to 0.41]). Within-group effects demonstrated a similar, though less accentuated, trend which revealed ST to be effective in both Pre-PHV (10m [0.44, CI: -0.24 to 1.12]; 20m [0.45, CI: -0.23 to 1.13]; 5-10-5 [0.69, CI: 0.00-1.38]) and Mid-PHV (10m [0.51, CI: -0.38 to 1.40]; 20m [0.33, CI: -0.56 to 1.21]; 5-10-5 [0.43, CI: -0.46 to 1.32]). ST, in the amount of 16 sprints over 20m with a 90s rest, may be more effective in Pre-PHV youths than in Mid-PHV youths.


American Football
#1 National Football League Skilled and Unskilled Positions Vary in Opportunity and Yield in Return to Play After an Anterior Cruciate Ligament Injury
Reference: Orthop J Sports Med. 2017 Sep 21;5(9):2325967117729334. doi: 10.1177/2325967117729334. eCollection 2017 Sep.
Authors: Yang J, Hodax JD, Machan JT, Secrist ES, Durand WM, Owens BD, Eltorai AEM, Dodson CC
Summary: Anterior cruciate ligament (ACL) injuries pose a significant risk to the careers of players in the National Football League (NFL). The relationships between draft round and position on return to play (RTP) among NFL players are not well understood, and the ability to return to preinjury performance levels remains unknown for most positions. The purpose was to test for differences in RTP rates and changes in performance after an ACL injury by position and draft round. We hypothesized that skilled positions would return at a lower rate compared to unskilled positions. We further hypothesized that early draft-round status would relate to a greater rate of RTP and that skilled positions and a lower draft round would correlate with decreased performance for players who return to sport. Utilizing a previously established database of publicly available information regarding ACL tears among NFL players, athletes with ACL tears occurring between the 2010 and 2013 seasons were identified. Generalized linear models and Kaplan-Meier time-to-event models were used to test the study hypotheses. The overall RTP rate was 61.7%, with skilled players and unskilled players returning at rates of 64.1% and 60.4%, respectively (P = .74). Early draft-round players and unskilled late draft-round players had greater rates of RTP compared to skilled late draft-round players and both unskilled and skilled undrafted free agents (UDFAs). Skilled early draft-round players constituted the only cohort that played significantly fewer games after an injury. Unskilled UDFAs constituted the only cohort to show a significant increase in the number of games started and ratio of games started to games played, starting more games in which they played, after an injury. Early draft-round and unskilled players were more likely to return compared to their later draft-round and skilled peers. Skilled early draft-round players, who displayed relatively high rates of RTP, constituted the only cohort to show a decline in performance. Unskilled UDFAs, who exhibited relatively low rates of RTP, constituted the only cohort to show an increase in performance. The significant effect of draft round and position type on RTP may be caused by a combination of differences in talent levels and in opportunities given to returning to play.


#2 Recurrent Labral Tearing on Magnetic Resonance Imaging Is Not Predictive of Diminished Participation Among National Football League Athletes
Reference: Arthroscopy. 2017 Sep 30. pii: S0749-8063(17)30703-X. doi: 10.1016/j.arthro.2017.07.007. [Epub ahead of print]
Authors: Knapik DM, Gebhart JJ, Sheehan J, Tanenbaum JE, Salata MJ, Voos JE
Summary: The purpose was to investigate the prevalence of shoulder labral repair and utility of magnetic resonance imaging (MRI) in determining the risks of recurrent labral tearing and impact on future participation in the National Football League (NFL). Athletes invited to the NFL Combine between 2012 and 2015 were retrospectively reviewed. Athletes with a history of labral repair and MRI of the operative shoulder at the Combine were included in the study for further analysis, excluding athletes without a history of labral repair, labral repair without MRI at the Combine, additional procedure to the operative shoulder, or athletes still undergoing rehabilitation at the time of the Combine after labral repair. All MRIs were reviewed to determine initial labral repair location, the presence of recurrent tearing, and any concomitant shoulder pathology. Prospective information on future NFL participation in regard to draft status, games played, and games started in the athlete's first NFL season after the Combine was compared between athletes with a history of labral repair with and without recurrent tearing versus all other athletes participating in the Combine. A total of 132 (10.1%) athletes underwent 146 shoulder labral repair procedures before the NFL Combine, of whom 32% (n = 39 athletes, n = 46 shoulders) had recurrent labral tears on MRI. Athletes with recurrent tears were more likely to have undergone bilateral labral repairs (P = .048) and possess concomitant shoulder pathology (P < .001). Recurrent labral tearing was significantly more common in the posterior labrum in athletes with a history of posterior labral repairs (P = .032). Prospective participation in the NFL in terms of games played (P = .38) or started (P = .98) was not significantly reduced in athletes with a history of labral repair compared with those without repair. Participation was not diminished in athletes with recurrent labral tears compared with those with intact repairs or those with evidence of degenerative joint disease. Athletes invited to the NFL Scouting Combine with a history of bilateral repair, posterior labral repair, and concomitant shoulder pathology are at high risk of recurrent labral tearing on MRI. No significant reduction in NFL participation the year after the Combine was seen in athletes with a history of labral repair, recurrent labral tearing, or degenerative joint disease who were successfully drafted into the NFL. In athletes with a history of labral repair, assessment of labral integrity on MRI alone is not predictive of future short-term participation.

Wed

11

Oct

2017

Football is...(#24)

Football specific cutting maneuvers for muscular development.

Mon

09

Oct

2017

Football is...(#23)

Knee stability for movements.

Sun

08

Oct

2017

Football is...(#22)

Number of players affect intensity in SSG

Fri

06

Oct

2017

Football is...(#21)

Appropriate training load = performance + injury prevention

Wed

04

Oct

2017

Football is...(#20)

One option to train for keeping the ball in offensive 1 vs. 1.

Wed

04

Oct

2017

Latest research in football - week 39 - 2017

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Resting metabolic rate of Indian Junior Soccer players: Testing agreement between measured versus selected predictive equations
Reference: Am J Hum Biol. 2017 Sep 30. doi: 10.1002/ajhb.23066. [Epub ahead of print]
Authors: Cherian KS, Shahkar F, Sainoji A, Balakrishna N, Yagnambhatt VR
Summary: Owing to a dearth of research related to Resting Metabolic Rate (RMR) among adolescent athletes in India, our study aimed to document RMR among junior soccer players (JSP) and to identify suitable RMR predictive models for JSP from nine existing equations. Forty Indian JSP (Boys = 21, Girls = 19) representing the under-12 and under-16 age categories were assessed for body composition (skinfold technique) and RMR (oxycon mobile). Two-way ANOVA and ANCOVA were used to examine the differences across age and sex. Bland-Altman plot was used to test agreement between measured vs. predicted RMR using the equations of Cunningham (, The American Journal of Clinical Nutrition, 33), Soares et al. (, European Journal of Clinical Nutrition, 47; 1998, British Journal of Nutrition, 79), Henry (, Public Health Nutrition, 8), and Patil and Bharadwaj (, Journal of Postgraduate Medicine, 59) for non-athletic populations and the equations of De Lorenzo et al. (, The Journal of Sports Medicine and Physical Fitness, 39), Wong et al. (, Singapore Medical Journal, 53), and ten Haaf & Weijs (, PloS One, 9) for adult athletes. RMR showed significant (P < .01) sex differences (Boys: 1343 ± 297.1; Girls: 1135 ± 116.7 kcal·day-1 ). While RMR values adjusted for fat-free mass (FFM) were similar across age and sex. The equation of Soares et al. (, British Journal of Nutrition, 79) for girls and Wong et al. (, Singapore Medical Journal, 53) for boys showed better RMR predictability. FFM explained variation in RMR across age and sex. The FFM-based Soares et al. (, British Journal of Nutrition, 79) equation for girls and body weight-based Wong et al. (, Singapore Medical Journal, 53) equation for boys are best suited for predicting RMR


#2 Effects of age on the soccer-specific cognitive-motor performance of elite young soccer players: Comparison between objective measurements and coaches' evaluation
Reference: PLoS One. 2017 Sep 27;12(9):e0185460. doi: 10.1371/journal.pone.0185460. eCollection 2017.
Authors: Hicheur H, Chauvin A, Chassot S, Cheneviere X, Taube W
Download link: http://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0185460&type=printable
Summary: The cognitive-motor performance (CMP), defined here as the capacity to rapidly use sensory information and transfer it into efficient motor output, represents a major contributor to performance in almost all sports, including soccer. Here, we used a high-technology system (COGNIFOOT) which combines a visual environment simulator fully synchronized with a motion capture system. This system allowed us to measure objective real-time CMP parameters (passing accuracy/speed and response times) in a large turf-artificial grass playfield. Forty-six (46) young elite soccer players (including 2 female players) aged between 11 and 16 years who belonged to the same youth soccer academy were tested. Each player had to pass the ball as fast and as accurately as possible towards visual targets projected onto a large screen located 5.32 meters in front of him (a short pass situation). We observed a linear age-related increase in the CMP: the passing accuracy, speed and reactiveness of players improved by 4 centimeters, 2.3 km/h and 30 milliseconds per year of age, respectively. These data were converted into 5 point-scales and compared to the judgement of expert coaches, who also used a 5 point-scale to evaluate the same CMP parameters but based on their experience with the players during games and training. The objectively-measured age-related CMP changes were also observed in expert coaches' judgments although these were more variable across coaches and age categories. This demonstrates that high-technology systems like COGNIFOOT can be used in complement to traditional approaches of talent identification and to objectively monitor the progress of soccer players throughout a cognitive-motor training cycle.


#3 Comparison of Thigh Muscle Strain Occurrence and Injury Patterns between Male and Female High School Soccer-Athletes
Reference: J Sport Rehabil. 2017 Sep 27:1-35. doi: 10.1123/jsr.2016-0178. [Epub ahead of print]
Authors: Cross KM, Gurka KK, Saliba S, Conaway M, Hertel J
Summary: Thigh muscles strains are among the most common injuries in high school soccer for both males and females. Similar results have been reported among collegiate soccer players, specifically for hamstring strains. In collegiate soccer, males have a higher injury rate than women although they share common injury characteristics. Currently, no studies exist comparing the injury rate or injury characteristics of thigh muscle strains between sexes playing high school soccer. The objective of the study was to compare thigh muscle strain injury rates and injury event characteristics among sexes participating in high school soccer. High school soccer athletes who had a thigh muscle strain were involved in this study. Injury rates of thigh muscle strains were calculated between sexes. The occurrence of the following variables during a thigh muscle injury were compared between sexes: grade level, age, level of play, event type, time of practice, time of competition, basic injury mechanism, soccer activity, player position, field location, practice type, time of season. Males had a lower injury rate of thigh muscle strains during competition than females. (RR=0.66; 95% CI, 0.47, 0.93) No differences between sexes existed in the distribution of first-time or recurrent event characteristics. When combining sexes, recurrent strains (93%) occurred more frequently on the offensive side of the field than first-time strains (59%), P<0.0001. The majority of strains occurred among the varsity players (71%), during running activities (60%) and during practices (58%). Males were less likely to sustain a thigh muscle strain during competitions, but no other differences existed between sexes. The events surrounding all thigh muscle strains may be described with some common properties. Consideration of these characteristics may assist in the development of preventive and rehabilitative programs as well as direct future research on thigh muscle strains among high school soccer players.


#4 Locomotor and Heart Rate Responses of Floaters During Small-Sided Games in Elite Soccer Players: Effect of Pitch Size and Inclusion of Goal Keepers
Reference: Int J Sports Physiol Perform. 2017 Sep 27:1-13. doi: 10.1123/ijspp.2017-0340. [Epub ahead of print]
Authors: Lacome M, Simpson BM, Cholley Y, Buchheit M
Summary: The purpose was to (1) compare the locomotor and heart rate responses between floaters and regular players during both small and large small sided games (SSGs) and (2) examine whether the type of game (i.e., game simulation vs possession game) affects the magnitude of the difference between floaters and regular players. Data were collected in 41 players belonging to an elite French football team during three consecutive seasons (2014-2017). 5-Hz GPS were used to collect all training data, with the Athletic Data Innovation analyser (v5.4.1.514, Sydney, Australia) used to derive total distance (m), high-speed distance (> 14.4 km.h-1, m) and external mechanical load (MechL, a.u). All SSGs included exclusively one floater, and were divided into two main categories, according to the participation of goal-keepers (GK) (game simulation, GS) or not (possession games, PO) and then further divided into small and large (>100 m2/player) SSGs based on the area per player ratio. Locomotor activity and mechanical load performed were likely-to-most likely lower (moderate to large magnitude) in floaters compared with regular players, while differences in HR responses were unclear to possibly higher (small) in floaters. The magnitude of the difference in locomotor activity and MechL between floaters and regular players was substantially greater during GS compared with PO. Compared with regular players, floaters present decreased external load (both locomotor and MechL) despite unclear to possibly slightly higher HR responses during SSGs. Moreover, the responses of floaters compared with regular players are not consistent across different sizes of SSGs, with greater differences during GS than PO.


#5 Successful return to play following adductor longus proximal tendon rupture in professional soccer without re-injury at 12 months: A case report
Reference: J Back Musculoskelet Rehabil. 2017 Sep 8. doi: 10.3233/BMR-170857. [Epub ahead of print]
Authors: Gozubuyuk OB, Moen MH, Akman M, Ipseftel I, Karakuzu A
Summary: Treatment of total ruptures of adductor longus is challenging in professional sports. Time for return to pre-injury level as well as re-injury rates are of concern and surgical and conservative treatment approaches are debated; yet no consensus approach described for professional athletes. We present a case of a professional soccer player who experienced a rupture in his left adductor longus proximal tendon during a game and was treated conservatively. This case was followed-up during clinical assessment, imaging and strength testing until and after return to play. Primary outcome measure was the return to standard play condition at his pre-injury level without any functional deficits, measured by isokinetic testing. Second outcome measure was the recurrence. No recurrence was observed during the first year of follow-up. Total ruptures are very challenging for both the physician and the player to make a quick decision due to minimal or lack of pain. Functional outcomes are almost identical although operative treatments need longer time to return to play. This case report adds another example to the literature of a successful return to play after non-operative treatment of adductor longus rupture at elite level soccer.


#6 Is strength-training frequency a key factor to develop performance adaptations in young elite soccer players?
Reference: Eur J Sport Sci. 2017 Sep 24:1-11. doi: 10.1080/17461391.2017.1378372. [Epub ahead of print]
Authors: Otero-Esquina C, de Hoyo Lora M, Gonzalo-Skok O, Dominguez-Cobo S, Sanchez H
Summary: The aim of this study was to analyse the effects of a combined strength-training programme (full-back squat, YoYoTM leg curl, plyometrics and sled towing exercises) on performance in elite young soccer players and to examine the effects when this training programme was performed one or two days per week. Thirty-six male soccer players (U-17 to U-19) were recruited and assigned to experimental groups (EXP1: 1 s w-1; EXP2: 2 s w-1) or a control group (CON). Performance was assessed through a countermovement jump (CMJ) test (relative peak power [CMJPP] and CMJ height [CMJH]), a 20-m linear sprint test with split-times at 10-m, and a change of direction test (V-cut test) 1 week before starting the training programme and also 1 week after performing such training programme. Within-group analysis showed substantial improvements in CMJ variables (ES: 0.39-0.81) and COD (ES: 0.70 and 0.76) in EXP1 and EXP2, while EXP2 also showed substantial enhancements in all linear sprinting tests (ES: 0.43-0.52). Between-group analysis showed substantially greater improvements in CMJ variables (ES: 0.39-0.68) in experimental groups in comparison to CON. Furthermore, EXP2 achieved a substantial better performance in 20-m (ES: 0.48-0.64) than EXP1 and CON. Finally, EXP2 also showed greater enhancements in 10-m (ES: 0.50) and V-cut test (ES: 0.52) than EXP1. In conclusion, the combined strength-training programme improved jumping ability, independently of training frequency, though the achievement of two sessions per week also enhanced sprinting abilities (linear and COD) in young soccer players.


#7 Neuromuscular responses and physiological patterns during a soccer simulation protocol. Artificial turf versus natural grass
Reference: J Sports Med Phys Fitness. 2017 Sep 22. doi: 10.23736/S0022-4707.17.07768-4. [Epub ahead of print]
Authors: Lopez-Fernandez J, Garcia-Unanue J, Sanchez-Sanchez J, Leon M, Hernando E, Gallardo L
Summary: Latest studies suggest similar performance of soccer players either on artificial turf (AT) or natural grass (NG). However, it is not clear if their muscular and physiological responses are also similar on both surfaces. This research aims to assess the influence of game surface on physiological patterns and neuromuscular responses of soccer players during a soccer simulation protocol (SSP) that incorporates repeated sprints and nonlinear actions at maximum speed. Sixteen amateur soccer players completed three bouts of the SSP on both AT and NG. The mechanical behaviour of both surfaces was recorded and the order was randomly established for each player. The physiological responses were measured during the SSP. A contra-movement jump and a tensiomyography analysis of the rectus femurs (RF) and biceps femoris (BF) were assessed right before and right after the SSP. Both surfaces presented different mechanical properties. No differences among either surfaces or bouts were found for heart rate (HR) peak and HR mean (p >0.05). While the half-relaxation time of the RF on NG decreased after the SSP (right-leg:-44.430 ms; p = 0.049; left-leg: -52.131 ms; p = 0.008), the sustain time of the BF decreased after the SSP on AT (right-leg: +64.868 ms; p = 0.007; left-leg: +87.564 ms; p<0.001). No differences between surfaces were found for the contra-movement jump. The mechanical behaviour of both surfaces does not differ enough to cause different physiological and neuromuscular responses. Playing on AT should cause similar neuromuscular responses to NG.


#8 Variability of GPS-derived running performance during official matches in elite professional soccer players
Reference: J Sports Med Phys Fitness. 2017 Sep 22. doi: 10.23736/S0022-4707.17.07500-4. [Epub ahead of print]
Authors: Al Haddad H, Mendez-Villanueva A, Torreno N, Munguia-Izquierdo D, Suarez-Arrones L
Summary: The aim of this study was to assess the match-to-match variability obtained using GPS devices, collected during official games in professional soccer players. GPS-derived data from nineteen elite soccer players were collected over two consecutive seasons. Time-motion data for players with more than five full-match were analyzed (n=202). Total distance covered (TD), TD >13-18 km/h, TD >18-21 km/h, TD >21 km/h, number of acceleration >2.5-4 m.s-2 and >4 m.s-2 were calculated. The match-to-match variation in running activity was assessed by the typical error expressed as a coefficient of variation (CV,%) and the magnitude of the CV was calculated (effect size). When all players were pooled together, CVs ranged from 5% to 77% (first half) and from 5% to 90% (second half), for TD and number of acceleration >4 m.s-2, and the magnitude of the CVs were rated from small to moderate (effect size = 0.57-0.98). The CVs were likely to increase with running/acceleration intensity, and were likely to differ between playing positions (e.g., TD > 13-18 km/h 3.4% for second strikers vs 14.2% for strikers and 14.9% for wide-defenders vs 9.7% for wide-midfielders). Present findings indicate that variability in players' running performance is high in some variables and likely position-dependent. Such variability should be taken into account when using these variables to prescribe and/or monitor training intensity/load. GPS-derived match-to-match variability in official games' locomotor performance of professional soccer players is high in some variables, particularly for high-speed running, due to the complexity of match running performance and its most influential factors and reliability of the devices.


#9 Adding a post-training FIFA 11+ exercise program to the pre-training FIFA 11+ injury prevention program reduces injury rates among male amateur soccer players: a cluster-randomised trial
Reference: J Physiother. 2017 Sep 20. pii: S1836-9553(17)30102-9. doi: 10.1016/j.jphys.2017.08.004. [Epub ahead of print]
Authors: Al Attar WSA, Soomro N, Pappas E, Sinclair PJ, Sanders RH
Download link: http://www.journalofphysiotherapy.com/article/S1836-9553(17)30102-9/pdf
Summary: Does adding a post-training Fédération Internationale de Football Association (FIFA) 11+ exercise program to the pre-training FIFA 11+ injury prevention program reduce injury rates among male amateur soccer players? Twenty-one teams of male amateur soccer players aged 14 to 35 years were randomly assigned to the experimental group (n=10 teams, 160 players) or the control group (n=11 teams, 184 players). Both groups performed pre-training FIFA 11+ exercises for 20minutes. The experimental group also performed post-training FIFA 11+ exercises for 10minutes. The primary outcomes measures were incidence of overall injury, incidence of initial and recurrent injury, and injury severity. The secondary outcome measure was compliance to the experimental intervention (pre and post FIFA 11+ program) and the control intervention (pre FIFA 11+ program). During one season, 26 injuries (team mean=0.081 injuries/1000 exposure hours, SD=0.064) were reported in the experimental group, and 82 injuries were reported in the control group (team mean=0.324 injuries/1000hours, SD=0.084). Generalised Estimating Equations were applied with an intention-to-treat analysis. The pre and post FIFA 11+ program reduced the total number of injuries (χ2 (1)=11.549, p=0.001) and the incidence of initial injury (χ2 (2)=8.987, p=0.003) significantly more than the pre FIFA 11+ program alone. However, the odds of suffering a recurrent injury were not different between the two groups (χ2 (1)=2.350, p=0.125). Moreover, the severity level of injuries was not dependent upon whether or not the pre and post FIFA 11+ program was implemented (χ2 (1)=0.016, p=0.898). Implementation of the FIFA 11+ program pre-training and post-training reduced overall injury rates in male amateur soccer players more than the pre FIFA 11+ program alone.


#10 Symptoms of common mental disorders and related stressors in Danish professional football and handball
Reference: Eur J Sport Sci. 2017 Sep 29:1-7. doi: 10.1080/17461391.2017.1381768. [Epub ahead of print]
Authors: Kilic O, Aoki H, Haagensen R, Jensen C, Johnson U, Kerkhoffs GMMJ, Gouttebarge V
Summary: The aim of the study was twofold, namely (i) to determine the prevalence of symptoms of common mental disorders (CMDs) among current and retired professional football and handball players and (ii) to explore the relationship of psychosocial stressors with the outcome measures under study. A total of 1155 players were enrolled in an observational study based on a cross-sectional design. Questionnaires based on validated scales were set up and distributed among current and retired professional football and handball players by the Danish football and handball players' union. In professional football, the highest prevalence (4 weeks) of symptoms of CMDs was 18% and 19% for anxiety/depression among current and retired players, respectively. In professional handball, the highest prevalence (4 weeks) of symptoms of CMDs was 26% and 16% for anxiety/depression among current and retired players, respectively. For both the current and retired professional football and handball players, a higher number of severe injuries and recent adverse life events (LE) were related to the presence of symptoms of CMD. Players exposed to severe injuries and/or recent adverse LE were 20-50% times more likely to report symptoms of CMD. The results suggest that it is possible to recognize the population of professional athletes that are more likely to develop symptoms of CMD. This could create the opportunity to intervene preventively on athletes that suffered from severe injury and/or recent adverse LE that could lead to a faster and safer recovery and psychological readiness to return to play.


American Football
#1 Evaluating behavioral skills training to teach safe tackling skills to youth football players
Reference:  J Appl Behav Anal. 2017 Sep 20. doi: 10.1002/jaba.412. [Epub ahead of print]
Authors: Tai SSM, Miltenberger RG
Summary: With concussion rates on the rise for football players, there is a need for further research to increase skills and decrease injuries. Behavioral skills training is effective in teaching a wide variety of skills but has yet to be studied in the sports setting. We evaluated behavioral skills training to teach safer tackling techniques to six participants from a Pop Warner football team. Safer tackling techniques increased during practice and generalized to games for the two participants who had opportunities to tackle in games.


#2 Return to play after shoulder instability in National Football League athletes
Reference: J Shoulder Elbow Surg. 2017 Sep 20. pii: S1058-2746(17)30448-2. doi: 10.1016/j.jse.2017.07.027. [Epub ahead of print]
Authors: Okoroha KR, Taylor KA, Marshall NE, Keller RA, Fidai M, Mahan MC, Varma V, Moutzouros V
Summary: We hypothesized that National Football League (NFL) players sustaining a shoulder destabilizing injury could return to play (RTP) successfully at a high rate regardless of treatment type. We identified and evaluated 83 NFL players who sustained an in-season shoulder instability event while playing in the NFL. NFL RTP, incidence of surgery, time to RTP, recurrent instability events, seasons/games played after the injury, and demographic data were collected. Overall RTP was determined, and players who did and did not undergo operative repair were compared. Ninety-two percent of NFL players returned to NFL regular season play at a median of 0.0 weeks in those sustaining a shoulder subluxation and 3.0 weeks in those sustaining a dislocation who did not undergo surgical repair (P = .029). Players who underwent operative repair returned to play at a median of 39.3 weeks. Forty-seven percent of players had a recurrent instability event. For players who were able to RTP, those who underwent surgical repair (31%) had a lower recurrence rate (26% vs. 55%, P = .021) and longer interval between a recurrent instability event after RTP (14.7 vs. 2.5 weeks, P = .050). There is a high rate of RTP after shoulder instability events in NFL players. Players who sustain shoulder subluxations RTP faster but are more likely to experience recurrent instability than those with shoulder dislocations. Surgical stabilization of the shoulder after an instability event decreases the chances of a second instability event and affords a player a greater interval between the initial injury and a recurrent event.


#3 Concussion Nondisclosure During Professional Career Among a Cohort of Former National Football League Athletes
Reference: Am J Sports Med. 2017 Sep 1:363546517728264. doi: 10.1177/0363546517728264. [Epub ahead of print]
Authors: Kerr ZY, Register-Mihalik JK, Kay MC, DeFreese JD, Marshall SW, Guskiewicz KM
Summary: Despite a focus on the incidence and effects of concussion, nondisclosure of sports-related concussions among retired players from the National Football League (NFL) has yet to be examined. The purpose was to examine the prevalence of and factors associated with nondisclosure of sports-related concussions in former NFL athletes. A sample of 829 former NFL players completed a general health survey. This historical cohort included players who had played before World War II to 2001. Respondents retrospectively recalled sports-related concussions that they sustained during their professional careers and whether at least one of these sports-related concussions was not reported to medical staff. We computed the prevalence of nondisclosure among those recalling sport-related concussions during their professional careers. Multivariable binomial regression estimated adjusted prevalence ratios (PR) with 95% confidence intervals (CIs) controlling for race/ethnicity, number of years played, primary position played, professional career concussion history, and playing era. Playing era was categorized by whether the majority of a player's career was before or after a 1976 rule change to limit contact ("spearing"). Overall, 417 (50.3%) respondents reported they had sustained a concussion and did not inform medical staff at least once during their professional playing career. Nonwhite respondents had a higher prevalence of nondisclosure than white/non-Hispanic respondents (adjusted PR = 1.19; 95% CI, 1.02-1.38). An interaction between professional career concussion history and playing era was also found ( P = .08). Compared with those in the pre-spearing rule change group with 1 or 2 concussions, all other groups had larger prevalences of nondisclosure (increases ranging from 41% to 153% in multivariable models). Across concussion strata, nondisclosure prevalence was generally higher in the post-spearing rule change group than the pre-spearing rule change group, with the largest differences found among those with 1 or 2 concussions or those with 3 or 4 concussions. A large proportion of former NFL players in this historical cohort reported at least one instance of not disclosing sports-related concussions to medical staff. Future research on concussion nondisclosure needs to identify mechanisms to improve football players' intentions to disclose concussion-related symptoms to health care providers and to equip health care providers with more effective strategies for timely identification of concussion.


#5 A Narrative Review of the Physical Demands and Injury Incidence in American Football: Application of Current Knowledge and Practices in Workload Management
Reference: Sports Med. 2017 Sep 25. doi: 10.1007/s40279-017-0783-2. [Epub ahead of print]
Authors: Edwards T, Spiteri T, Piggott B, Haff GG, Joyce C
Summary: The sport of American football (AmF) exposes athletes to high-velocity movements and frequent collisions during competition and training, placing them at risk of contact and non-contact injury. Due to the combative nature of the game, the majority of injuries are caused by player contact; however, a significant number are also non-contact soft-tissue injuries. The literature suggests that this mechanism of injury can be prevented through workload monitoring and management. The recent introduction of microtechnology into AmF allows practitioners and coaches to quantify the external workload of training and competition to further understand the demands of the sport. Significant workload differences exist between positions during training and competition; coupling this with large differences in anthropometric and physical characteristics between and within positions suggests that the training response and physiological adaptations will be highly individual. Effective athlete monitoring and management allows practitioners and coaches to identify how athletes are coping with the prescribed training load and, subsequently, if they are prepared for competition. Several evidence-based principles exist that can be adapted and applied to AmF and could decrease the risk of injury and optimise athletic performance.


#6 The Epidemiology of Overuse Conditions in Youth Football and High School Football Players
Reference: J Athl Train. 2017 Sep 26. doi: 10.4085/1062-6050-52.10.04. [Epub ahead of print]
Authors: Morris K, Simon J, Grooms DR, Starkey C, Dompier TP, Kerr ZY
Summary: High-intensity sport training at the youth level has led to increased concern for overuse conditions. Few researchers have examined overuse conditions in youth sports. The purpose was to examine the rates, risks, and distributions of overuse conditions between youth and high school football. The Youth Football Safety Study (YFSS) investigated youth football athletes from age 5 to 14 years. The National Athletic Treatment, Injury and Outcomes Network (NATION) focused on high school football athletes 14 to 18 years old. The YFSS data consisted of 210 team-seasons, and the NATION data consisted of 138 team-seasons. Athletic trainers collected football injury and exposure data during the 2012 and 2013 seasons. Injury rates, risks, and distributions were calculated, with injury rate ratios, risk ratios, and injury proportion ratios with 95% confidence intervals (CIs) comparing high school and youth football players. The YFSS reported 1488 injuries, of which 53 (3.6%) were overuse conditions. The NATION reported 12 013 injuries, of which 339 (2.8%) were overuse conditions. The overuse condition rate did not differ between high school and youth football (3.93 versus 3.72/10 000 athlete exposures; injury rate ratio = 1.06; 95% CI = 0.79, 1.41). However, the 1-season risk of overuse condition was higher in high school than in youth football players (2.66% versus 1.05%; risk ratio = 2.53; 95% CI = 1.84, 3.47). Compared with high school football players, youth football players had greater proportions of overuse conditions that were nontime loss (ie, <24 hours participation-restriction time; 83.0% versus 67.0%; injury proportion ratio = 1.24; 95% CI = 1.07, 1.43) and affecting the lower extremity (92.5% versus 62.5%; injury proportion ratio = 1.48; 95% CI = 1.32, 1.65). Overuse conditions may not present a primary concern in youth and high school football players. However, differences existed between the 2 levels of competition. Although additional research on the incidence of overuse conditions across all youth and high school sports is needed, these findings may highlight the need for programming that is specific to competition level.


#7 Characteristics and Outcomes of Arthroscopic Femoroacetabular Impingement Surgery in the National Football League
Reference: Am J Sports Med. 2017 Sep 1:363546517729163. doi: 10.1177/0363546517729163. [Epub ahead of print]
Authors: Nwachukwu BU, Bedi A, Premkumar A, Draovitch P, Kelly BT
Summary: Previous studies have reported that hip abnormalities may account for 10% of injuries in professional football players. The effect of femoroacetabular impingement (FAI) and arthroscopic FAI surgery in National Football League (NFL) athletes has not been well studied. The purpose was to investigate the effect of arthroscopic FAI surgery on return to play (RTP) and RTP performance in NFL players. NFL athletes undergoing arthroscopic FAI surgery at a single institution between 2006 and 2014 were identified. Medical records were reviewed for demographic, clinical, and operative variables. RTP and RTP performance were assessed based on a review of publicly available NFL player statistics. RTP and RTP performance data included time to RTP; games played before and after the injury; yearly total yards and touchdowns for offensive players; and yearly total tackles, sacks, and interceptions for defensive players. The offensive power rating (OPR = [total yards/10] + [total touchdowns × 6]) and defensive power rating (DPR = total tackles + [total sacks × 2] + [total interceptions × 2]) were calculated. Paired t tests comparing preinjury and postinjury seasons were performed. A matched cohort of NFL players was created to compare trends for OPR, DPR, and career longevity. Forty-eight hips in 40 NFL players (mean age, 25.6 years) with symptomatic FAI were included; 8 players underwent staged bilateral hip arthroscopic procedures. The majority of players were offensive (n = 24; 60.0%), with offensive lineman (n = 11; 27.5%) being the most common of all positions. Of the 48 included hips, all had labral tears, and 41 (85.4%) underwent labral repair. Forty-two of the 48 hips (87.5%) underwent cam decompression, and 10 (20.8%) underwent rim decompression. Of the 40 included players, 37 (92.5%) achieved RTP to professional competition after their hip arthroscopic surgery at a mean of 6.0 months. Before the injury, included patients played in a mean of 11.0 games compared with 9.5 games in their postoperative season ( P = .26). The mean OPR and DPR demonstrated a nonsignificant decline in the postoperative season (preinjury OPR, 40.2; postinjury OPR, 32.3; P = .34) (preinjury DPR, 49.6; postinjury DPR, 36.4; P = .10). A similar decline in the OPR and DPR across seasons was observed in the control group. NFL athletes played, on average, 3.3 ± 1.5 seasons after undergoing hip arthroscopic surgery; this was not significantly different from the controls (2.5 ± 1.5 seasons; P = .47). There was no significant difference in mean annual salaries based on contracts negotiated before the injury and the first negotiated contract after surgery ($3.3 million vs $3.6 million, respectively; P = .58). There was a very high rate of RTP in the NFL after arthroscopic FAI surgery; this rate is higher than what has been previously reported for other orthopaedic procedures in NFL athletes. Additionally, these NFL athletes achieved RTP at a faster time frame (6 months) than previously reported for other procedures. These findings have important implications for counseling elite football players about the expected outcome of arthroscopic FAI surgery.


#8 Daily Fantasy Football and Self-Reported Problem Behavior in the United States
Reference: J Gambl Stud. 2017 Sep 26. doi: 10.1007/s10899-017-9720-4. [Epub ahead of print]
Authors: Dwyer B, Shapiro SL, Drayer J
Summary: Traditional, season-long fantasy sport participation has grown considerably since the late 1990s, and in an attempt to capitalize on this growing demand, daily fantasy sports (DFS) providers have created a new game where money changes hands instantly. This change has led some legal commentators and state agencies to believe the game is a form of Internet gambling similar to online poker, blackjack, and sports wagering, and thus, it requires increased regulation or even prohibition. Little is known, however, about the gambling behavior associated with DFS participation. Thus, the purpose of the current study was to examine problem gambling severity in conjunction with DFS participant motives, perceptions, and consumption behavior. Over 500 DFS participants were surveyed, and the results suggest DFS participants behave similarly with participants in other forms of gambling activities. In addition, the findings suggest additional consumer protections may be needed to prevent further problem behavior such as chasing.


#9 Lifetime Prevalence of Injuries in Incoming Division I Collegiate Football Players
Reference: Phys Sportsmed. 2017 Sep 27. doi: 10.1080/00913847.2017.1386068. [Epub ahead of print]
Authors: Sarac N, Haynes W, Pedroza A, Kaeding C, Borchers J
Summary: The purpose of this study is to determine the lifetime prevalence of past injuries in incoming first year football players in a Division 1 college football team. Pre-participation questionnaires from 605 first-year football players over 20 years (1996-2015) were examined to determine the prevalence of concussions, stingers, fractures, and musculoskeletal surgeries sustained before playing at the collegiate level. Players were grouped by position: wide receiver and defensive back (WR/DB), offensive and defensive linemen (OL/DL), all other positions (OP), and unknown (UKN). Prevalence of injuries by year and position was compared using Pearson's χ2 Test (p<0.05). The reported lifetime prevalence is as follows: concussion (21%), stinger (23%), musculoskeletal surgery (23%), and fracture (44%). There were no significant differences in lifetime prevalence of concussions (p=0.49), stingers (p=0.31), fractures (p=0.60), or musculoskeletal surgeries (p=0.97) based on position. There were also no significant differences in the lifetime prevalence of concussions (p=0.14), musculoskeletal surgeries (p=0.50), or fractures (p=0.59) based on year. However, there was a significant difference in the lifetime prevalence of stingers based on year (p<0.001). There was an expectation to observe an increase in injury prevalence by entering year, but this was not seen. A decrease in stingers was actually observed, but there was no significant difference among any other injury recorded. These results do not support the perception that football injuries are on the rise. Under reporting is a significant concern as players may fear disqualification or that they are evaluated by the coaching staff based on their medical history. More research is needed to confirm lifetime injury prevalence and evaluate differences over time among football players.


#10 Distal Fibula Fractures in National Football League Athletes
Reference: Orthop J Sports Med. 2017 Sep 8;5(9):2325967117726515. doi: 10.1177/2325967117726515. eCollection 2017 Sep.
Authors: Werner BC, Mack C, Franke K, Barnes RP, Warren RF, Rodeo SA
Summary: Despite the frequency of distal fibula fractures in elite athletes and the significant potential impact on the athletes' season and future careers, little data exist characterizing the epidemiology of these injuries or, more importantly, return to competition. The purpose was to (1) evaluate the incidence of acute distal fibula fractures in National Football League (NFL) athletes, including isolated distal fibula and combined ankle fracture patterns; (2) analyze distal fibula fracture rates in NFL athletes by position, type of play, and contact type; (3) determine the rates of distal fibula fracture surgery in NFL athletes; and (4) report the days missed due to distal fibula fractures in NFL athletes. A retrospective review of distal fibula fractures reported to the NFL from 2000 to 2014 was performed using the NFL Injury Surveillance System. All distal fibula fractures were included, along with isolated and combined fracture patterns. Stress fractures and proximal fibula fractures were excluded. Epidemiological data and rates of surgery were determined. Return to sport was calculated and stratified by injury pattern and management. Overall, 237 distal fibula fractures in NFL athletes from 2000 to 2014 were included; 197 (83%) were isolated distal fibula fractures. A mean of 16 distal fibula fractures occurred each year (median, 16 per year). Fractures occurred most frequently on running (38%) and passing (24%) plays, but the frequency was next highest on kickoffs (16%), despite the relative infrequency of kickoffs during the average game compared with other play types. Surgery was reported for more than half of all distal fibula fractures (n = 128, 54%). Overall, patients who underwent surgery missed significantly more days (mean, 123.8 days) than players who did not undergo surgery (mean, 75.3 days) (P < .001). Players with isolated distal fibula fractures had significantly fewer days missed (mean, 93.6 days) compared with those with combined patterns (mean, 132.3 days) (P = .0004). Fibula fractures affect a number of NFL athletes and result in significant time missed from competition. Further research is required to determine the optimal management of fibula fractures in NFL athletes. In this study, time to return to play depended on both the fracture pattern and whether surgery was required and ranged from 72 to 145 days.

Tue

03

Oct

2017

Football is...(#19)

Youth players - every Training session 1.000 touches!

Mon

02

Oct

2017

Football...(#18)

Dynamic stretches done correctly are important during the warm-up.

Mon

02

Oct

2017

German Society of Sport Science - Section Football

The German Sport Science Association – Section Football had its annual meeting at Ruhr University Bochum from 28.-30.9.2017.

I attended the conference and the important slides from the one and only english presentation from the one and only Aaron Coutts about “Developing athlete monitoring systems for football: theoretical foundations” are shown below.

Thu

28

Sep

2017

Football is...(#17)

Attacking third entry is crucial for scoring goals.

Thu

28

Sep

2017

Latest research in football - week 38 - 2017

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Elite Youth Soccer Players' Physiological Responses, Time-Motion Characteristics, and Game Performance in 4 vs. 4 Small-Sided Games: The Influence of Coach Feedback
Reference: J Strength Cond Res. 2017 Oct;31(10):2652-2658. doi: 10.1519/JSC.0000000000001717.
Authors: Brandes M, Elvers S
Summary: The purpose of this study was to determine the impact of mild vs. strongly pushed coach feedback on the physiological response, ratio of perceived exertion (RPE), and time-motion characteristics in soccer training with small-sided games (SSGs). Sixteen elite youth soccer players (aged 17.2 ± 0.7 years, V[Combining Dot Above]O2max 62.1 ± 3.8 ml·kg·min) played two 4 vs. 4 small-sided games each. In random order, the coach provided a mild, unobtrusive, or a strongly pushed feedback throughout the game. Physiological measurements included heart rate expressed in mean values and intensity zones, blood lactate concentration, and RPE. The distance traveled, number of sprints, and work:rest ratio were captured by global positioning systems at 5 Hz. Game performance, such as volume of play and efficacy index, was estimated using the Team Sports Assessment Procedure. No differences were found for the physiological response and time-motion characteristics, but effect sizes demonstrated an increase in RPE (+0.4, p = 0.27) and a decrease in game performance (e.g., volume of play, -2.5, p = 0.08) under pushed feedback. Although a pushed feedback raises RPE, it negatively affected the players' game performance, without necessarily provoking higher physiological responses. These results should help coaches to understand that modifying the type of feedback provided during SSG does not impact the physiological response if SSG are already played with high intensity but that the feedback affects RPE and game performance. To keep a better game performance, soccer coaches are encouraged to provide smooth feedback during SSG.


#2 Hopping and Landing Performance in Male Youth Soccer Players: Effects of Age and Maturation
Reference: Int J Sports Med. 2017 Sep 20. doi: 10.1055/s-0043-114009. [Epub ahead of print]
Authors: Read PJ, Oliver JL, Myer G, De Ste Croix M, Lloyd R
Summary: Quantifying hopping and landing performances can assist coaches in identifying young male soccer players who may be at increased risk of injury. The influence of chronological age and maturation on these measures in this population is unknown. Single leg hop for distance (SLHD) and 75% horizontal hop and stick landing force (75%Hop) were examined in a cross-sectional sample (N=400) of elite male youth soccer players. Between-group differences for both chronological age (U11-U18) and stage of maturation (pre-, circa- or post-peak height velocity (PHV)) were analyzed. Absolute 75%Hop increased with both age and maturation. Apart from the U18s, pre-PHV and U11-U12 players displayed the greatest relative landing forces compared to all other groups (p<0.001; d=0.56-0.93). Absolute and relative SLHD were greatest in the U18s and post-PHV players (p<0.001; d=0.35-2.04). A trend showed increased SLHD with each consecutive age group although a reduction in performance was identified in the U13s (d=0.50-0.59). High volumes of accumulated soccer participation in the U18s may lead to altered landing strategies indicative of high injury risk. A temporary reduction in hop performance in the U13s may also be linked to a period of adolescent awkwardness.


#3 Case study: sleep and injury in elite soccer. A mixed method approach
Reference: J Strength Cond Res. 2017 Sep 11. doi: 10.1519/JSC.0000000000002251. [Epub ahead of print]
Authors: Nedelec M, Leduc C, Dawson B, Guilhem G, Dupont G.
Summary: The present case study allowed an examination of the link between sleep and injury occurrence in an elite male soccer player competing in French League 1 and Union of European Football Associations matches. During 4 months, a mixed method approach was used, combining actigraphic sleep assessment with qualitative interviews on a daily basis. Three injuries were reported over the study period. Sleep onset latency, both in the single night (117±43 min) and in the week (78±50 min) before injury occurrence, was longer than pre-season baseline values (18±13 min; effect size (ES): 3.1 and 1.6, respectively). Similarly, sleep efficiency in the single night (73±7%) and the week (75±7%) before injury occurrence, was lower than baseline (90±3%; ES: 3.2 and 2.8, respectively). In the present case-study, sleep onset latency and efficiency were altered on the night and in the week before injury occurrence. Individualized assessment of sleep during congested playing schedules may be useful to aid in preventing injury occurrence.


#4 A comparison of isomaltulose versus maltodextrin ingestion during soccer-specific exercise
Reference: Eur J Appl Physiol. 2017 Sep 19. doi: 10.1007/s00421-017-3719-5. [Epub ahead of print]
Authors: Stevenson EJ, Watson A, Theis S, Holz A, Harper LD, Russell M
Summary: The performance and physiological effects of isomaltulose and maltodextrin consumed intermittently during prolonged soccer-specific exercise were investigated. University soccer players (n = 22) performed 120 min of intermittent exercise while consuming 8% carbohydrate-electrolyte drinks (equivalent to ~ 20 g h-1) containing maltodextrin (Glycaemic Index: 90-100), isomaltulose (Glycaemic Index: 32) or a carbohydrate-energy-free placebo in a manner replicating the practices of soccer players (i.e., during warm-up and half-time). Physical (sprinting, jumping) and technical (shooting, dribbling) performance was assessed. Blood glucose and plasma insulin (both P < 0.001) concentrations varied by trial with isomaltulose maintaining > 13% higher blood glucose concentrations between 75 and 90 min versus maltodextrin (P < 0.05). A decline in glycaemia at 60 min in maltodextrin was attenuated with isomaltulose (-19 versus -4%; P = 0.015). Carbohydrates attenuated elevations in plasma epinephrine concentrations (P < 0.05), but isomaltulose proved most effective at 90 and 120 min. Carbohydrates did not attenuate IL-6 increases or reductions in physical or technical performances (all P > 0.05). Ratings of abdominal discomfort were influenced by trial (P < 0.05) with lower values for both carbohydrates compared to PLA from 60 min onwards. Although carbohydrates (~ 20 g h-1) did not attenuate performance reductions throughout prolonged soccer-specific exercise, isomaltulose maintained higher blood glucose at 75-90 min, lessened the magnitude of the exercise-induced rebound glycaemic response and attenuated epinephrine increases whilst maintaining similar abdominal discomfort values relative to maltodextrin. When limited opportunities exist to consume carbohydrates on competition-day, low-glycaemic isomaltulose may offer an alternative nutritional strategy for exercising soccer players.


#5 The Energy Cost of Running with the Ball in Soccer
Reference: Int J Sports Med. 2017 Sep 18. doi: 10.1055/s-0043-118340. [Epub ahead of print]
Authors: Piras A, Raffi M, Atmatzidis C, Merni F, Di Michele R
Summary: Running with the ball is a soccer-specific activity frequently used by players during match play and training drills. Nevertheless, the energy cost (EC) of on-grass running with the ball has not yet been determined. The purpose of this study was therefore to assess the EC of constant-speed running with the ball, and to compare it with the EC of normal running. Eight amateur soccer players performed two 6- min runs at 10 km/h on artificial turf, respectively with and without the ball. EC was measured with indirect calorimetry and, furthermore, estimated with a method based on players' accelerations measured with a GPS receiver. The EC measured with indirect calorimetry was higher in running with the ball (4.60±0.42 J/kg/m) than in normal running (4.19±0.33 J/kg/m), with a very likely moderate difference between conditions. Instead, a likely small difference was observed between conditions for EC estimated from GPS data (4.87±0.07 vs. 4.83±0.08 J/kg/m). This study sheds light on the energy expenditure of playing soccer, providing relevant data about the EC of a typical soccer-specific activity. These findings may be a reference for coaches to precisely determine the training load in drills with the ball, such as soccer-specific circuits or small-sided games.


#6 Practical nutritional recovery strategies for elite soccer players when limited time separates repeated matches
Reference: J Int Soc Sports Nutr. 2017 Sep 12;14:35. doi: 10.1186/s12970-017-0193-8. eCollection 2017.
Authors: Ranchordas MK, Dawson JT, Russell M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5596842/pdf/12970_2017_Article_193.pdf
Summary: Specific guidelines that aim to facilitate the recovery of soccer players from the demands of training and a congested fixture schedule are lacking; especially in relation to evidence-based nutritional recommendations. The importance of repeated high level performance and injury avoidance while addressing the challenges of fixture scheduling, travel to away venues, and training commitments requires a strategic and practically feasible method of implementing specific nutritional strategies. Here we present evidence-based guidelines regarding nutritional recovery strategies within the context of soccer. An emphasis is placed on providing practically applicable guidelines for facilitation of recovery when multiple matches are played within a short period of time (i.e. 48 h). Following match-play, the restoration of liver and muscle glycogen stores (via consumption of ~1.2 g⋅kg-1⋅h-1 of carbohydrate) and augmentation of protein synthesis (via ~40 g of protein) should be prioritised in the first 20 min of recovery. Daily intakes of 6-10 g⋅kg-1 body mass of carbohydrate are recommended when limited time separates repeated matches while daily protein intakes of >1.5 g⋅kg-1 body mass should be targeted; possibly in the form of multiple smaller feedings (e.g., 6 × 20-40 g). At least 150% of the body mass lost during exercise should be consumed within 1 h and electrolytes added such that fluid losses are ameliorated. Strategic use of protein, leucine, creatine, polyphenols and omega-3 supplements could also offer practical means of enhancing post-match recovery.


#7 Risk factors for football injuries in young players aged 7 to 12 years
Reference: Scand J Med Sci Sports. 2017 Sep 18. doi: 10.1111/sms.12981. [Epub ahead of print]
Authors: Rossler R, Junge A, Chomiak J, Nemec K, Dvorak J, Lichtenstein E, Faude O
Summary: Football (soccer) is very popular amongst children. Little is known about risk factors for football injuries in children. The aim was to analyse potential injury risk factors in 7 to 12 year old players. We collected prospective data in Switzerland and the Czech Republic over two seasons. Coaches reported exposure of players (in hours), absence, and injury data via an internet-based registration system. We analysed time-to-injury data with extended Cox models accounting for correlations on team- and intra-person-level. We analysed injury risk in relation to age, sex, playing position, preferred foot, and regarding age-independent body height, body mass, and BMI. Further, we analysed injury risk in relation to playing surface. In total, 6,038 player seasons with 395,295 hours of football exposure were recorded and 417 injuries occurred. Injury risk increased by 46% (Hazard Ratio 1.46 [1.35; 1.58]; P<0.001) per year of life. Left-footed players had a higher injury risk (Hazard Ratio 1.53 [1.07; 2.19]; P=0.02) for training injuries compared to right-footed players. Injury risk was increased in age-adjusted taller players (higher percentile-rank). Higher match-training-ratios were associated with a lower risk of match injuries. Injury risk was increased on artificial turf (Rate Ratio 1.39 [1.12; 1.73]; P<0.001) and lower during indoor sessions (Rate Ratio 0.68 [0.52; 0.88]; P<0.001) compared to natural grass. Age is known as a risk factor in older players and was confirmed to be a risk factor in children's football. Playing surface and leg dominance have also been discussed previously as risk factors. Differences in injury risks in relation to sex should be investigated in the future.



American Football
#1 The Latarjet Procedure at the National Football League Scouting Combine: An Imaging and Performance Analysis
Reference: Orthop J Sports Med. 2017 Sep 1;5(9):2325967117726045. doi: 10.1177/2325967117726045. eCollection 2017 Sep.
Authors: LeBus GF, Chahla J, Sanchez G, Akamefula R, Moatshe G, Phocas A, Price MD, Whalen JM, LaPrade RF, Provencher MT
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5582664/pdf/10.1177_2325967117726045.pdf
Summary: The Latarjet procedure is commonly performed in the setting of glenoid bone loss for treatment of recurrent anterior shoulder instability; however, little is known regarding the outcomes of this procedure in elite American football players. The purpose was to (1) Determine the prevalence, clinical features, and imaging findings of elite college football athletes who present to the National Football League (NFL) Combine with a previous Latarjet procedure and (2) describe these athletes' performance in the NFL in terms of draft status and initial playing time. After review of all football players who participated in the NFL Combine from 2009 to 2016, any player with a previous Latarjet procedure was included in this study. Medical records, position on the field, and draft position were recorded for each player. In addition, imaging studies were reviewed to determine fixation type, hardware complications, and status of the bone block. For those players who were ultimately drafted, performance was assessed based on games played and started, total snaps, and percentage of eligible snaps in which the player participated during his rookie season. Overall, 13 of 2617 (<1%) players at the combine were identified with a previous Latarjet procedure. Radiographically, 8 of 13 (61%) showed 2-screw fixation, while 5 of 13 (39%) had 1 screw. Of the 13 players, 6 (46%) players demonstrated hardware complications. All players had evidence of degenerative changes on plain radiographs, with 10 (77%) graded as mild, 1 (8%) as moderate, and 2 (15%) as severe according to the Samilson Prieto classification. Six of the 13 (46%) players went undrafted, while the remaining 7 (54%) were drafted; however, no player participated in more than half of the plays for which he was eligible during his rookie season. Only a small percentage of players at the NFL Combine (<1%) had undergone a Latarjet procedure. High rates of postoperative complications and radiographically confirmed degenerative change were observed. Athletes who had undergone a Latarjet procedure demonstrated a variable amount of playing time, but none participated in more than half of their eligible plays during their rookie season.


#2 A Case Series of Pectoralis Major Injuries on One Collegiate Football Team
Reference: Curr Sports Med Rep. 2017 Sep/Oct;16(5):346-350. doi: 10.1249/JSR.0000000000000400.
Authors: Baker HP, Tjong VK, Varelas A, Wonais M, Terry MA.


#3 American football and other sports injuries may cause migraine/persistent pain decades later and can be treated successfully with electrical twitch-obtaining intramuscular stimulation (ETOIMS)
Reference: BMJ Innov. 2017 Apr;3(2):104-114. doi: 10.1136/bmjinnov-2016-000151. Epub 2017 Mar 24.
Authors: Chu J, McNally S, Bruyninckx F, Neuhauser D
Summary: Autonomous twitch elicitation at myofascial trigger points from spondylotic radiculopathies-induced denervation supersensitivity can provide favourable pain relief using electrical twitch-obtaining intramuscular stimulation (ETOIMS). The aim was to provide objective evidence that ETOIMS is safe and efficacious in migraine and persistent pain management due to decades-old injuries to head and spine from paediatric American football. An 83-year-old mildly hypertensive patient with 25-year history of refractory migraine and persistent pain self-selected to regularly receive fee-for-service ETOIMS 2/week over 20 months. He had 180 sessions of ETOIMS. Pain levels, blood pressure (BP) and heart rate/pulse were recorded before and immediately after each treatment alongside highest level of clinically elicitable twitch forces/session, session duration and intervals between treatments. Twitch force grades recorded were from 1 to 5, grade 5 twitch force being strongest. Initially, there was hypersensitivity to electrical stimulation with low stimulus parameters (500 µs pulse-width, 30 mA stimulus intensity, frequency 1.3 Hz). This resolved with gradual stimulus increments as tolerated during successive treatments. By treatment 27, autonomous twitches were noted. Spearman's correlation coefficients showed that pain levels are negatively related to twitch force, number of treatments, treatment session duration and directly related to BP and heart rate/pulse. Treatment numbers and session durations directly influence twitch force. At end of study, headaches and quality of life improved, hypertension resolved and antihypertensive medication had been discontinued. Using statistical process control methodology in an individual patient, we showed long-term safety and effectiveness of ETOIMS in simultaneous diagnosis, treatment, prognosis and prevention of migraine and persistent pain in real time obviating necessity for randomised controlled studies.


#4 Severe Exercise-Associated Hyponatremia in a Collegiate American Football Player
Reference: Curr Sports Med Rep. 2017 Sep/Oct;16(5):343-345. doi: 10.1249/JSR.0000000000000399.
Authors: Changstrom B, Brill J, Hecht S


#5 Mild Traumatic Brain Injury in a High School Football Player with Familial Hemiplegic Migraine: A Case Report
Reference: PM R. 2017 Sep 13. pii: S1934-1482(16)31114-5. doi: 10.1016/j.pmrj.2017.07.081. [Epub ahead of print]
Authors: Chand MR, Kanwar S, Peck E
Summary: Mild traumatic brain injury is a major concern in young athletes, with an estimated 1.6 to 3.8 million reported concussions in the US annually. Familial hemiplegic migraine is a rare autosomal-dominant condition characterized by sporadic episodes of transient unilateral motor weakness which may begin at any age. We present a case of a 17-year-old male with a history of familial hemiplegic migraine who suffered prolonged symptoms following a mild traumatic brain injury during sports participation.


#6 Erratum to: Editorial: Do Orthopaedic Surgeons Belong on the Sidelines at American Football Games?
Reference: Clin Orthop Relat Res. 2017 Sep 18. doi: 10.1007/s11999-017-5508-1. [Epub ahead of print]
Authors: Leopold SS, Dobbs MB, Gebhardt MC, Gioe TJ, Rimnac CM, Wongworawat MD
Summary: In the November Editorial, "Editorial: Do Orthopaedic Surgeons Belong on the Sidelines at American Football Games?" a statistic was attributed to a JAMA study (Ref. 10) that should have been attributed to an article from the New York Times (Ref. 16). The sentence in question should read: "We accept that critique, provided that the skeptics acknowledge that the best-case estimate in support of the safety of football would result in a CTE prevalence estimate of 9%, since only another 1200 ex-NFL players have died [16] since this research group [10] began studying football players' brains."


#7 Age of first exposure to American football and long-term neuropsychiatric and cognitive outcomes
Reference: Transl Psychiatry. 2017 Sep 19;7(9):e1236. doi: 10.1038/tp.2017.197.
Authors: Alosco ML, Kasimis AB, Stamm JM, Chua AS, Baugh CM, Daneshvar DH, Robbins CA, Mariani M, Hayden J, Conneely S, Au R, Torres A, McClean MD, McKee AC, Cantu RC, Mez J, Nowinski CJ, Martin BM, Chaisson CE, Tripodis Y, Stern RA
Download link: https://www.nature.com/tp/journal/v7/n9/pdf/tp2017197a.pdf
Summary: Previous research suggests that age of first exposure (AFE) to football before age 12 may have long-term clinical implications; however, this relationship has only been examined in small samples of former professional football players. We examined the association between AFE to football and behavior, mood and cognition in a large cohort of former amateur and professional football players. The sample included 214 former football players without other contact sport history. Participants completed the Brief Test of Adult Cognition by Telephone (BTACT), and self-reported measures of executive function and behavioral regulation (Behavior Rating Inventory of Executive Function-Adult Version Metacognition Index (MI), Behavioral Regulation Index (BRI)), depression (Center for Epidemiologic Studies Depression Scale (CES-D)) and apathy (Apathy Evaluation Scale (AES)). Outcomes were continuous and dichotomized as clinically impaired. AFE was dichotomized into <12 and ⩾12, and examined continuously. Multivariate mixed-effect regressions controlling for age, education and duration of play showed AFE to football before age 12 corresponded with >2 × increased odds for clinically impaired scores on all measures but BTACT: (odds ratio (OR), 95% confidence interval (CI): BRI, 2.16,1.19-3.91; MI, 2.10,1.17-3.76; CES-D, 3.08,1.65-5.76; AES, 2.39,1.32-4.32). Younger AFE predicted increased odds for clinical impairment on the AES (OR, 95% CI: 0.86, 0.76-0.97) and CES-D (OR, 95% CI: 0.85, 0.74-0.97). There was no interaction between AFE and highest level of play. Younger AFE to football, before age 12 in particular, was associated with increased odds for impairment in self-reported neuropsychiatric and executive function in 214 former American football players. Longitudinal studies will inform youth football policy and safety decisions.


#8 Cold-Water Immersion Cooling Rates in Football Linemen and Cross-Country Runners With Exercise-Induced Hyperthermia
Reference: J Athl Train. 2017 Sep 22. doi: 10.4085/1062-6050-52.7.08. [Epub ahead of print]
Authors: Godek SF, Morrison KE, Scullin G
Summary: Ideal and acceptable cooling rates in hyperthermic athletes have been established in average-sized participants. Football linemen (FBs) have a small body surface area (BSA) to mass ratio compared with smaller athletes, which hinders heat dissipation. The purpose was to determine cooling rates using cold-water immersion in hyperthermic FBs and cross-country runners (CCs). Nine FBs (age = 21.7 ± 1.7 years, height = 188.7 ± 4 cm, mass = 128.1 ± 18 kg, body fat = 28.9% ± 7.1%, lean body mass [LBM] = 86.9 ± 19 kg, BSA = 2.54 ± 0.13 m2, BSA/mass = 201 ± 21.3 cm2/kg, and BSA/LBM = 276.4 ± 19.7 cm2/kg) and 7 CCs (age = 20 ± 1.8 years, height = 176 ± 4.1 cm, mass = 68.7 ± 6.5 kg, body fat = 10.2% ± 1.6%, LBM = 61.7 ± 5.3 kg, BSA = 1.84 ± 0.1 m2, BSA/mass = 268.3 ± 11.7 cm2/kg, and BSA/LBM = 298.4 ± 11.7 cm2/kg). Participants ingested an intestinal sensor, exercised in a climatic chamber (39°C, 40% relative humidity) until either target core temperature (Tgi) was 39.5°C or volitional exhaustion was reached, and were immediately immersed in a 10°C circulated bath until Tgi declined to 37.5°C. A general linear model repeated-measures analysis of variance and independent t tests were calculated, with P < .05. Physical characteristics were different between groups. No differences existed in environmental measures or maximal Tgi (FBs = 39.12°C ± 0.39°C, CCs = 39.38°C ± 0.19°C; P = .12). Cooling times required to reach 37.5°C (FBs = 11.4 ± 4 minutes, CCs = 7.7 ± 0.06 minutes; P < .002) and therefore cooling rates (FBs = 0.156°C ± 0.06°C·min-1, CCs = .255°C ± 0.05°C·min-1; P < .002) were different. Strong correlations were found between cooling rate and body mass (r = -0.76, P < .001), total BSA (r = -0.74, P < .001), BSA/mass (r = 0.73, P < .001), LBM/mass (r = 0.72, P < .002), and LBM (r = -0.72, P < .002). Using cold-water immersion, the cooling rate in CCs (0.255°C·min-1) was greater than in FBs (0.156°C·min-1); however, both were considered ideal (≥0.155°C·min-1). Athletic trainers should realize that it likely takes considerably longer to cool large hyperthermic American-football players (>11 minutes) than smaller, leaner athletes (7.7 minutes). Cooling rates varied widely from 0.332°C·min-1 in a small runner to only 0.101°C·min-1 in a lineman, supporting the use of rectal temperature for monitoring during cooling.


#9 Head impact exposure measured in a single youth football team during practice drills
Reference: J Neurosurg Pediatr. 2017 Sep 12:1-9. doi: 10.3171/2017.5.PEDS16627. [Epub ahead of print]
Authors: Kelley ME, Kane JM, Espeland MA, Miller LE, Powers AK, Stitzel JD, Urban JE
Summary: This study evaluated the frequency, magnitude, and location of head impacts in practice drills within a youth football team to determine how head impact exposure varies among different types of drills. On-field head impact data were collected from athletes participating in a youth football team for a single season. Each athlete wore a helmet instrumented with a Head Impact Telemetry (HIT) System head acceleration measurement device during all preseason, regular season, and playoff practices. Video was recorded for all practices, and video analysis was performed to verify head impacts and assign each head impact to a specific drill. Eleven drills were identified: dummy/sled tackling, install, special teams, Oklahoma, one-on-one, open-field tackling, passing, position skill work, multiplayer tackle, scrimmage, and tackling drill stations. Generalized linear models were fitted to log-transformed data, and Wald tests were used to assess differences in head accelerations and impact rates. A total of 2125 impacts were measured during 30 contact practices in 9 athletes (mean age 11.1 ± 0.6 years, mean mass 44.9 ± 4.1 kg). Open-field tackling had the highest median and 95th percentile linear accelerations (24.7 g and 97.8 g, respectively) and resulted in significantly higher mean head accelerations than several other drills. The multiplayer tackle drill resulted in the highest head impact frequency, with an average of 0.59 impacts per minute per athlete, but the lowest 95th percentile linear accelerations of all drills. The front of the head was the most common impact location for all drills except dummy/sled tackling. Head impact exposure varies significantly in youth football practice drills, with several drills exposing athletes to high-magnitude and/or high-frequency head impacts. These data suggest that further study of practice drills is an important step in developing evidence-based recommendations for modifying or eliminating certain high-intensity drills to reduce head impact exposure and injury risk for all levels of play.

Wed

27

Sep

2017

Football is...(#16)

Straight-line sprinting might be rarely performed – however, the ones that are done might be important ones!

Wed

27

Sep

2017

Football is...(#15)

If you use SSG as a conditioning tool - Be aware of the goalkeeper!!!

Tue

26

Sep

2017

Latest research in football - week 37 - 2017

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Strategies for injury prevention in Brazilian football: Perceptions of physiotherapists and practices of premier league teams
Reference: Phys Ther Sport. 2017 Jul 25;28:1-8. doi: 10.1016/j.ptsp.2017.07.004. [Epub ahead of print]
Authors: Meurer MC, Silva MF, Baroni BM
Summary: The purpose was to describe the physiotherapists perceptions and the current practices for injury prevention in elite football (soccer) clubs in Brazil. 16 of the 20 football clubs involved in the Brazilian premier league 2015 were involved in this study. Most physiotherapists (∼88%) were active in design, testing and application of prevention programs. Previous injury, muscle imbalance, fatigue, hydration, fitness, diet, sleep/rest and age were considered "very important" or "important" injury risk factors by all respondents. The methods most commonly used to detect athletes' injury risk were: monitoring of biochemical markers (100% of teams), isokinetic dynamometry (81%), questionnaires (75%), functional movement screen (56%), fleximetry (56%) and horizontal jump tests (50%). All clubs used strength training, functional training, core exercises and balance/proprioception exercises in their injury prevention program; and Nordic hamstring exercise and other eccentric exercises were used by 94% of clubs. "FIFA 11+" prevention program was adapted by 88% of clubs. Physiotherapists perceptions and current practices of injury prevention within Brazilian elite football clubs were similar to those employed in developed countries. There remains a gap between clinical practice and scientific evidence in high performance football.


#2 Prevention of Head and Brain Injuries in Football: Is there a Need to Ban Headings?
Reference: Sportverletz Sportschaden. 2017 Sep;31(3):143-153. doi: 10.1055/s-0043-113208. Epub 2017 Sep 4. [Article in German; Abstract available in German from the publisher]
Authors: Krutsch V, Krutsch W, Jansen P, Hoffmann H, Angele P, Lehmann J, Loose O, Gansslen A, Nerlich M, Weber J.
Summary: Football, the most popular sports worldwide, is associated with a high number of injuries. Head and brain injuries in football are less frequent, but may result in severe long-term damage. The mechanisms of these injuries in football are multifactorial, and the ball is rarely the main cause of a head injury. Short-term, medium-term and long-term consequences of headings in football are insufficiently examined, and there are hardly any case reports about severe episodes. Heading has been banned in US junior football since November 2015, which is understandable considering the higher risk for head injuries in popular American sports such as ice hockey or American football and people's fear associated with this risk. However, the decision to ban heading in football is not based on scientific results, and different experiences have been made in European football. Therefore, this decision should not simply be transferred to Europe. In fact, other injury prevention strategies for head injuries in junior football are necessary, such as the adaptation of ball sizes, which has already been implemented. It is not necessary to change match rules in the form of a general ban on heading in football. Further scientific studies are needed for standardisation in football worldwide.


#3 Does player unavailability affect football teams' match physical outputs? A two-season study of the UEFA champions league
Reference: J Sci Med Sport. 2017 Aug 24. pii: S1440-2440(17)30995-7. doi: 10.1016/j.jsams.2017.08.007. [Epub ahead of print]
Authors: Windt J, Ekstrand J, Khan KM, McCall A, Zumbo BD
Summary: Player unavailability negatively affects team performance in elite football. However, whether player unavailability and its concomitant performance decrement is mediated by any changes in teams' match physical outputs is unknown. We examined whether the number of players injured (i.e. unavailable for match selection) was associated with any changes in teams' physical outputs. Between-team variation was calculated by correlating average team availability with average physical outputs. Within-team variation was quantified using linear mixed modelling, using physical outputs - total distance, sprint count (efforts over 20km/h), and percent of distance covered at high speeds (>14km/h) - as outcome variables, and player unavailability as the independent variable of interest. To control for other factors that may influence match physical outputs, stage (group stage/knockout), venue (home/away), score differential, ball possession (%), team ranking (UEFA Club Coefficient), and average team age were all included as covariates. Teams' average player unavailability was positively associated with the average number of sprints they performed in matches across two seasons. Multilevel models similarly demonstrated that having 4 unavailable players was associated with 20.8 more sprints during matches in 2015/2016, and with an estimated 0.60-0.77% increase in the proportion of total distance run above 14km/h in both seasons. Player unavailability had a possibly positive and likely positive association with total match distances in the two respective seasons. Having more players injured and unavailable for match selection was associated with an increase in teams' match physical outputs.


#4 Hypernetworks Reveal Compound Variables That Capture Cooperative and Competitive Interactions in a Soccer Match
Reference: Front Psychol. 2017 Aug 28;8:1379. doi: 10.3389/fpsyg.2017.01379. eCollection 2017.
Authors: Ramos J, Lopes RJ, Marques P, Araujo D
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5581353/pdf/fpsyg-08-01379.pdf
Summary: The combination of sports sciences theorization and social networks analysis (SNA) has offered useful new insights for addressing team behavior. However, SNA typically represents the dynamics of team behavior during a match in dyadic interactions and in a single cumulative snapshot. This study aims to overcome these limitations by using hypernetworks to describe illustrative cases of team behavior dynamics at various other levels of analyses. Hypernetworks simultaneously access cooperative and competitive interactions between teammates and opponents across space and time during a match. Moreover, hypernetworks are not limited to dyadic relations, which are typically represented by edges in other types of networks. In a hypernetwork, n-ary relations (with n > 2) and their properties are represented with hyperedges connecting more than two players simultaneously (the so-called simplex-plural, simplices). Simplices can capture the interactions of sets of players that may include an arbitrary number of teammates and opponents. In this qualitative study, we first used the mathematical formalisms of hypernetworks to represent a multilevel team behavior dynamics, including micro (interactions between players), meso (dynamics of a given critical event, e.g., an attack interaction), and macro (interactions between sets of players) levels. Second, we investigated different features that could potentially explain the occurrence of critical events, such as, aggregation or disaggregation of simplices relative to goal proximity. Finally, we applied hypernetworks analysis to soccer games from the English premier league (season 2010-2011) by using two-dimensional player displacement coordinates obtained with a multiple-camera match analysis system provided by STATS (formerly Prozone). Our results show that (i) at micro level the most frequently occurring simplices configuration is 1vs.1 (one attacker vs. one defender); (ii) at meso level, the dynamics of simplices transformations near the goal depends on significant changes in the players' speed and direction; (iii) at macro level, simplices are connected to one another, forming "simplices of simplices" including the goalkeeper and the goal. These results validate qualitatively that hypernetworks and related compound variables can capture and be used in the analysis of the cooperative and competitive interactions between players and sets of players in soccer matches.


#5 Monitoring training load and fatigue in soccer players with physiological markers
Reference: Physiol Behav. 2017 Sep 5. pii: S0031-9384(17)30278-0. doi: 10.1016/j.physbeh.2017.09.004. [Epub ahead of print]
Authors: Djaoui L, Haddad M, Chamari K, Dellal A
Summary: The quantification and monitoring of training load (TL) has been the topic of many scientific works in the last fifteen years. TL monitoring helps coaches to individually prescribe, follow-up, analyse, adjust and programme training sessions. In particular, the aim of the present review was to provide a critical literature report regarding different physiological markers of TL monitoring, particularly in soccer, as the load is specific to individual sports. Therefore, the interests and limitations of heart rate (HR), HR variability (HRV) and biochemical variables (blood, urinary and hormonal variations) were analysed, with a special focus on daily measures (before, during and after training) and monitoring throughout a whole season. It appears that the most relevant markers were the resting HR before training, HR reserve during training, HRV during rest days, blood lactate, and blood and salivary immunological status in follow-ups throughout the season. Urinary markers indicative of the players' hydration status also deserve attention. However, these objective markers should be considered with a subjective marker of TL such as the rating of perceived exertion to give a more precise quantification of TL and its perception. Future research could be directed towards urinary marker analysis and the analysis of specific markers of TL, which could be related to injury occurrence and to performance during competition.


#6 Perception, Action, and Cognition of Football Referees in Extreme Temperatures: Impact on Decision Performance
Reference: Front Psychol. 2017 Aug 29;8:1479. doi: 10.3389/fpsyg.2017.01479. eCollection 2017.
Authors: Gaoua N, de Oliveira RF, Hunter S
Summary: Different professional domains require high levels of physical performance alongside fast and accurate decision-making. Construction workers, police officers, firefighters, elite sports men and women, the military and emergency medical professionals are often exposed to hostile environments with limited options for behavioral coping strategies. In this (mini) review we use football refereeing as an example to discuss the combined effect of intense physical activity and extreme temperatures on decision-making and suggest an explicative model. In professional football competitions can be played in temperatures ranging from -5°C in Norway to 30°C in Spain for example. Despite these conditions, the referee's responsibility is to consistently apply the laws fairly and uniformly, and to ensure the rules are followed without waning or adversely influencing the competitiveness of the play. However, strenuous exercise in extreme environments imposes increased physiological and psychological stress that can affect decision-making. Therefore, the physical exertion required to follow the game and the thermal strain from the extreme temperatures may hinder the ability of referees to make fast and accurate decisions. Here, we review literature on the physical and cognitive requirements of football refereeing and how extreme temperatures may affect referees' decisions. Research suggests that both hot and cold environments have a negative impact on decision-making but data specific to decision-making is still lacking. A theoretical model of decision-making under the constraint of intense physical activity and thermal stress is suggested. Future naturalistic studies are needed to validate this model and provide clear recommendations for mitigating strategies.


#7 Trends in aggressive play and refereeing among the top five European soccer leagues
Reference: J Sports Sci. 2017 Sep 12:1-9. doi: 10.1080/02640414.2017.1377911. [Epub ahead of print]
Authors: Sapp RM, Spangenburg EE, Hagberg JM
Summary: Current trends suggest professional soccer is becoming less aggressive, with England often argued to have the most aggressive of the top European leagues. The purpose of this study was to investigate differences in fouls and cards as indicators of aggressive play in the first divisions of England, France, Germany, Italy, and Spain over the past decade. Number of fouls per match and per yellow card has decreased in all leagues since 2007/08, though attempted tackles per foul has not changed or has increased. A lack of substantial rule changes suggests players have become less aggressive in tackling as opposed to referees becoming more lenient. Total number of fouls and cards per match were consistently lower in the English Premier League, however attempted tackles per foul was higher. The data also demonstrate the notions of home advantage and potentially referee bias, since referees tended to call more fouls and award more cards to away teams. Lastly, number of attempted tackles per foul and yellow cards received exhibited the strongest correlations with final league position across the leagues. In conclusion, our data support that elite European soccer has become less aggressive and the English Premier League is the most aggressive league.


#8 Effects of repeated-sprints with changes of direction on youth soccer player's performance: Impact of initial fitness level
Reference: J Strength Cond Res. 2017 Sep 6. doi: 10.1519/JSC.0000000000002232. [Epub ahead of print]
Authors: Nakamura FY, Sanchez-Sanchez J, Ramirez-Campillo R, Petisco C, Gonzalo-Skok O, Rodriguez-Fernandez A, Minano J
Summary: The aim of this study was to assess the effect of an 8-week repeated sprint with change of direction training program on repeated sprint, intermittent endurance and change of direction performance in youth soccer players with different aerobic fitness levels. Athletes were randomly assigned into a soccer-only (n=9; age, 14.9±0.4 yr) and soccer plus repeated sprint with change of direction (RS-COD) training programs for players with high (n=10; age, 14.4±0.5 yr) and low (n=10; age, 14.4±0.5 yr) aerobic fitness. RS-COD was completed two days per week, involving three sets of ten 18-m sprints with two changes of direction of 90°. The soccer-only group achieved greater improvements in intermittent endurance (ES = 0.61) and sprint decrement during RS ability test (ES = 0.77) compared to the RS-COD groups (ES = 0.19 to 0.24; ES = -0.27 to 0.02; respectively). RS-COD training improved repeated sprint (ES = 0.16 to 0.38) and change of direction (ES = 0.48) performance in high, but not in low fitness players (ES = 0.03 to 0.13; ES = 0.16; respectively). Moreover, improvements in repeated sprint and change of direction were (possibly) greater in high compared to low fitness and soccer-only trained players (possibly to very likely). In conclusion, although RS-COD training may positively affect repeated sprint and change of direction performance, its effects may vary according to the initial aerobic fitness of youth soccer players, with trivial effect on intermittent endurance in high-aerobic fitness players and possible beneficial effect on low-aerobic fitness players.


#9 A Cross-Continental Study on Children's Drawings of Football Players: Implications for Understanding Key Issues and Controversies in Human Figure Drawings
Reference: Eur J Psychol. 2017 Aug 31;13(3):455-471. doi: 10.5964/ejop.v13i3.1237. eCollection 2017 Aug.
Authors: Baluch B, Duffy LJ, Badami R, Pereira ECA
Summary: Professionals examine various aspects of girls' and boys' drawings as a way of understanding their intelligence, personality and emotional state. However, the extent to which such measures could be universally generalised or attributed to a specific cultural norm is still a debatable issue. In the present study five key features of children's drawings namely: the size (height) of the drawings, profile or full face, figure in action or static, shaded or non-shaded and the nature of additional details were examined from a cross-cultural perspective, and by providing a topic (football) for which children's drawing of a human figure could provide opportunities for the latter indices to manifest and flourish. Children from three countries; England, Iran and Brazil, representing three continents took part in this study. The participants were asked to draw a football player from their own country and from the other participating countries. The results showed that Brazilian children differ from Iranian and English children by drawing significantly smaller figures and putting more football action in the drawings. Shading of the figure drawn was more prevalent amongst English children. Such findings have implications for the interpretation of key aspects of children's drawings in educational, clinical and therapeutic settings and from a universal vs. culturally-specific viewpoint.


American Football
#1 What is the Value of a National Football League Draft Pick? An Analysis Based on Changes Made in the Collective Bargaining Agreement
Reference:  J Strength Cond Res. 2017 Jun 2. doi: 10.1519/JSC.0000000000002045. [Epub ahead of print]
Authors: Kraeutler MJ, Carver TJ, Belk JW, McCarty EC
Summary: The purpose of this study was to analyze and compare the value of players drafted in early rounds of the NFL Draft since the new collective bargaining agreement (CBA) began in 2011. The NFL's player statistics database and database of player contract details were searched for players drafted in the first three rounds of the 2011 to 2013 NFL Drafts. Performance outcomes specific to each position were divided by each player's salary to calculate a value statistic. Various demographics, NFL Combine results, and total number of games missed due to injury were also recorded for each player. These statistics were compared within each position between players selected in the 1st round of the NFL Draft (Group A) versus those drafted in the 2nd or 3rd round (Group B). A total of 147 players were included (Group A 35, Group B 112). Overall, players in Group A were significantly taller (p < 0.01) and heavier (p = 0.037) than players in Group B. Group B demonstrated significantly greater value statistics than Group A for quarterbacks (p = 0.028), wide receivers (p < 0.001), defensive tackles (p = 0.019), and cornerbacks (p < 0.001). No significant differences were found between groups with regard to number of games missed due to injury. Players drafted in the 2nd or 3rd rounds of the NFL Draft often carry more value than those drafted in the 1st round. NFL teams may wish to more frequently trade down in the Draft rather than trading up.


#2 Nano-Composite Foam Sensor System in Football Helmets
Reference: Ann Biomed Eng. 2017 Sep 7. doi: 10.1007/s10439-017-1910-9. [Epub ahead of print]
Authors: Merrell AJ, Christensen WF, Seeley MK, Bowden AE, Fullwood DT
Summary: American football has both the highest rate of concussion incidences as well as the highest number of concussions of all contact sports due to both the number of athletes and nature of the sport. Recent research has linked concussions with long term health complications such as chronic traumatic encephalopathy and early onset Alzheimer's. Understanding the mechanical characteristics of concussive impacts is critical to help protect athletes from these debilitating diseases and is now possible using helmet-based sensor systems. To date, real time on-field measurement of head impacts has been almost exclusively measured by devices that rely on accelerometers or gyroscopes attached to the player's helmet, or embedded in a mouth guard. These systems monitor motion of the head or helmet, but do not directly measure impact energy. This paper evaluates the accuracy of a novel, multifunctional foam-based sensor that replaces a portion of the helmet foam to measure impact. All modified helmets were tested using a National Operating Committee Standards for Athletic Equipment-style drop tower with a total of 24 drop tests (4 locations with 6 impact energies). The impacts were evaluated using a headform, instrumented with a tri-axial accelerometer, mounted to a Hybrid III neck assembly. The resultant accelerations were evaluated for both the peak acceleration and the severity indices. These data were then compared to the voltage response from multiple Nano Composite Foam sensors located throughout the helmet. The foam sensor system proved to be accurate in measuring both the HIC and Gadd severity index, as well as peak acceleration while also providing additional details that were previously difficult to obtain, such as impact energy.


#3 Examining Play Counts and Measurements of Injury Incidence in Youth Football
Reference: J Athl Train. 2017 Sep 7. doi: 10.4085/1062-6050-52.7.06. [Epub ahead of print]
Authors: Kerr ZY, Yeargin SW, Djoko A, Dalton SL, Niceley MM, Dompier TP
Summary: Whereas researchers have provided estimates for the number of head impacts sustained within a youth football season, less is known about the number of plays across which such impact exposure occurs.  The objective was to estimate the number of plays in which youth football players participated during the 2013 season and to estimate injury incidence through play-based injury rates. Youth football players (N = 2098; age range, 5-15 years) from 105 teams in 12 recreational leagues across 6 states participated in this study.  We calculated the average number of athlete-plays per season and per game using independent-samples t tests to compare age groups (5-10 years old versus 11-15 years old) and squad sizes (<20 versus ≥20 players); game injury rates per 1000 AE and per 10 000 athlete-plays; and injury rate ratios (IRRs) with 95% confidence intervals (CIs) to compare age groups. On average, youth football players played 333.9 ± 178.5 plays per season and 43.9 ± 24.0 plays per game. Age groups (5- to 10-year-olds versus 11- to 15-year-olds) did not differ in the average number of plays per season (335.8 versus 332.3, respectively; t2086.4 = 0.45, P = .65) and per game (44.1 versus 43.7, respectively; t2092.3 = 0.38, P = .71). However, players from smaller teams participated in more plays per season (373.7 versus 308.0; t1611.4 = 8.15, P < .001) and per game (47.7 versus 41.4; t1523.5 = 5.67, P < .001). Older players had a greater game injury rate than younger players when injury rates were calculated per 1000 AEs (23.03 versus 17.86/1000 AEs; IRR = 1.29; 95% CI = 1.04, 1.60) or per 10 000 athlete- plays (5.30 versus 4.18/10 000 athlete-plays; IRR = 1.27; 95% CI = 1.02, 1.57). A larger squad size was associated with a lower average number of plays per season and per game. Increasing youth football squad sizes may help reduce head-impact exposure for individual players. The AE-based injury rates yielded effect estimates similar to those of play-based injury rates.


#4 Editorial: Do Orthopaedic Surgeons Belong on the Sidelines at American Football Games?
Reference: Clin Orthop Relat Res. 2017 Sep 5. doi: 10.1007/s11999-017-5483-6. [Epub ahead of print]
Authors: Leopold SS, Dobbs MB, Gebhardt MC, Gioe TJ, Rimnac CM, Wongworawat MD
Download link: https://link.springer.com/content/pdf/10.1007%2Fs11999-017-5483-6.pdf



Australian Football
#1 Australian Football League concussion guidelines: what do community players think?
Reference: BMJ Open Sport Exerc Med. 2016 Nov 28;2(1):e000169. doi: 10.1136/bmjsem-2016-000169. eCollection 2016.
Authors: White PE, Donaldson A, Sullivan SJ, Newton J, Finch CF
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5566260/pdf/bmjsem-2016-000169.pdf
Summary: Preventing concussion in sport is a global challenge. To assess community-level adult male Australian Football players' views on following the Australian Football League's (AFL) concussion guidelines. 3 focus groups, each comprising 6 players from 1 regional league, were conducted until saturation of issues raised. Discussions followed a semistructured script and were audio-recorded and transcribed verbatim. Thematic analysis was conducted by 2 coders independently. Identified advantages of the guidelines included highlighting the seriousness of concussion; changing the culture around playing with concussion and shifting return-to-play decision responsibility from players to others. Disadvantages included players being removed from play unnecessarily; removal of players' rights to decide if they are fit to play and players changing their behaviours to avoid being removed from play. Identified facilitators to guideline use included local league enforcement; broad information dissemination and impartial medically trained staff to assess concussion. Identified barriers to guideline use included players' desire to play at all costs; external pressure that encouraged players to return to play prematurely; and inconvenience and cost. Players generally understand that the AFL concussion guidelines protect their long-term welfare. However, their desire to play at all costs and help their team win is a common barrier to reporting concussion and adhering to guidelines. Leagues should take a lead role by mandating and enforcing the use of the guidelines and educating coaches, game day medical providers and players. The return-to-play component of the guidelines is complex and needs further consideration in the context of community sport.


#2 Effect of Prior Injury on Changes to Biceps Femoris Architecture across an Australian Football League Season
Reference: Med Sci Sports Exerc. 2017 Oct;49(10):2102-2109. doi: 10.1249/MSS.0000000000001333.
Authors: Timmins RG, Bourne MN, Hickey JT, Maniar N, Tofari PJ, Williams MD, Opar DA
Summary: The purpose was to assess in-season alterations of biceps femoris long head (BFlh) fascicle length in elite Australian footballers with and without a history of unilateral hamstring strain injury (HSI) in the past 12 months. Thirty elite Australian football players were recruited. Twelve had a history of unilateral HSI. Eighteen had no HSI history. All had their BFlh architecture assessed at approximately monthly intervals, six times across a competitive season. The previously injured limb's BFlh fascicles increased from the start of the season and peaked at week 5. Fascicle length gradually decreased until the end of the season, where they were shortest. The contralateral uninjured limb's fascicles were the longest when assessed at week 5 and showed a reduction in-season where weeks 17 and 23 were shorter than week 1. Control group fascicles were longest at week 5 and reduced in-season. The previously injured limb's BFlh fascicles were shorter than the control group at all weeks and the contralateral uninjured limb at week 5. Compared with the control group, the contralateral uninjured limb had shorter fascicles from weeks 9 to 23. Athletes with a history of HSI end the season with shorter fascicles than they start. Limbs without a history of HSI display similar BFlh fascicle lengths at the end of the season as they begin with. All athletes increase fascicle length at the beginning of the season; however, the extent of the increase differed based on history of HSI. These findings show that a HSI history may influence structural adaptation of the BFlh in-season.


#3 The validity and reliability of the sphygmomanometer for hip strength assessment in Australian football players
Reference: Physiother Theory Pract. 2017 Sep 11:1-6. doi: 10.1080/09593985.2017.1374492. [Epub ahead of print]
Authors: Toohey LA, de Noronha M, Taylor C, Thomas J
Summary: The purpose was to investigate the intra-rater and inter-rater reliability of the sphygmomanometer for the assessment of the adductor squeeze test and isometric hip abduction strength and to investigate the concurrent validity of the sphygmomanometer for the assessment of hip muscular strength. Thirty-two healthy adult male community Australian football players (age 23.9 ± 4.5 years) were assessed by two blinded raters that measured the strength of the adductor squeeze test and isometric hip abduction, using a commercially available sphygmomanometer. Concurrent validity was calculated using handheld dynamometry as the reference standard. Moderate to high intra-rater reliability (ICC = 0.61 to 0.92) and high inter-rater reliability (ICC = 0.77 to 0.91) were found. High concurrent validity (Pearson's r = 0.77 to 0.91) was established. Sixteen of the participants reached the maximal reading of the sphygmomanometer, demonstrating a ceiling effect. A sphygmomanometer is a cost-efficient device that appears to be both reliable and valid for the assessment of hip strength, offering clinicians an alternate and easily accessible option to obtain objective strength data. A ceiling effect may limit the application of the sphygmomanometer as a strength measurement device in stronger individuals.

Tue

26

Sep

2017

Football is...(#14)

There are various high-speed variations that a footballer needs to perform during the game.

Fri

22

Sep

2017

Football is...(#13)

Control the ball - control the game

Thu

21

Sep

2017

Football is...(#12)

Running laps is good for footballers…unless you know SSG?

Thu

21

Sep

2017

Latest research in football - week 36 - 2017

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Bone Turnover Markers and Lean Mass in Pubescent Boys: Comparison Between Elite Soccer Players and Controls
Reference: Pediatr Exerc Sci. 2017 Sep 5:1-20. doi: 10.1123/pes.2017-0090. [Epub ahead of print]
Authors: Nebigh A, Abed ME, Borji R, Sahli S, Sellami S, Tabka Z, Rebai H
Summary: The aim of this study was to examine the relationship between bone mass and bone turnover markers with lean mass in pubescent soccer players. Two groups participated in this study 65 elite young soccer players that trained from 6 to 8 hours per week and 60 controls. Bone mineral density (BMD), bone mineral content (BMC) in the whole body, lower limbs, lumbar spine, and femoral neck, biochemical markers of osteocalcin (OC), bone-specific alkaline phosphatase (BAP), C-telopeptide type I collagen (CTX) and total lean mass were assessed. Young soccer players showed higher BMD and BMC in the whole body and weight-bearing sites (p<0.001). Indeed, total lean mass correlated with whole body BMD and BMC (p<0.001). There were significant differences within the bone formation markers and OC (formation) / CTX (resorption) ratio between young soccer players compared to the control group; but no significant difference in (CTX) between the two groups was observed. The study showed a significant positive correlation between (BAP), (OC) and total lean mass (r = 0.29; r = 0.31; p<0.05, respectively) only for the young soccer players. Findings of this study highlight the importance of soccer practice for bone mineral parameters and bone turnover markers during the puberty stage.


#2 Neuromuscular Responses to Conditioned Soccer Sessions Assessed Via GPS-Embedded Accelerometers: Insights Into Tactical Periodization
Reference: Int J Sports Physiol Perform. 2017 Sep 5:1-21. doi: 10.1123/ijspp.2017-0045. [Epub ahead of print]
Authors: Buchheit M, Lacome M, Cholley Y, Simpson BM
Summary: The purpose was to 1) examine the reliability of field-based running-specific measures of neuromuscular function assessed via GPS-embedded accelerometers and 2) examine their responses to three typical conditioned sessions (i.e., Strength, Endurance and Speed) in elite soccer players. Before and immediately after each session, vertical jump (CMJ) and adductors squeeze strength (Groin) performances were recorded. Players also performed a 4-min run at 12 km/h followed by 4 ~60-m runs (run =12 s, r =33 s). GPS (15-Hz) and accelerometer (100 Hz) data collected during the four runs + the recovery periods excluding the last recovery period were used to derive vertical stiffness (K), peak loading force (peak force over all the foot-strikes, Fpeak) and propulsion efficiency (i.e., ratio between velocity and force loads, Vl/Fl). Typical errors were small (CMJ, Groin, K and Vl/Fl) and moderate (Fpeak), with moderate (Fpeak), high (K and Vl/Fl) and very high ICC (CMJ and Groin). After all sessions, there were small decreases in Groin and increases in K, while changes in F were all unclear. In contrast, the CMJ and Vl/Fl ratio responses were session-dependent: small increase in CMJ after Speed and Endurance, but unclear changes after Strength; the Vl/Fl ratio increased largely after Strength, while there was a small and a moderate decrease after the Endurance and Speed, respectively. Running-specific measures of neuromuscular function assessed in the field via GPS-embedded accelerometers show acceptable levels of reliability. While the three sessions examined may be associated with limited neuromuscular fatigue, changes in neuromuscular performance and propulsion-efficiency are likely session objective-dependent.


#3 How Game Location Affects Soccer Performance: T-Pattern Analysis of Attack Actions in Home and Away Matches
Reference: Front Psychol. 2017 Aug 21;8:1415. doi: 10.3389/fpsyg.2017.01415. eCollection 2017.
Authors: Diana B, Zurloni V, Elia M, Cavalera CM, Jonsson GK, Anguera MT
Download link: http://journal.frontiersin.org/article/10.3389/fpsyg.2017.01415/full
Summary: The influence of game location on performance has been widely examined in sport contexts. Concerning soccer, game-location affects positively the secondary and tertiary level of performance; however, there are fewer evidences about its effect on game structure (primary level of performance). This study aimed to detect the effect of game location on a primary level of performance in soccer. In particular, the objective was to reveal the hidden structures underlying the attack actions, in both home and away matches played by a top club (Serie A 2012/2013-First Leg). The methodological approach was based on systematic observation, supported by digital recordings and T-pattern analysis. Data were analyzed with THEME 6.0 software. A quantitative analysis, with nonparametric Mann-Whitney test and descriptive statistics, was carried out to test the hypotheses. A qualitative analysis on complex patterns was performed to get in-depth information on the game structure. This study showed that game tactics were significantly different, with home matches characterized by a more structured and varied game than away matches. In particular, a higher number of different patterns, with a higher level of complexity and including more unique behaviors was detected in home matches than in the away ones. No significant differences were found in the number of events coded per game between the two conditions. THEME software, and the corresponding T-pattern detection algorithm, enhance research opportunities by going further than frequency-based analyses, making this method an effective tool in supporting sport performance analysis and training.


#4 Prevalence of FAI radiographic hip abnormalities in elite soccer players: are there differences related to skeletal maturity?
Reference: BMJ Open Sport Exerc Med. 2017 Feb 21;2(1):e000162. doi: 10.1136/bmjsem-2016-000162. eCollection 2016.
Authors: Monckeberg J, Amenabar T, Rafols C, Garcia N, Yañez R
Download link: http://bmjopensem.bmj.com/content/bmjosem/2/1/e000162.full.pdf
Summary: Femoroacetabular impingement (FAI) can be a source of hip pain in young adults. Some reports have revealed that participation in high-impact sports may play a role in the development of cam deformity, and there is a higher prevalence of signs of cam impingement in asymptomatic adolescents who participate in soccer and basketball than in non-athlete controls; however, current evidence is scarce regarding the initiation and development of deformities. The aim of this study was to evaluate the prevalence of radiographic hip abnormalities related to FAI in young elite soccer players and compare this with findings in a group of adult elite soccer players. Anteroposterior pelvic and cross-table hip radiographs were obtained for 75 young elite soccer players with skeletal immaturity (group 1) and for 75 adult elite soccer players (group 2), all of whom were previously asymptomatic and had no history of hip disease. After exclusion, group 1 included 72 patients, and group 2 included 70 patients. Radiological signs of FAI were evaluated. 34 subjects in groups 1 and 2 demonstrated cam morphology. The prevalence of pincer morphology was 30 in group 1 and 36 in group 2. However, these differences were not statistically significant. We found no differences in the prevalence of FAI radiological signs between soccer players in their late adolescence and adult soccer players.


#5 Comparison of physical activities of female football players in junior high school and high school
Reference: J Phys Ther Sci. 2017 Aug;29(8):1352-1356. doi: 10.1589/jpts.29.1352. Epub 2017 Aug 10.
Authors: Inoue Y, Otani Y, Takemasa S
Summary: This study aimed to compare physical activities between junior high school and high school female football players in order to explain the factors that predispose to a higher incidence of sports injuries in high school female football players. Twenty-nine female football players participated. Finger floor distance, the center of pressure during single limb stance with eyes open and closed, the 40-m linear sprint time, hip abduction and extension muscle strength and isokinetic knee flexion and extension peak torque were measured. The modified Star Excursion Balance Test, the three-steps bounding test and three-steps hopping tests, agility test 1 (Step 50), agility test 2 (Forward run), curl-up test for 30 seconds and the Yo-Yo intermittent recovery test were performed. The high school group was only significantly faster than the junior high school group in the 40-m linear sprint time and in the agility tests. The distance of the bounding test in the high school group was longer than that in the junior high school group. Agility and speed increase with growth; however, muscle strength and balance do not develop alongside. This unbalanced development may cause a higher incidence of sports injuries in high school football players.


#6 Descriptive analysis of objectively assessed physical activity among talented soccer players: a study of three Norwegian professional football clubs
Reference: BMJ Open Sport Exerc Med. 2017 Feb 21;2(1):e000178. doi: 10.1136/bmjsem-2016-000178. eCollection 2016.
Authors: Saether SA, Aspvik NP
Download link: http://bmjopensem.bmj.com/content/bmjosem/2/1/e000178.full.pdf
Summary: Talented football players are expected to overcome large training and match loads, indicating a high weekly level of physical activity (PA). With the use of accelerometers, the aim of this study was to objectively describe the players' total time spent in moderate-to-vigorous PA (MVPA), vigorous PA (VPA) and very vigorous PA (VVPA) per day in 1 week. Since high-intensity PA has been highlighted as important in terms of overall PA load, we also included 2 and 4 min bouts of VPA. Data were collected in three junior teams in professional football clubs in March (club 1: 2014, club 2: 2012 and club 3: 2011). A one-way analysis of variance was applied to analyse differences between the three respective clubs. The players averaged 77.2-86.2 min in MVPA, 14.9-18.5 min in VPA and 1.0-3.1 in VVPA per day. While there were no differences in total time spent in MVPA and VPA per day, VVPA was significantly higher in club 1 (p<0.01) compared with clubs 2 and 3. Moreover, when using the VPA bouts, club 3 (p<0.01) achieved significantly more time in this intensity compared with clubs 1 and 2. This study acknowledges the importance of including both club-related and non-club-related PA when analysing talented football players' PA level. We suggest that future studies examining players' PA with accelerometers should emphasise time spent in high-intensity PA and how this is associated with physical overload, psychological burnout and risk of injury.


#7 Cryotherapy Re-Invented: Application of Phase Change Material for Recovery in Elite Soccer
Reference: Int J Sports Physiol Perform. 2017 Sep 5:1-21. doi: 10.1123/ijspp.2017-0334. [Epub ahead of print]
Authors: Clifford T, Abbott W, Kwiecien SY, Howatson G, McHugh MP
Summary: This study examined whether donning lower body garments fitted with cooled phase change material (PCM) would enhance recovery after a soccer match. In a randomized, crossover design, eleven elite-soccer players from the reserve squad of a team in the 2nd highest league in England wore PCM cooled to 15°C (PCMcold) or left at ambient temperature (PCMamb; sham control) for 3 h after a soccer match. To assess recovery, countermovement jump (CMJ) height, maximal isometric voluntary contraction (MIVC), muscle soreness (MS), and the adapted Brief Assessment of Mood Questionnaire (BAM+) were measured before, 12, 36 and 60 h after each match. Pre and post intervention, a belief questionnaire (BFQ) was completed to determine perceived effectiveness of each garment. Results are comparisons between the two conditions at each time point post-match. MIVC at 36 h post was greater with PCMcold vs. PCMwarm (P =0.005; ES=1.59; 95% CI=3.9 to 17.1%). MIVC also tended to be higher at 60 h post (P =0.051; ES=0.85; 95% CI= -0.4 to 11.1%). MS was 26.5% lower in PCMcold vs. PCMwarm at 36 h (P =0.02; ES=1.7; 95% CI= -50.4 mm to -16.1 mm) and 24.3% lower at 60 h (P =0.039; ES=1.1; 95% CI= -26.9 mm to -0.874 mm). There were no between condition differences in post-match CMJ height or BAM+ (P >0.05). The BFQ revealed that players felt the PCMcold was more effective than the PCMamb after the intervention (P =0.004). PCM cooling garments provide a practical means of delivering prolonged post-exercise cooling and thereby accelerating recovery in elite soccer players.


#8 Adding Fish Oil to Whey Protein, Leucine and Carbohydrate Over a 6 Week Supplementation Period Attenuates Muscle Soreness Following Eccentric Exercise in Competitive Soccer Players
Reference: Int J Sport Nutr Exerc Metab. 2017 Sep 5:1-28. doi: 10.1123/ijsnem.2017-0161. [Epub ahead of print]
Authors: Philpott JD, Donnelly C, Walshe IH, Dick J, Galloway SDR, Tipton KD, Witard OC
Summary: Soccer players often experience eccentric exercise-induced muscle damage given the physical demands of soccer match-play. Since long chain n-3 polyunsaturated fatty acids (n-3PUFA) enhance muscle sensitivity to protein supplementation, dietary supplementation with a combination of fish oil-derived n-3PUFA, protein and carbohydrate may promote exercise recovery. This study examined the influence of adding n-3PUFA to a whey protein, leucine and carbohydrate containing beverage over a 6 week supplementation period on physiological markers of recovery measured over 3 days following eccentric exercise. Competitive soccer players were assigned to one of three conditions (2 × 200mL): FO (n=10) contained n-3PUFA (1100mg DHA/EPA - approx. 550mg DHA, 550mg EPA), whey protein (15g), leucine (1.8g) and carbohydrate (20g); PRO (n=10) contained whey protein (15g), leucine (1.8g) and carbohydrate (20g) and CHO (n=10) contained carbohydrate (24g). Eccentric exercise consisted of unilateral knee extension/flexion contractions on both legs separately. Maximal force production was impaired by 22% during the 72 hour recovery period following eccentric exercise (p<0.05). Muscle soreness, expressed as AUC during 72 hour recovery, was less in FO (1948±1091 mm×72 h) than PRO (4640±2654 mm×72h, p<0.05) and CHO (4495±1853 mm×72h p=0.10). Blood concentrations of creatine kinase, expressed as AUC, were ~60% lower in FO compared to CHO (p<0.05) and tended to be lower (~39%, p = 0.07) than PRO. No differences in muscle function, soccer performance or blood c-reactive protein concentrations were observed between groups. In conclusion, the addition of n-3PUFA to a beverage containing whey protein, leucine and carbohydrate ameliorates the increase in muscle soreness and blood concentrations of creatine kinase following eccentric exercise in competitive soccer players.


#9 Movement Patterns of a U-20 National Women's Soccer Team during Competitive Matches: Influence of Playing Position and Performance in the First Half
Reference: Int J Sports Med. 2017 Sep;38(10):747-754. doi: 10.1055/s-0043-110767. Epub 2017 Aug 7.
Authors: Ramos GP, Nakamura FY, Pereira LA, Junior WB, Mahseredjian F, Wilke CF, Garcia ES, Coimbra CC
Summary: The aim of this study was to determine the match locomotor characteristics of a sample of U-20 Brazilian female soccer players. Seven international matches were analyzed during the 2015 U-20 South American Championship, using global positioning technology. During a typical match, fullbacks and forwards covered greater distances in high-intensity running and sprinting than central defenders and midfielders (effect size [ES]=1.42-3.69). In the final 15 min of a game, total and high-intensity running distance and player load were ≈20 to 35% (ES=0.41-3.86) lower than in the first 15 min period for midfielders, fullbacks, forwards, and central defenders. Sprinting, and high-intensity running distances, and the frequency of accelerations >2 m.s-2 immediately after the most intense 5-min period declined in forwards (ES=1.78-2.67), fullbacks (ES=1.96-5.25), midfielders (ES=1.66-3.77), and central defenders (ES=1.50-4.22). Maintaining 'high' levels of activity in the first half resulted in ≈19% reductions in the second half for sprinting distance and frequency of accelerations >2 m.s-2 (ES=0.43 and 0.88), while increases in these locomotor activities were observed in situations with 'low' levels of activity (ES=0.64 and 1.12, for sprinting and accelerations >2 m.s-2, respectively) (within-subject analysis). The data demonstrate that high-intensity efforts are reduced during various phases of international matches and overall activity patterns vary among playing positions. This information could be useful in the development and prescription of sex- and age-specific training regimes.


#10 Sudden Cardiac Death in Professional Soccer Players

Reference: J Am Coll Cardiol. 2017 Sep 12;70(11):1420-1421. doi: 10.1016/j.jacc.2017.07.738.

Authors: Santos-Lozano A, Martin-Hernandez J, Baladron C, Turrado-Sevilla MA, Arraras-Flores A, Villacastin JP, Boraita A, Bueno H, Lucia A.


Australian Football
#1 The Use of Relative Speed Zones in Australian Football: Are We Really Measuring What We Think We Are?
Reference: Int J Sports Physiol Perform. 2017 Sep 5:1-25. doi: 10.1123/ijspp.2017-0148. [Epub ahead of print]
Authors: Murray NB, Gabbett TJ, Townshend AD
Summary: This study aimed to examine the difference between absolute and relative workloads, injury likelihood, and the acute:chronic workload ratio (ACWR) in elite Australian football. Forty-five elite Australian football players from one club participated in this study. Running workloads of players were tracked using Global Positioning System technology, and were categorised using either; (1) absolute, pre-defined speed thresholds, or (2) relative, individualised speed thresholds. Players were divided into three equal groups based on maximum velocity; (1) faster, (2) moderate, or (3) slower. One-week and four-week workloads were calculated, along with the ACWR. Injuries were recorded if they were non-contact in nature and resulted in "time-loss". Faster players demonstrated a significant overestimation of very high-speed running when compared to their relative thresholds (p=0.01, ES=-0.73). Similarly, slower players demonstrated an underestimation of high- (p=0.06, ES=0.55) and very high-speed (p=0.01, ES=1.16) running when compared to their relative thresholds. For slower players, (1) greater amounts of relative very high-speed running had a greater risk of injury than less (RR=8.30, p=0.04), and (2) greater absolute high-speed chronic workloads demonstrated an increase in injury likelihood (RR=2.28, p=0.16), while greater relative high-speed chronic workloads offered a decrease in injury likelihood (RR=0.33, p=0.11). Faster players with a very high-speed ACWR of >2.0 had a greater risk of injury than those between 0.49-0.99 for both absolute (RR=10.31, p=0.09) and relative (RR=4.28, p=0.13) workloads. The individualisation of velocity thresholds significantly alters the amount of very high-speed running performed and should be considered in the prescription of training load.


#2 The Influence of Rotations on Match Running Performance in Female Australian Football Midfielders
Reference: Int J Sports Physiol Perform. 2017 Sep 5:1-22. doi: 10.1123/ijspp.2017-0175. [Epub ahead of print]
Authors: Black GM, Gabbett TJ, Johnston RD, Naughton G, Cole MH, Dawson B
Summary: With female Australian football (AF) gaining popularity, the understanding of match demands is becoming increasingly important. The aim of this study compare running performances of rotated and whole-quarter state level female Australian Football players during match quarters. Twenty-two state-level female AF midfielders wore global positioning system units during 14 games to evaluate activity profiles. The Yo-Yo Intermittent Recovery Test (Level 1[Yo-Yo IR1]) was used as a measure of high-intensity running ability. Each player's data were categorised into either (1) whole-quarter (2) rotation bout 1 (3) rotation bout 2 before being further divided into quartiles. Players were separated into high or low Yo-Yo IR1 groups using a median split based on their Yo-Yo IR1 performance. Short (4-6 minutes), moderate (6-12 minutes) and long (12-18 minutes) on-field bout activity profiles were compared with whole-quarter players. Rotated players covered greater relative-and high-speed distances than whole-quarter players during a number of quartiles (Effect Size: ES, ≥0.44, Likelihood ≥94%). High Yo-Yo IR1 players covered greater relative and high-speed distances than low Yo-Yo IR1 players in rotation period 1. High Yo-Yo IR1 performance allowed players to cover greater relative distances (ES range=0.57-0.88) and high-speed distances (ES range=0.57-0.86) during rotations. No differences were reported between Yo-Yo IR1 groups when players were required to play whole quarters (ES ≤0.26, Likelihood ≤64%). Players who were on-field for short and moderate durations exhibited greater activity profiles than whole-quarter players. Rotated players have greater activity profiles than whole-quarter players. Additionally, superior high-speed running ability results in a greater activity profile than players who possess lower high-speed running ability. The findings also highlight the importance of short-to-moderate (4-12 minute) rotation periods and may be used to increase high-intensity running performances within quarters in female AF players.

Thu

21

Sep

2017

Football is...(#11)

Coaches not only determine the team's tactic, they also influence the intensity of training (if desired).

Wed

20

Sep

2017

Football is...(#10)

How to start off the 2nd half?

Mon

18

Sep

2017

Football is...(#9)

Jump-training needs to involve both directions - vertical and horizontal.

Fri

15

Sep

2017

Football is...(#8)

During different stages of the game or towards the end of the game....

Thu

14

Sep

2017

Latest research in football - week 35 - 2017

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Resistance training status and effectiveness of low frequency resistance training on upper-body strength and power in highly trained soccer players
Reference: J Strength Cond Res. 2017 Aug 26. doi: 10.1519/JSC.0000000000002202. [Epub ahead of print]
Authors: Hertzog M, Rumpf MC, Hader K
Summary: Soccer is classified as a contact/collision sport with many player-to-player duels. Winning these duels, shielding the ball or fending off an opponent requires upper-body strength and power. Therefore this study aimed, a) to examine the time-related effect of an upper-body RT on maximal strength and power changes in highly trained soccer players, b) to investigate if the resistance-training (RT) status influences these changes throughout a competitive season. Twenty-eight soccer players participated in this study and were divided into an untrained (UG) and a trained (TG) group, according to their RT status. Both groups performed the same upper-body RT once a week, over 30 weeks. Maximal strength (1RM) and maximal power (MP) were assessed before, during and after the competitive season. Both groups significantly improved 1RM and MP over the entire competitive season, with a moderate (TG, 13%) to very large (UG, 21%) magnitude in 1RM and with a small (TG, 8%) to moderate (UG, 13%) magnitude in MP. After the initial 10 weeks of RT, UG presented significant and slightly (1RM) to moderately (MP) greater improvements than TG. For all other time intervals, the between-groups changes in 1RM were rated as similar. For the last 20 weeks of the RT, the change in MP was significantly lower for UG compared to TG. One upper-body RT-session per week will provide sufficient stimulus to enable an almost certain improvement in strength and power throughout a competitive season for all players disregarding their initial RT status.


#2 Fundamental Tactical Principles of Soccer: A Comparison of Different Age Groups
Reference: J Hum Kinet. 2017 Aug 1;58:207-214. doi: 10.1515/hukin-2017-0078. eCollection 2017 Sep.
Authors: Borges PH, Guilherme J, Rechenchosky L, da Costa LCA, Rinadi W
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5548168/pdf/hukin-58-207.pdf
Summary: The fundamental tactical principles of the game of soccer represent a set of action rules that guide behaviours related to the management of game space. The aim of this study was to compare the performance of fundamental offensive and defensive tactical principles among youth soccer players from 12 to 17 years old. The sample consisted of 3689 tactical actions performed by 48 soccer players in three age categories: under 13 (U-13), under 15 (U-15), and under 17 (U-17). Tactical performance was measured using the System of Tactical Assessment in Soccer (FUT-SAT). The Kruskal Wallis, Mann-Whitney U, Friedman, Wilcoxon, and Cohen's Kappa tests were used in the study analysis. The results showed that the principles of "offensive coverage" (p = 0.01) and "concentration" (p = 0.04) were performed more frequently by the U-17 players than the U-13 players. The tactical principles "width and length" (p < 0.05) and "defensive unit" (p < 0.05) were executed more frequently by younger soccer players. It can be concluded that the frequency with which fundamental tactical principles are performed varies between the gaming categories, which implies that there is valuation of defensive security and a progressive increase in "offensive coverage" caused by increased confidence and security in offensive actions.


#3 High Speed Running and Sprinting Profiles of Elite Soccer Players
Reference: J Hum Kinet. 2017 Aug 1;58:169-176. doi: 10.1515/hukin-2017-0086. eCollection 2017 Sep.
Authors: Minano-Espin J, Casais L, Lago-Penas C, Gomez-Ruano MA
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5548164/pdf/hukin-58-169.pdf
Summary: Real Madrid was named as the best club of the 20th century by the International Federation of Football History and Statistics. The aim of this study was to compare if players from Real Madrid covered shorter distances than players from the opposing team. One hundred and forty-nine matches including league, cup and UEFA Champions League matches played by the Real Madrid were monitored during the 2001-2002 to the 2006-2007 seasons. Data from both teams (Real Madrid and the opponent) were recorded. Altogether, 2082 physical performance profiles were examined, 1052 from the Real Madrid and 1031 from the opposing team (Central Defenders (CD) = 536, External Defenders (ED) = 491, Central Midfielders (CM) = 544, External Midfielders (EM) = 233, and Forwards (F) = 278). Match performance data were collected using a computerized multiple-camera tracking system (Amisco Pro®, Nice, France). A repeated measures analysis of variance (ANOVA) was performed for distances covered at different intensities (sprinting (>24.0 km/h) and high-speed running (21.1-24.0 km/h) and the number of sprints (21.1-24.0 km/h and >24.0 km/h) during games for each player sectioned under their positional roles. Players from Real Madrid covered shorter distances in high-speed running and sprint than players from the opposing team (p < 0.01). While ED did not show differences in their physical performance, CD (p < 0.05), CM (p < 0.01), EM (p < 0.01) and F (p > 0.01) from Real Madrid covered shorter distances in high-intensity running and sprint and performed less sprints than their counterparts. Finally, no differences were found in the high-intensity running and sprint distances performed by players from Real Madrid depending on the quality of the opposition.


#4 The Predictors and Determinants of Inter-Seasonal Success in a Professional Soccer Team
Reference: J Hum Kinet. 2017 Aug 1;58:157-167. doi: 10.1515/hukin-2017-0084. eCollection 2017 Sep.
Authors: Kite CS, Nevill A
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5548163/pdf/hukin-58-157.pdf
Summary: The aims of this study were to 1) directly compare the performances of a professional soccer team over three seasons, 2) identify key variables that discriminated between a successful or unsuccessful performance, and 3) identify variables that best predicted success. ANOVA revealed that attempted and completed passes were significantly lower (both p < 0.001) in the most successful season (S1). Additionally, shot effectiveness was significantly less (p < 0.001) in their least successful season (S3) (vs S1 -11.61%; d = 0.735; vs S2 -12.02%; d = 0.760). When the match outcome was considered, they attempted significantly fewer passes when they won (-60.26; p = 0.002; d = -0.729) or drew (-44.87; p = 0.023; d = -0.543) compared to when they lost. The binary logistic regression analysis also retained passing variables. The team should attempt fewer passes, but ensure that more of these passes are completed. With away matches, the effect became more pronounced (β = -0.042, OR = 0.959, p = 0.012). In conclusion, the team should adopt a more direct style of play. They should move the ball into a shooting position with fewer passes and ensure that more shots are on the target.


#5 Effects of Plyometric Training and Beta-Alanine Supplementation on Maximal-Intensity Exercise and Endurance in Female Soccer Players
Reference: J Hum Kinet. 2017 Aug 1;58:99-109. doi: 10.1515/hukin-2017-0072. eCollection 2017 Sep.
Authors: Rosas F, Ramirez-Campillo R, Martinez C, Caniuqueo A, Canas-Jamet R, McCrudden E, Meylan C, Moran J, Nakamura FY, Pereira LA, Loturco I, Diaz D, Izquierdo M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5548158/pdf/hukin-58-099.pdf
Summary: Plyometric training and beta-alanine supplementation are common among soccer players, although its combined use had never been tested. Therefore, a randomized, double-blind, placebo-controlled trial was conducted to compare the effects of a plyometric training program, with or without beta-alanine supplementation, on maximal-intensity and endurance performance in female soccer players during an in-season training period. Athletes (23.7 ± 2.4 years) were assigned to either a plyometric training group receiving a placebo (PLACEBO, n = 8), a plyometric training group receiving beta-alanine supplementation (BA, n = 8), or a control group receiving placebo without following a plyometric training program (CONTROL, n = 9). Athletes were evaluated for single and repeated jumps and sprints, endurance, and change-of-direction speed performance before and after the intervention. Both plyometric training groups improved in explosive jumping (ES = 0.27 to 1.0), sprinting (ES = 0.31 to 0.78), repeated sprinting (ES = 0.39 to 0.91), 60 s repeated jumping (ES = 0.32 to 0.45), endurance (ES = 0.35 to 0.37), and change-of-direction speed performance (ES = 0.36 to 0.58), whereas no significant changes were observed for the CONTROL group. Nevertheless, compared to the CONTROL group, only the BA group showed greater improvements in endurance, repeated sprinting and repeated jumping performances. It was concluded that beta-alanine supplementation during plyometric training may add further adaptive changes related to endurance, repeated sprinting and jumping ability.


#6 Baseline Mechanical and Neuromuscular Profile of Knee Extensor and Flexor Muscles in Professional Soccer Players at the Start of the Pre-Season
Reference: J Hum Kinet. 2017 Aug 1;58:23-34. doi: 10.1515/hukin-2017-0066. eCollection 2017 Sep.
Authors: Garcia-Garcia O, Serrano-Gomez V, Hernandez-Mendo A, Morales-Sanchez V
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5548152/pdf/hukin-58-023.pdf
Summary: The aim of the study was to determine the mechanical and neuromuscular profile of knee extensor and flexor muscles in professional soccer players at the start of the pre-season, and to calculate percentages for symmetry, as well as examine differences according to the player's positional role. The vastus medialis (VM), vastus lateralis (VL), rectus femoris (RF) and biceps femoris (BF) of 16 professional soccer players were evaluated by means of tensiomyography (TMG) on the first day of the pre-season. A paired-samples t test (p < .05) was used to compare the dominant and non-dominant lower limb. One-way ANOVA was applied, with the positional role as an independent factor. No differences were observed between the dominant and non-dominant leg. The highest degree of symmetry corresponded to the VM (92.5 ± 2.7%), and the lowest to the BF (80.7 ± 10.9%). The positional role was associated with significant differences in some of the variables for the BF, RF and VM, although only the half-relaxation time in the BF and the time to sustain force in the VM differed across all the playing positions considered. TMG was shown to be a useful way of evaluating the neuromuscular characteristics of soccer players at the start of the pre-season, and of establishing baseline values for individual players.


#7 Relationship between Anxiety and Interleukin 10 in Female Soccer Players with and Without Premenstrual Syndrome (PMS)
Reference: Rev Bras Ginecol Obstet. 2017 Aug 28. doi: 10.1055/s-0037-1606244. [Epub ahead of print]
Authors: Foster R, Vaisberg M, Araujo MP, Martins MA, Capel T, Bachi ALL, Bella ZIKJ
Summary: The objective was to investigate the level of anxiety and its relationship with interleukin (IL)-10 (anti inflammatory cytokine that modulates mood swings) in a group of female soccer players. Fifty-two eumenorrheic soccer players were evaluated (age 19.8 ± 4.7 years). The presence of premenstrual syndrome (PMS) and phases of the menstrual cycle were determined by a daily symptom report (DSR) kept for 3 consecutive months. The concentration of cytokine IL-10 was determined from urine samples collected at four moments: at the follicular and luteal phases of the menstrual cycle, and before (pre) and after (post) the simulated game, and it was quantified by flow cytometry (Luminex xMAP - EMD Millipore, Billerica, MA, USA). The level of anxiety was determined through the BAI anxiety questionnaire answered by all athletes at the same time of the urine collection. The Student t-test, analysis of variance (ANOVA) and Pearson correlation with significance level at 5% were used for data analysis.  We showed that the prevalence of PMS among female soccer players is similar to that reported in the literature. In addition, we showed that the group with PMS has a higher level of anxiety compared with group without PMS (p = 0.002). Interleukin-10 analysis in players without PMS revealed that there was a significant decrease in the level of this cytokine before the game during the luteal phase when compared with the follicular phase (p < 0.05). The correlation analysis between IL-10 and anxiety showed a negative correlation post-game in the luteal phase in the group without PMS (p = 0.02; r = -0.50) and a positive correlation post-game in the luteal phase in PMS group (p = 0.04; r = 0.36).  Our results suggest that IL-10 may contribute to reduce anxiety in the group without PMS. This could be attributed to the fact that no IL-10 variation was observed in the group with PMS, which presented higher anxiety symptoms when compared with the group without PMS.


#8 Sprint mechanics return to competition follow-up after hamstring injury on a professional soccer player: A case study with an inertial sensor unit based methodological approach
Reference: J Biomech. 2017 Aug 20. pii: S0021-9290(17)30420-7. doi: 10.1016/j.jbiomech.2017.08.010. [Epub ahead of print]
Authors: Setuain I, Lecumberri P, Izquierdo M
Summary: The present research aimed to describe an inertial unit (IU)-based sprint mechanics evaluation model for assessing players' readiness to return to competition after suffering a grade I hamstring injury. A professional male football player (age 19years; height 177cm; weight 70kg, midfielder, Spanish, 3° Division) with a grade 1 biceps femoris injury was evaluated at pre-season, at return to play after injury and at the end of the competitive season. Sprint mechanics were analyzed via the use of an inertial orientation tracker (Xsens Technologies B.V. Enschede, Netherlands) attached over the L3-L4 region of the subject's lumbar spine. Sprint mechanics such as horizontal components of ground reaction force were assessed in both legs during sprinting actions. Findings and interpretation: Both the coefficient of the horizontal force application (SFV) and the ratio of forces (DRF) applied at increasing velocity were decreased in the injured limb compared with the contralateral healthy limb at the return to play evaluation (73% and 76% reductions, respectively) and returned to symmetrical levels at the end-season evaluation.


#9 The Brazilian World Cup: too hot for soccer?
Reference: Int J Biometeorol. 2017 Aug 25. doi: 10.1007/s00484-017-1425-y. [Epub ahead of print]
Authors: Lucena RL, Steinke ET, Pacheco C, Vieira LL, Betancour MO, Steinke VA
Summary: The main objective of this research was to analyze the climate data for the host cities of the soccer World Cup held in Brazil in June and July 2014. A great deal of criticism was expressed about the Brazilian climate in the national and international press and media in the run-up to the competition, suggesting that the air temperature and relative air humidity would be the main adversaries of the soccer teams, especially those from Europe, during the competition. An analysis of the weather was done at the places and times of each of the 64 matches held. A human thermal comfort index was calculated (discomfort index (DI)) for each of the matches in order to discover the real climatic conditions in the host cities during the 2014 World Cup and their potential influence on the teams and human comfort in general. During the 2014 World Cup, only two matches were played at temperatures above 30 °C, representing a negligible percentage of the total number of matches. The air temperature for over half the matches (53%) was 20-25 °C. The results showed the air temperature and relative humidity data analyzed here both individually and in the form of an index indicate that the World Cup held in Brazil in 2014 did not put any of the players at risk due to extreme heat.



American Football
#1 Prevalence and Impact of Glenoid Augmentation in American Football Athletes Participating in the National Football League Scouting Combine
Reference: Orthop J Sports Med. 2017 Aug 9;5(8):2325967117722945. doi: 10.1177/2325967117722945. eCollection 2017 Aug.
Authors: Knapik DM, Gillespie RJ, Salata MJ, Voos JE
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5555500/pdf/10.1177_2325967117722945.pdf
Summary: Bony augmentation of the anterior glenoid is used in athletes with recurrent shoulder instability and bone loss; however, the prevalence and impact of repair in elite American football athletes are unknown. The purpoas was to evaluate the prevalence and impact of glenoid augmentation in athletes invited to the National Football League (NFL) Scouting Combine from 2012 to 2015. A total of 1311 athletes invited to the NFL Combine from 2012 to 2015 were evaluated for history of either Bristow or Latarjet surgery for recurrent anterior shoulder instability. Athlete demographics, surgical history, imaging, and physical examination results were recorded using the NFL Combine database. Prospective participation data with regard to draft status, games played, games started, and status after the athletes' first season in the NFL were gathered using publicly available databases. Surgical repair was performed on 10 shoulders in 10 athletes (0.76%), with the highest prevalence in defensive backs (30%; n = 3). Deficits in shoulder motion were exhibited in 70% (n = 7) of athletes, while 40% (n = 4) had evidence of mild glenohumeral arthritis and 80% demonstrated imaging findings consistent with a prior instability episode (8 labral tears, 2 Hill-Sachs lesions). Prospectively, 40% (n = 4) of athletes were drafted into the NFL. In the first season after the combine, athletes with a history of glenoid augmentation were not found to be at significant risk for diminished participation with regard to games played or started when compared with athletes with no history of glenoid augmentation or athletes undergoing isolated shoulder soft tissue repair. After the conclusion of the first NFL season, 60% (n = 6 athletes) were on an active NFL roster. Despite being drafted at a lower rate than their peers, there were no significant limitations in NFL participation for athletes with a history of glenoid augmentation when compared with athletes without a history of shoulder surgery or those with isolated soft tissue shoulder repair. Glenohumeral arthritis and advanced imaging findings of labral tearing and Hill-Sachs lesions in elite American football players with a history of glenoid augmentation did not significantly affect NFL participation 1 year after the combine.


#2 Performance and Return to Sport After Clavicle Open Reduction and Internal Fixation in National Football League Players
Reference: Orthop J Sports Med. 2017 Aug 8;5(8):2325967117720677. doi: 10.1177/2325967117720677. eCollection 2017 Aug.
Authors: Jack RA 2nd, Sochacki KR, Navarro SM, McCulloch PC, Lintner DM, Harris JD
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5555514/pdf/10.1177_2325967117720677.pdf
Summary: Clavicle fractures are common injuries in professional football. Surgical fixation of these injuries may lead to decreased nonunion rates, improved shoulder strength, and decreased residual functional impairment. The purpoas of the study was to determine (1) return-to-sport (RTS) rate in National Football League (NFL) players after clavicle fracture open reduction and internal fixation (ORIF), (2) postoperative career length and games per season, (3) pre- and postoperative performance, and (4) postoperative performance compared with control players matched by position, age, years of experience, and performance. Publicly available records were used to identify players who underwent surgical treatment of a clavicle fracture while playing in the NFL. Demographic and performance data were collected for each player, and matched controls were identified. Control and case performance scores were calculated using a standardized scoring system. RTS was defined as playing in 1 NFL game after surgery. Comparisons between case and control groups at preoperative and postoperative time points were made using paired-samples Student t tests. Seventeen surgeries (16 players) were analyzed. Fifteen players (94.1%) were able to RTS in the NFL at a mean 211.3 ± 144.7 days postsurgery; 7 (44%) returned within the same season as their injury and subsequent fixation. The overall rate of a player's remaining in the NFL 1 year after surgery was 88.2%. Players who underwent surgery played in a similar number of games per season and had similar career lengths in the NFL as controls (P > .05). There were no significant (P > .05) differences between cases and matched controls presurgery and preindex. There was no difference (P > .05) in postoperative performance scores or games per season compared with preoperative scores or games per season for any position. Quarterbacks (n = 3, P = .049) and running backs (n = 5, P = .039) had significantly worse postoperative performance scores when compared with postindex matched controls. There is a high rate of RTS in the NFL after clavicle fracture ORIF. Players who underwent clavicle fracture ORIF played in a similar number of games per season and had similar career lengths in the NFL as controls. Quarterbacks and running backs had significantly worse postoperative performance scores when compared with postindex matched controls.


#3 Infographic: Effects of specific injury prevention programmes in football
Reference: Br J Sports Med. 2017 Aug 24. pii: bjsports-2017-098305. doi: 10.1136/bjsports-2017-098305. [Epub ahead of print]
Authors: Thorborg K, Krommes KK, Esteve E, Clausen MB, Bartels EM, Rathleff MS5, Thorborg K


#4 Injuries in Australian Rules Football: An Overview of Injury Rates, Patterns, and Mechanisms Across All Levels of Play
Reference: Sports Health. 2017 Aug 1:1941738117726070. doi: 10.1177/1941738117726070. [Epub ahead of print]
Authors: Saw R, Finch CF, Samra D, Baquie P, Cardoso T, Hope D, Orchard JW
Summary: The nature of Australian rules football (Australian football) predisposes both unique and common injuries compared with those sustained in other football codes. The game involves a combination of tackling, kicking, high-speed running (more than other football codes), and jumping. Two decades of injury surveillance has identified common injuries at the professional level (Australian Football League [AFL]). The objective was to provide an overview of injuries in Australian rules football, including injury rates, patterns, and mechanisms across all levels of play. A narrative review of AFL injuries, football injury epidemiology, and biomechanical and physiological attributes of relevant injuries. The overall injury incidence in the 2015 season was 41.7 injuries per club per season, with a prevalence of 156.2 missed games per club per season. Lower limb injuries are most prevalent, with hamstring strains accounting for 19.1 missed games per club per season. Hamstring strains relate to the volume of high-speed running required in addition to at times having to collect the ball while running in a position of hip flexion and knee extension. Anterior cruciate ligament injuries are also prevalent and can result from contact and noncontact incidents. In the upper limb, shoulder sprains and dislocations account for 11.5 missed games per club per season and largely resulted from tackling and contact. Concussion is less common in AFL than other tackling sports but remains an important injury, which has notably become more prevalent in recent years, theorized to be due to a more conservative approach to management. Although there are less injury surveillance data for non-AFL players (women, community-level, children), many of these injuries appear to also be common across all levels of play. An understanding of injury profiles and mechanisms in Australian football is crucial in identifying methods to reduce injury risk and prepare players for the demands of the game.


#5 Performance and Return to Sport After Forearm Fracture Open Reduction and Internal Fixation in National Football League Players
Reference: Hand (N Y). 2017 Aug 1:1558944717726137. doi: 10.1177/1558944717726137. [Epub ahead of print]
Author: Sochacki KR, Jack RA 2nd, Hirase T, McCulloch PC, Lintner DM, Liberman SR, Harris JD
Summary: Forearm fractures are one of the most common upper extremity injuries requiring surgery in professional football. Surgical fixation of forearm fractures may speed recovery and decrease games missed in football. National Football League (NFL) players who underwent forearm fracture open reduction and internal fixation (ORIF) were identified. Matched controls (position, age, experience, performance) were identified. Control and case performance scores were calculated using a standardized scoring system. Return to sport (RTS) in the NFL was defined as playing in a single NFL game after surgery. Comparisons between case and control groups and preoperative and postoperative time points were made using paired-samples Student t tests. Thirty-six surgeries were analyzed following ORIF. Thirty-three were able to RTS in the NFL at an average of 152.1 + 129.8 days. Controls had a significantly longer NFL career ( P < .001) and played in significantly more games per season ( P = .026) than players who underwent surgery. There was a significant ( P = .013) decrease in games/season for DBs following surgery. No significant difference was seen in postoperative performance scores compared with preoperative scores among any positions, nor in postoperative and postindex performance scores compared with matched controls. There is a high rate of RTS in the NFL following forearm fracture ORIF. Following surgery, players' careers were 1 year shorter and played nearly 2 fewer games per season than matched controls. Games per season following surgery was significantly lower among DBs when compared with presurgery. Postoperative performance scores were not significantly different compared with preoperative and when compared with matched controls.


#6 Sleep-Disordered Breathing and Cardiovascular Correlates in College Football Players
Reference: Am J Cardiol. 2017 Jul 25. pii: S0002-9149(17)31195-5. doi: 10.1016/j.amjcard.2017.07.030. [Epub ahead of print]
Authors: Kim JH, Hollowed C, Irwin-Weyant M, Patel K, Hosny K, Aida H, Gowani Z, Sher S, Gleason P, Shoop JL, Galante A, Clark C, Ko YA, Quyyumi AA, Collop NA, Baggish AL
Summary: This study sought to determine the cardiovascular physiologic correlates of sleep-disordered breathing (SDB) in American-style football (ASF) participants using echocardiography, vascular applanation tonometry, and peripheral arterial tonometry. Forty collegiate ASF participants were analyzed at pre- and postseason time points with echocardiography and vascular applanation tonometry. WatchPAT (inclusive of peripheral arterial tonometry) used to assess for SDB was then performed at the postseason time point. Twenty-two of 40 (55%) ASF participants demonstrated SDB with an apnea-hypopnea index (pAHI) ≥5. ASF participants with SDB were larger (109 ± 20 vs 92 ± 14 kg, p = 0.004) and more likely linemen position players (83% vs 50%, p = 0.03). Compared with those without SDB, ASF participants with SDB demonstrated relative impairments in left ventricular diastolic and vascular function as reflected by lower lateral e' (14 ± 3 vs 17 ± 3 cm/s, p = 0.007) and septal e' (11 ± 2 vs 13 ± 2 cm/s, p = 0.009) tissue velocities and higher pulse wave velocity (5.4 ± 0.9 vs 4.8 ± 0.5 m/s, p = 0.02). In the total cohort, there were significant positive correlations between pAHI and pulse wave velocity (r = 0.42, p = 0.008) and inverse correlations between pAHI and the averaged e' tissue velocities (r = -0.42, p = 0.01). In conclusion, SDB is highly prevalent in youthful collegiate ASF participants and associated with relative impairments in cardiac and vascular function. Targeted efforts to identify youthful populations with SDB, including ASF participants, and implement SDB treatment algorithms, represent important future clinical directives.


#7 Thermoregulatory and Perceptual Effects of a Percooling Garment Worn Underneath an American Football Uniform
Reference: J Strength Cond Res. 2017 Aug 26. doi: 10.1519/JSC.0000000000002207. [Epub ahead of print]
Authors: Keen ML, Miller KC, Zuhl MN
Summary: American football athletes are at the highest risk of developing exertional heat illness (EHI). We investigated whether percooling (i.e., cooling during exercise) garments affected perceptual or physiological variables in individuals exercising in the heat while wearing football uniforms. Twelve males (age=24±4y, mass=80.1±8.5kg, height=182.5±10.4cm) completed this cross-over, counterbalanced study. On day 1, we measured peak oxygen consumption (V[Combining Dot Above]O2). On days 2 and 3, participants wore percooling garments with (ICE) or without (CON) ice packs over the femoral and brachial arteries. They donned a football uniform and completed three, 20-minute bouts of treadmill exercise at ∼50% of peak V[Combining Dot Above]O2 (∼33°C, ∼42% relative humidity) followed by a 10-minute rest period. Ice packs were replaced every 20 minutes. Rating of perceived exertion (RPE), thermal sensation, and thirst sensation were measured before and after each exercise bout. Environmental symptom questionnaire (ESQ) responses and urine specific gravity (Usg) were measured pre-testing and after the last exercise bout. V[Combining Dot Above]O2, change in heart rate (ΔHR), and change in rectal temperature (ΔTrec) were measured every 5 minutes. Sweat rate, sweat volume, and percent hypohydration were calculated. No interactions (F17,187≤1.6, P≥0.1) or main effect of cooling condition (F1,11≤1.4, P≥0.26) occurred for ΔTrec, ΔHR, thermal sensation, thirst, RPE, ESQ, or Usg. No differences between conditions occurred for sweat volume, sweat rate, or percent hypohydration (t11≤0.7, P≥0.25). V[Combining Dot Above]O2 differed between conditions over time (F15,165=3.3, P<0.001); ICE was lower than CON at 30, 55, and 70 minutes (P<0.05). It is unlikely these garments would prevent EHI or minimize dehydration in football athletes.


Australian Football
#1 The relationship between repeated kicking performance and maximal aerobic capacity in elite junior Australian football
Reference: J Strength Cond Res. 2017 Aug 26. doi: 10.1519/JSC.0000000000002220. [Epub ahead of print]
Authors: Joseph J, Woods C, Joyce C
Summary: Australian football (AF) is a physically demanding game, requiring players to engage in a range of anaerobic activities interspersed with prolonged aerobic exercise. Coupled, players have to perform a range of technical skills, the most fundamental of which being to effectively kick (dispose) the ball. The aim of this study was to ascertain the extent to which aerobic capacity influenced kicking performance in AF. Twenty four elite U18 players competing in the same U18 competition performed the Australian Football Kicking test (AFK) three times with the yo-yo IR2 completed twice (between each AFK), with no rest between all three AFKs. Linear mixed models (LMM) reported the extent to which kicking speed and accuracy scores were influenced by the level reached on the yo-yo IR2. Results indicated that players who recorded a higher level on the yo-yo IR2 produced a faster average kicking speed following each AFK (P <0.01), while for all players, kicking speed was faster and more accurate on their dominant kicking leg regardless of score on the yo-yo IR2 (P <0.01). The LMMs also reported that those who maintained kicking speeds following two yo-yo IR2 also had higher competition kicking efficiency than those who reported reduced kicking speeds. These results show that aerobically proficient U18 AF players who attain a relatively higher score on the yo-yo IR2 may be better equipped at preserving their kicking speed. Thus, coaches may wish to integrate both technical and aerobic drills in an attempt to preserve a player's capability to execute ball disposals with a high velocity.

Thu

14

Sep

2017

Football is...(#7)

Being able to master different situations with the ball at a high pace can be decisive.

Wed

13

Sep

2017

Football is...(#6)

When its going up and down the field, make sure your players have enough (repeated) sprint ability in their tank.

Tue

12

Sep

2017

The Functional Movement Screen in Football

The Functional Movement Screen (FMS) was created to evaluate movement pattern quality for athletes as it thought that poor neuromuscular control increases the risk of acute injuries (8).

Based on this idea, the FMS would therefore serve as the basis for more complex movements (21) and consequently would be useful to identify functional movement deficits such as muscular imbalances/asymmetries (30), flexibility deficits (mobility) and balance or stability (5).

If you want to read the full-article you need to click HERE.

Mon

11

Sep

2017

Football is...(#5)

With the UEFA Champions League starting this week, players will face the first “real” congested schedule. In order to be fit for the next match, recovery is key.

Fri

08

Sep

2017

Football is...(#4)

Counterattack done correctly is deadly.

Thu

07

Sep

2017

Latest research in football - week 34 - 2017

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Including the Copenhagen Adduction Exercise in the FIFA 11+ Provides Missing Eccentric Hip Adduction Strength Effect in Male Soccer Players: A Randomized Controlled Trial
Reference: Am J Sports Med. 2017 Aug 1:363546517720194. doi: 10.1177/0363546517720194. [Epub ahead of print]
Authors: Haroy J, Thorborg K, Serner A, Bjorkheim A, Rolstad LE, Holmich P, Bahr R, Andersen TE
Summary: The FIFA 11+ was developed as a complete warm-up program to prevent injuries in soccer players. Although reduced hip adduction strength is associated with groin injuries, none of the exercises included in the FIFA 11+ seem to specifically target hip adduction strength. The purpose was to investigate the effect on eccentric hip adduction strength of the FIFA 11+ warm-up program with or without the Copenhagen adduction exercise. We recruited 45 eligible players from 2 U19 elite male soccer teams. Players were randomized into 2 groups; 1 group carried out the standard FIFA 11+ program, while the other carried out the FIFA 11+ but replaced the Nordic hamstring exercise with the Copenhagen adduction exercise. Both groups performed the intervention 3 times weekly for 8 weeks. Players completed eccentric strength and sprint testing before and after the intervention. Per-protocol analyses were performed, and 12 players were excluded due to low compliance (<67% of sessions completed). The main outcome was eccentric hip adduction strength (N·m/kg). Between-group analyses revealed a significantly greater increase in eccentric hip adduction strength of 0.29 Nm/kg (8.9%; P = .01) in favor of the group performing the Copenhagen adduction exercise, whereas no within-group change was noted in the group that used the standard FIFA 11+ program (-0.02 N·m/kg [-0.7%]; P = .69). Including the Copenhagen adduction exercise in the FIFA 11+ program increases eccentric hip adduction strength, while the standard FIFA 11+ program does not. Registration: Registration: ISRCTN13731446 (International Standard Randomised Controlled Trial Number registry).


#2 Balancing performance-based expectations with a holistic perspective on coaching: a qualitative study of Swedish women's national football team coaches' practice experiences
Reference: Int J Qual Stud Health Well-being. 2017 Dec;12(1):1358580. doi: 10.1080/17482631.2017.1358580.
Authors: Lindgren EC, Barker-Ruchti N
Summary: The purpose of this study was to explore how an exclusive sample of women's national football team coaches described how they implement careful coaching while facing social and organizational pressure to win medals. The purpose was to consider coaches' negotiations, we drew on Noddings' concept of caring. Using an interpretive research paradigm, we conducted in-depth interviews with five Swedish women's national football team coaches. An abductive approach was used to simultaneously process the theoretical framework of "ethics of care" and the empirical data. The coaches unanimously adopted a holistic perspective to coaching. The coaching strategies they described included promoting players' development, well-being, and sustainable elite performance; listening to the players' voices and engaging in dialogue; and creating a positive environment and promoting fair play. These findings demonstrate that the women coaches, despite performance pressure, adopt caring coaching in the form of Noddings' pedagogical modelling, dialogue, and confirmation strategies, and provide an example of how coaches can adopt caring, holistic, and athlete-centred coaching while working at the highest level of competitive sport and achieving competitive success.


#3 "Which pass is better?" Novel approaches to assess passing effectiveness in elite soccer
Reference: Hum Mov Sci. 2017 Aug 21;55:172-181. doi: 10.1016/j.humov.2017.07.010. [Epub ahead of print]
Authors: Rein R, Raabe D, Memmert D
Summary: Passing behaviour is a key property of successful performance in team sports. Previous investigations however have mainly focused on notational measurements like total passing frequencies which provide little information about what actually constitutes successful passing behaviour. Consequently, this has hampered the transfer of research findings into applied settings. Here we present two novel approaches to assess passing effectiveness in elite soccer by evaluating their effects on majority situations and space control in front of the goal. Majority situations are assessed by calculating the number of defenders between the ball carrier and the goal. Control of space is estimated using Voronoi-diagrams based on the player's positions on the pitch. Both methods were applied to position data from 103 German First division games from the 2011/2012, 2012/2013 and 2014/2015 seasons using a big data approach. The results show that both measures are significantly related to successful game play with respect to the number of goals scored and to the probability of winning a game. The results further show that on average passes from the mid-field into the attacking area are most effective. The presented passing efficiency measures thereby offer new opportunities for future applications in soccer and other sports disciplines whilst maintaining practical relevance with respect to tactical training regimes or game performances analysis.
 

#4 Hip abductor tendinitis after ACL reconstruction with patellar tendon graft in soccer players. A new clinical complication
Reference: Eur J Orthop Surg Traumatol. 2017 Aug 23. doi: 10.1007/s00590-017-2030-9. [Epub ahead of print]
Authors: Mouzopoulos G, Vlachos C, Tsembeli A, Karantzalis L, Vlachos K
Summary: Although ACL reconstruction remains a complex procedure with possible complications, affecting mainly the knee function, but no complications affecting the hip function have been already mentioned in the literature. Here in, we discuss the demographics, clinical course and outcomes of a rare complication such as hip abductors tendinitis, developed in soccer amateur athletes after ACL reconstruction with patellar tendon graft.


#5 Does a one year age gap modify the influence of age, maturation and anthropometric parameters as determinants of performance among youth elite soccer players?
Reference: J Strength Cond Res. 2017 Aug 22. doi: 10.1519/JSC.0000000000002203. [Epub ahead of print]
Authors: Bidaurrazaga-Letona I, Lekue JA, Amado M, Gil SM
Summary: Since age-groups in soccer often comprise children born within a two-year timeframe, characteristics that define the profile of a successful player may not be appropriate for the oldest or youngest players of the same age group. Therefore, this study aimed to determine to what extent performance was influenced by age, maturation and body size in elite soccer players with barely one year age gap. Anthropometry, 15-m sprint test, modified Barrow´s agility test, Yo-Yo intermittent recovery test level 1, countermovement jump, and handgrip test were conducted in players aged twelve and under (n=82, 11.1 ± 0.6 years; Mean ± SD) and between twelve and thirteen (n=79, 12.8 ± 0.6 years; Mean ± SD). A total score of performance, chronological age and age at peak height velocity were calculated. Descriptive statistics, Student's t-tests, and multiple linear regressions were performed. The explained variance in composite score was greater in the older (54%) than in the younger (30%) players. Sum of skinfolds was the primary predictor of 15-m sprint and countermovement jump in the younger group whereas in the older group chronological age and body size appeared as predictors of performance (41%). Body size explained the variance in most tests in older players. In the younger group biological maturity status explained the variance in endurance (35%) and handgrip (59%) tests. In summary, chronological age and sum of skinfolds influenced most tests; however, predictors differed between age groups. These findings highlight the importance of assessing individual differences in young male soccer players regardless of their similarity in age.


#6 The preventive effect of the bounding exercise programme on hamstring injuries in amateur soccer players: the design of a randomized controlled trial
Reference: BMC Musculoskelet Disord. 2017 Aug 22;18(1):355. doi: 10.1186/s12891-017-1716-9.
Authors: Van de Hoef S, Huisstede BMA, Brink MS, de Vries N, Goedhart EA, Backx FJG
Download link: https://bmcmusculoskeletdisord.biomedcentral.com/track/pdf/10.1186/s12891-017-1716-9?site=bmcmusculoskeletdisord.biomedcentral.com
Summary: Hamstring injuries are the most common muscle injury in amateur and professional soccer. Most hamstring injuries occur in the late swing phase, when the hamstring undergoes a stretch-shortening cycle and the hamstring does a significant amount of eccentric work. The incidence of these injuries has not decreased despite there being effective injury prevention programmes focusing on improving eccentric hamstring strength. As this might be because of poor compliance, a more functional injury prevention exercise programme that focuses on the stretch-shortening cycle might facilitate compliance. In this study, a bounding exercise programme consisting of functional plyometric exercises is being evaluated. A cluster-randomized controlled trial (RCT). Male amateur soccer teams (players aged 18-45 years) have been randomly allocated to intervention and control groups. Both groups are continuing regular soccer training and the intervention group is additionally performing a 12-week bounding exercise programme (BEP), consisting of a gradual build up and maintenance programme for the entire soccer season. The primary outcome is hamstring injury incidence. Secondary outcome is compliance with the BEP during the soccer season and 3 months thereafter. Despite effective hamstring injury prevention programmes, the incidence of these injuries remains high in soccer. As poor compliance with these programmes may be an issue, a new plyometric exercise programme may encourage long-term compliance and is expected to enhance sprinting and jumping performance besides preventing hamstring injuries.


#7 Allergies and Exercise-Induced Bronchoconstriction in a Youth Academy and Reserve Professional Soccer Team
Reference: Clin J Sport Med. 2017 Sep;27(5):450-456. doi: 10.1097/JSM.0000000000000393.
Authors: Bougault V, Drouard F, Legall F, Dupont G, Wallaert B
Summary: A high prevalence of respiratory allergies and exercise-induced bronchoconstriction (EIB) has been reported among endurance athletes. This study was designed to analyze the frequency of sensitization to respiratory allergens and EIB in young soccer players. Youth academy and reserve professional soccer team during the seasons 2012 to 2013 and 2013 to 2014. Eighty-five soccer players (mean age: 20 ± 4 years) participated in this study. Players underwent skin prick tests (SPTs) during the seasons 2012 to 2013 and 2013 to 2014. Spirometry and a eucapnic voluntary hyperpnea test were performed on soccer players during the first season 2012 to 2013 (n = 51) to detect EIB. Two self-administered questionnaires on respiratory history and allergic symptoms (European Community Respiratory Health Survey and Allergy Questionnaire for Athletes) were also distributed during both seasons (n = 59). The number of positive SPTs, exercise-induced respiratory symptoms, presence of asthma, airway obstruction, and EIB. Forty-nine percent of players were sensitized to at least one respiratory allergen, 33% reported an allergic disease, 1 player presented airway obstruction at rest, and 16% presented EIB. Factors predictive of EIB were self-reported exercise-induced symptoms and sensitization to at least 5 allergens. Questioning players about exercise-induced respiratory symptoms and allergies as well as spirometry at the time of the inclusion medical checkup would improve management of respiratory health of soccer players and would constitute inexpensive preliminary screening to select players requiring indirect bronchial provocation test or SPTs.


#8 Recent and Long-Term Soccer Heading Exposure Is Differentially Associated With Neuropsychological Function in Amateur Players
Reference: J Int Neuropsychol Soc. 2017 Aug 22:1-9. doi: 10.1017/S1355617717000790. [Epub ahead of print]
Authors: Levitch CF, Zimmerman ME, Lubin N, Kim N, Lipton RB, Stewart WF, Kim M, Lipton ML
Summary: The present study examined the relative contribution of recent or long-term heading to neuropsychological function in amateur adult soccer players. Soccer players completed a baseline questionnaire (HeadCount-12m) to ascertain heading during the prior 12 months (long-term heading, LTH) and an online questionnaire (HeadCount-2w) every 3 months to ascertain heading during the prior 2 weeks (recent heading, RH). Cogstate, a battery of six neuropsychological tests, was administered to assess neuropsychological function. Generalized estimating equations were used to test if LTH or RH was associated with neuropsychological function while accounting for the role of recognized concussion. A total of 311 soccer players completed 630 HeadCount-2w. Participants had an average age of 26 years. Participants headed the ball a median of 611 times/year (mean=1,384.03) and 9.50 times/2 weeks (mean=34.17). High levels of RH were significantly associated with reduced performance on a task of psychomotor speed (p=.02), while high levels of LTH were significantly associated with poorer performance on tasks of verbal learning (p=.03) and verbal memory (p=.04). Significantly better attention (p=.02) was detectable at moderately high levels of RH, but not at the highest level of RH. One hundred and seven (34.4%) participants reported a lifetime history of concussion, but this was not related to neuropsychological function and did not modify the association of RH or LTH with neuropsychological function. High levels of both RH and LTH were associated with poorer neuropsychological function, but on different domains. The clinical manifestations following repetitive exposure to heading could change with chronicity of exposure. (JINS, 2017, 23, 1-9).


#9 Variability of Metabolic Power Data in Elite Soccer Players During Pre-Season Matches
Reference: J Hum Kinet. 2017 Aug 1;58:233-245. doi: 10.1515/hukin-2017-0083. eCollection 2017 Sep.
Authors: Hoppe MW, Baumgart C, Slomka M, Polglaze T, Freiwald J
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5548171/pdf/hukin-58-233.pdf
Summary: This study aimed to determine the within-subject variability of GPS-derived metabolic power data in elite soccer players across several pre-season matches and compare the variability of high metabolic power, velocity, acceleration and deceleration running. Additionally, differences in metabolic power data among playing positions and relationships with various physical abilities were also investigated. Metabolic power data from 12 outfield starting players competing in the German Bundesliga were collected during five pre-season matches using GPS-technology (10 Hz). The players were also tested for speed, agility, power and intermittent endurance. Variability of global metabolic power data such as energy expenditure (CV = 2.2-7.0%) was lower than that for high-intensity including time ≥20 W·kg-1 (CV = 14.0-26.2%). Variability of high metabolic power (≥20 W·kg-1; CV = 14.1 ± 3.5%) was comparable to that of high velocity (≥15.5 km·h-1; CV = 17.0 ± 6.2%), acceleration (≥3 m·s-2; CV = 11.1 ± 5.1%) and deceleration running (≤-3 m·s-2; CV = 11.9 ± 4.5%) (p > 0.05, ES < 0.2). Defenders had a largely higher overall energy expenditure than midfielders and attackers (p < 0.01, ES > 0.6). Overall energy expenditure and cost were largely to very largely correlated with 5 m speed and 22 m agility sprint time and counter movement jump height (r = -0.70-0.69, p < 0.05). The detected variability indicates that global GPS-derived metabolic power data in elite soccer players from a single preseason match should be preferably used for practical applications. Contrary, high-intensity indicators should be interpreted cautiously and repeated match observations are recommended to establish meaningful high-intensity profiles of the players. Differences among playing positions and relationships with explosive physical abilities indicate that metabolic power analyses can provide new insights into the mechanics and energetics of soccer.


#10 Evaluation of the Illinois Change of Direction Test in Youth Elite Soccer Players of Different Age
Reference: J Hum Kinet. 2017 Aug 1;58:215-224. doi: 10.1515/hukin-2017-0079. eCollection 2017 Sep.
Authors: Negra Y, Chaabene H, Amara S, Jaric S, Hammami M, Hachana Y
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5548169/pdf/hukin-58-215.pdf
Summary: Change of direction ability is an essential pre-requisite in team sports athletes. The Illinois change of direction test has been routinely used for testing change of direction ability in soccer players. The aim of the present study was to evaluate the Illinois change of direction test in young elite soccer players in terms of its reliability, usefulness and relationship with body size. A total of one hundred and ninety-four male, national-level soccer players were recruited. They were classified into four age groups (U-8, U-10, U-12 and U-14). Participants were tested using the Illinois change of direction test twice, and basic indices of body size were obtained. The Illinois change of direction scores showed high relative and absolute reliability in all age groups (all intraclass correlation coefficients were >0.91, and the standard error of measurement was <5%). The usefulness analysis showed that the Illinois change of direction test could detect small changes in performance in the U-10 and U-12 groups. However, it could only detect moderate changes in performance in the U-8 and U-14 groups. Although the Illinois change of direction test detected significant performance differences among groups, scores were not significantly related to body size (-0.30<r<0.15; p > 0.05). Taking into account the test's high reliability and the appropriate level of usefulness, these results might support the use of the Illinois change of direction test as a standard measure for quantifying change of direction ability in young soccer players.


American Football
#1 Perceived Wellness Associated With Practice And Competition In Ncaa Division I Football Players
Reference: J Strength Cond Res. 2017 Aug 15. doi: 10.1519/JSC.0000000000002169. [Epub ahead of print]
Authors: Wellman AD, Coad SC, Flynn PJ, Siam TK, McLellan CP.
Summary: The present study assessed the influence of movement demands resulting from weekly practice sessions and games, on perceived wellness measurements taken post-game (Sunday) and 48 hours pre-game (Thursday) throughout the in-season period in National Collegiate Athletic Association (NCAA) division I football players. Thirty players were monitored using GPS receivers (Catapult Innovations OptimEye S5, Melbourne, Australia) during 12 games and 24 in-season practices. Movement variables included low-intensity distance, medium-intensity distance, high-intensity distance, sprint distance, total distance, player load, and acceleration and deceleration distance. Perceived wellness, including fatigue, soreness, sleep quality and quantity, stress, and mood, was examined using a questionnaire on a 1-5 Likert scale. Multi-level mixed linear regressions determined the differential effects of movement metrics on perceived wellness. Post-hoc tests were conducted to evaluate the pair-wise differentials of movement and significance for wellness ratings. Notable findings included significantly (p<0.05) less player load, low-intensity distance, medium-intensity distance, high-intensity distance, total distance, and acceleration and deceleration distance at all intensities, in those reporting more favorable (4-5) ratings of perceived fatigue and soreness on Sunday. Conversely, individuals reporting more favorable Sunday perceived stress ratings demonstrated significantly (p<0.05) higher player load, low-intensity and medium-intensity distance, total distance, low-intensity and medium-intensity deceleration distance, and acceleration distance at all intensities than individuals reporting less favorable (1-2) perceived stress ratings. Data from the present study provide a novel investigation of perceived wellness associated with college football practice and competition. Results support the use of wellness questionnaires for monitoring perceived wellness in NCAA division I college football players.


#2 Maximum distance and high speed distance demands by position in NCAA division I collegiate football games
Reference: J Strength Cond Res. 2017 Jul 5. doi: 10.1519/JSC.0000000000002105. [Epub ahead of print]
Authors: Sanders GJ, Roll B, Peacock CA
Summary: The purpose of the study was to quantify the average and maximum distances traveled by NCAA division I football athletes during competitive games. Utilizing global positioning system (GPS) devices (Catapult Sports), total and low, moderate and high speed distances were quantified by each position. Understanding maximal workloads can enhance conditioning practice periodization protocols. A total of 40 football athletes were included in the analysis. For the data to be included, athletes were required to participate in ≥ 75% of the offensive or defensive snaps for any given game. There was a total of 286 data downloads from 13 different games for eight different football positions. Data was calculated and compared by offensive and defensive position to establish the mean, standard deviation and maximum distances (m) traveled during competitive games. A total maximum distance range (Max Range) was established to account for athletes that accumulated in-game total distances greater than the M + 1SD for each position. A percent was also calculated to highlight how often athletes accumulated distance workloads in the Max Range. One-way ANOVA revealed there was a main effect of football position for all distance variables (p ≤ 0.001). Regardless of position, 12.0-16.7% of the time athletes accumulated in-game total distances in the Max Range. Conditioning and practice periodization protocols for distance should be position-specific or individualized to avoid under or over conditioning. Additionally, utilizing a Max Range for distance can help ensure athletes are achieving distance workloads that are similar to the demands of a competitive game.


#3 Movement Demands And Perceived Wellness Associated With Pre-Season Training Camp In Ncaa Division I College Football Players
Reference: J Strength Cond Res. 2017 Jul 5. doi: 10.1519/JSC.0000000000002106. [Epub ahead of print]
Authors: Wellman AD, Coad SC, Flynn PJ, McLellan CP, Climstein M
Summary: The aims of the present study were to examine the movement demands of pre-season practice in National Collegiate Athletic Association (NCAA) division I college football players using portable global positioning system (GPS) technology and to assess perceived wellness associated with pre-season practice to determine if GPS-derived variables from the preceding day influence perceived wellness the following day. Twenty-nine players were monitored using GPS receivers (Catapult Innovations, Melbourne, Australia) during 20 pre-season practices. Individual observations (n=550) were divided into offensive and defensive position groups. Movement variables including low-, medium-, high-intensity, and sprint distance, player load, and acceleration and deceleration distance were assessed. Perceived wellness ratings (n=469) were examined using a questionnaire which assessed fatigue, soreness, sleep quality, sleep quantity, stress, and mood. A one-way ANOVA for positional movement demands, and multi-level regressions for wellness measures were used, followed by post-hoc testing to evaluate the relational significance between categorical outcomes of perceived wellness scores and movement variables. Results demonstrated significantly (p<0.05) greater total, high-intensity, and sprint distance, along with greater acceleration and deceleration distances for the DB and WR position groups compared to their respective offensive and defensive counterparts. Significant (p<0.05) differences in movement variables were demonstrated for individuals who responded more or less favorably on each of the six factors of perceived wellness. Data from the present study provide novel quantification of the position-specific physical demands and perceived wellness associated with college football pre-season practice. Results support the use of position-specific training and individual monitoring of college football players.


#4 ACTN3 R577X Polymorphism Is Associated With the Incidence and Severity of Injuries in Professional Football Players
Reference: Clin J Sport Med. 2017 Aug 16. doi: 10.1097/JSM.0000000000000487. [Epub ahead of print]
Authors: Myosotis M, Sarah V, Claudia C, Francesco P, Paolo C, Xu Y, Nir E, Calo CM
Summary: The ACTN3 R577X gene variant results in the absence of the α-actinin-3 protein in ∼18% of humans worldwide and has been associated with athletic performance and increased susceptibility to eccentric muscle damage. The aim of this study was to investigate the association between ACTN3 R577X variant and indirect muscle disorders/injuries in professional football players. Two hundred fifty-seven male professional Italian football players (from Serie A, Primavera, Allievi, and Giovanissimi; age = 21.2 ± 5.3 years) and 265 nonathletic controls were recruited for the study. Genomic DNA was extracted using a buccal swab, and the ACTN3 R577X genotype was performed using a PCR method. Structural-mechanical injuries and functional muscle disorders were collected from a subgroup of 169 football players during the period of 2009 to 2014. We hypothesized that the 577XX genotype would be associated with higher predisposition to muscle injuries (compared with the other genotypes). ACTN3 XX (α-actinin-3 deficiency) players had 2.66 higher odds for an injury incidence than their ACTN3 RR counterparts (95% confidence interval [CI]: 1.09-6.63, P = 0.02), whereas RX and RR players had similar injury incidence. Furthermore, ACTN3 XX players had 2.13 higher odds for having a severe injury compared with their RR counterparts (95% CI: 1.25-3.74, P = 0.0054), whereas RX individuals had 1.63 higher odds for having a severe injury compared with the RR players (95% CI: 1.10-2.40, P = 0.015). The ACTN3 R577X polymorphism is associated with the incidence and severity of muscle injuries in professional football players; players with the ACTN3 577XX genotype have higher odds of having muscle injuries than their RR counterparts.Discovering the complex relationship between gene variants and muscle injuries may assist coaches, physiologists, and the medical community to development tailored injury prevention program for football players, which could provide a new edge for successful competition.


#5 Epidemiology of Injuries Identified at the NFL Scouting Combine and Their Impact on Performance in the National Football League: Evaluation of 2203 Athletes From 2009 to 2015
Reference: Orthop J Sports Med. 2017 Jul 24;5(7):2325967117708744. doi: 10.1177/2325967117708744. eCollection 2017 Jul.
Authors: Beaulieu-Jones BR, Rossy WH, Sanchez G, Whalen JM, Lavery KP, McHale KJ, Vopat BG, Van Allen JJ, Akamefula RA, Provencher MT
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5529031/pdf/10.1177_2325967117708744.pdf
Summary: At the annual National Football League (NFL) Scouting Combine, the medical staff of each NFL franchise performs a comprehensive medical evaluation of all athletes potentially entering the NFL. Currently, little is known regarding the overall epidemiology of injuries identified at the combine and their impact on NFL performance. The purpose was to determine the epidemiology of injuries identified at the combine and their impact on initial NFL performance. All previous musculoskeletal injuries identified at the NFL Combine from 2009 to 2015 were retrospectively reviewed. Medical records and imaging reports were examined. Game statistics for the first 2 seasons of NFL play were obtained for all players from 2009 to 2013. Analysis of injury prevalence and overall impact on the draft status and position-specific performance metrics of each injury was performed and compared with a position-matched control group with no history of injury or surgery. A total of 2203 athletes over 7 years were evaluated, including 1490 (67.6%) drafted athletes and 1040 (47.2%) who ultimately played at least 2 years in the NFL. The most common sites of injury were the ankle (1160, 52.7%), shoulder (1143, 51.9%), knee (1128, 51.2%), spine (785, 35.6%), and hand (739, 33.5%). Odds ratios (ORs) demonstrated that quarterbacks were most at risk of shoulder injury (OR, 2.78; P = .001), while running backs most commonly sustained ankle (OR, 1.39; P = .040) and shoulder injuries (OR, 1.55; P = .020) when compared with all other players. Ultimately, defensive players demonstrated a greater negative impact due to injury than offensive players, with multiple performance metrics significantly affected for each defensive position analyzed, whereas skilled offensive players (eg, quarterbacks, running backs) demonstrated only 1 metric significantly affected at each position. The most common sites of injury identified at the combine were (1) ankle, (2) shoulder, (3) knee, (4) spine, and (5) hand. Overall, performance in the NFL tended to worsen with injury history, with a direct correlation found between injury at a certain anatomic location and position of play. Defensive players tended to perform worse compared with offensive players if injury history was present.


Australian Football
#1 Concussion Incidence and Recurrence in Professional Australian Football Match-Play: A 14-Year Analysis
Reference: J Sports Med (Hindawi Publ Corp). 2017;2017:2831751. doi: 10.1155/2017/2831751. Epub 2017 Jul 19.
Authors: Gibbs N, Watsford M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5540267/pdf/JSM2017-2831751.pdf
Summary: Concussion incidence rates in professional Australian football may be underreported due to the injury classification definition. A myriad of factors contribute to concussion risk; however, there is limited long-term surveillance in Australian football. This study analysed concussion in one Australian football team over an extended period. Match-play concussion injuries in one team (n = 116 participants) were diagnosed and treated by the team physician over 14 years. Analysis of factors related to concussion including matches played, time of day and season, and return to play provided an insight into occurrence and recurrence rates. 140 concussions were recorded (17.6 per 1000 player match hours). A strong relationship was evident between matches played and concussion incidence (r = 0.70) and match conditions did not negatively affect the concussion rate. Whether an athlete returned to play in the same match or suffered a loss-of-consciousness concussion (p = 0.84), their ensuing rate of concussion was not affected. Concussion in professional Australian football was related to the number of matches played. Further, neither previous incidence nor loss of consciousness affected future concussion risk. This study provides ecologically valid evidence of the concussion incidence rate in professional Australian football and has implications for the management of athletes sustaining concussion injuries.

Thu

07

Sep

2017

Football...(#3)

Sprinting in football is an important activity, here are some crucial information.

Wed

06

Sep

2017

Football is...(#2)

High-intensity running for footballers - one suggestion.

Tue

05

Sep

2017

Football is...(#1)

Just in case there were some crucial set-pieces for some teams in the World Cup Qualifiers...

Fri

25

Aug

2017

Latest research in football - week 33 - 2017

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Effects of Inhaled Salbutamol on Sport-Specific Fitness of Non-Asthmatic Football Players
Reference: Acta Med Iran. 2017 May;55(5):324-332.
Authors: Halabchi F, Abarashi M, Mansournia MA, Seifbarghi T
Download link: acta.tums.ac.ir/index.php/acta/article/download/5850/4939
Summary: In this article, we investigated the effectiveness of inhaled salbutamol withtherapeutic dose on the sport-specific performance of non-asthmatic young football players. In a double-blinded, randomised placebo controlled trial with 2-treatment, 2-period crossover design, twenty participants who were non-asthmatic junior professional football players were randomly allocated to two groups. Fifteen minutes before sport-specific fitness testing, each group randomly received 2 inhalations (200 micrograms) of salbutamol or placebo, respectively. After 1 week wash-out period, each participant has tested again, this time with the alternative inhaler. The primary outcomes were the differences between salbutamol and placebo groups in six tests of 7×30-m repeated sprint, Loughborough soccer dribbling, vertical jump, agility, Loughborough soccer passing, 20-m multistage shuttle run. A total of twenty players did two test batteries completely. There was no significant difference between salbutamol and placebo users in the tests [Treatment effect (CI95%); 7×30 sprint: -2.4 (-7.6-2.9), dribbling: -3.8 (-12.2-4.5), vertical jump: -1.2 (-3.7-1.3), agility: -0.4 (-0.9-0.1), passing: 0.2 (-12-12.4), shuttle run distance: -112 (-503.2-279.2)]. Furthermore, no period or carry-over effects were detected. It seems that single therapeutic dose of inhaled salbutamol (200 micrograms) does not appear to improve football related performance.


#2 Heading for trouble: is dementia a game changer for football?
Reference: Br J Sports Med. 2017 Jul 20. pii: bjsports-2017-097627. doi: 10.1136/bjsports-2017-097627. [Epub ahead of print]
Authors: Rutherford A, Stewart W, Bruno D


#3 Infographics: Injury prevention exercise programmes: what are the perceptions of programme deliverers in the academy football setting?
Reference: Br J Sports Med. 2017 Jul 22. pii: bjsports-2017-097774. doi: 10.1136/bjsports-2017-097774. [Epub ahead of print]
Authors: Bekker S, Finch CF, O Brien J


#4 Fixture congestion modulates post-match recovery kinetics in professional soccer players
Reference: Res Sports Med. 2017 Aug 10:1-13. doi: 10.1080/15438627.2017.1365296. [Epub ahead of print]
Authors: Lundberg TR, Weckstrom K
Summary: This study examined the influence of fixture congestion on physical performance and biochemical variables in professional male footballers. After 3 competitive matches within a week (3M cycle), 16 players underwent blood sampling and field testing 72 h after the last match. The same tests were performed after a regular 1 match-week cycle (1M cycle). The 1M vs. 3M change scores were compared between Congested (high match exposure) and non-selected Control players. The change score in muscle soreness was greater (effect size 1.0; CI 0.0-1.9) in the Congested players than Controls, indicating a possible negative effect of fixture congestion. There were no effects on sprint and jump performance. The change in plasma (P)-Urea was greater in Congested players than controls (effect size 1.3; CI 0.3-2.2). The effects on other blood variables were either non-existing/trivial, or unclear. Altogether, physical fitness and immune function were not compromised by match congestion, yet some indices of physiological stress and muscle damage were still evident.


#5 Patellar tendinopathy in young elite soccer- clinical and sonographical analysis of a German elite soccer academy
Reference: BMC Musculoskelet Disord. 2017 Aug 8;18(1):344. doi: 10.1186/s12891-017-1690-2.
Authors: Bode G, Hammer T, Karvouniaris N, Feucht MJ, Konstantinidis L, Sudkamp NP, Hirschmuller A
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5549401/pdf/12891_2017_Article_1690.pdf
Summary: The prevalence of patellar tendinopathy is elevated in elite soccer compared to less explosive sports. While the burden of training hours and load is comparably high in youth elite players (age < 23 years), little is known about the prevalence of patellar tendinopathy at this age. There is only little data available on the influence of age, the amount of training, the position on the field, as well as muscular strength, range of motion, or sonographical findings in this age group. The purpose of the present study was to examine the above-mentioned parameters in all age groups of a German youth elite soccer academy. One hundred nineteen male youth soccer players (age 15,97 ± 2,24 years, height 174, 60 ± 10,16 cm, BMI 21, 24 ± 2,65) of the U-13 to U-23 teams were part of the study. Data acquisition included sport specific parameters such as footwear, amount of training hours, leg dominance, history of tendon pathologies, and clinical examination for palpatory pain, indurations, muscular circumference, and range of motion. Subjective complaints were measured with the Victorian Institute of Sport Assessment Patellar (VISA-P) Score. Furthermore, sonographical examinations (Aplio SSA-770A/80; Toshiba, Tokyo, Japan) with 12-MHz multifrequency linear transducers (8-14 MHz) of both patellar tendons were performed with special emphasis on hyper- and hypo echogenic areas, diameter and neovascularization. The prevalence of patellar tendinopathies was 13.4%. Seventy-five percent of the players complained of pain of their dominant leg with onset of pain at training in 87.5%. The injured players showed a medium amount of 10.34 ± 3.85 training hours and a medium duration of symptoms of 11.94 ± 18.75 weeks. Two thirds of players with patellar tendinopathy were at the age of 15-17 (Odds ratio 1.89) while no differences between players of the national or regional league were observed. In case of patellar tendinopathy, VISA-P was significantly lower in comparison to healthy players (mean ± SD 76.80 ± 28.56 points vs. 95.85 ± 10.37). The clinical examination revealed local pain at the distal patella, pain at stretching, and thickening of the patellar tendon (p = 0.02). The mean tendon diameter measured 2 cm distally to the patella was 4.10 ± 0.68 mm with a significantly increased diameter of 0.15 mm in case of an underlying tendinopathy (p = 0.00). The incidence of hypo-echogenic areas and neovascularizations was significantly elevated in players with patellar tendon syndrome (PTS) (p = 0.05). The prevalence of patellar tendinopathy in youth elite soccer is relatively high in comparison to available data of adult players. Especially players at the age of 15 to 17 are at considerable risk. Tendon thickening, hypo-echogenic areas, and neovascularization are more common in tendons affected by PTS.


#6 The Effects of Maturation on Measures of Asymmetry During Neuromuscular Control Tests in Elite Male Youth Soccer Players
Reference: Pediatr Exerc Sci. 2017 Aug 8:1-23. doi: 10.1123/pes.2017-0081. [Epub ahead of print]
Authors: Read PJ, Oliver JL, Myer GD, De Ste Croix MBA, Lloyd RS
Summary: Asymmetry is a risk factor for male youth soccer players. There is a paucity of data confirming the presence of asymmetry using practically viable screening tasks in players at different stages of maturation. A cross sectional sample (N = 347) of elite male youth soccer players who were either (pre-, circa- or post-peak height velocity (PHV)) completed the following single leg assessments: Y-Balance anterior reach (Y-Bal); hop for distance (SLHD); 75% hop and stick (75%Hop) and countermovement jumps (SLCMJ). SLCMJ landing force asymmetry was higher in both circa and post-PHV groups, (p < 0.001; d = 0.41 - 0.43). 75%Hop landing force asymmetries were also highest in circa PHV players but between group comparisons were not statistically significant and effect sizes were small. SLHD and Y-Bal asymmetries reduced with maturation; however, no group differences were significant, with small to trivial effect sizes (d = ≤ 0.25). Stage of maturation did not have a profound effect on asymmetry. Between-limb differences in functional performance seem to be established in early childhood; thus, targeted interventions to reduce this injury risk factor should commence in pre-PHV athletes and be maintained throughout childhood and adolescence to ensure asymmetry does not increase.


#7 Characteristics of the Foot Static Alignment and the Plantar Pressure Associated with Fifth Metatarsal Stress Fracture History in Male Soccer Players: a Case-Control Study
Reference: Sports Med Open. 2017 Dec;3(1):27. doi: 10.1186/s40798-017-0095-y. Epub 2017 Aug 7.
Authors: Matsuda S, Fukubayashi T, Hirose N
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5545985/pdf/40798_2017_Article_95.pdf
Summary: There is a large amount of information regarding risk factors for fifth metatarsal stress fractures; however, there are few studies involving large numbers of subjects. This study aimed to compare the static foot alignment and distribution of foot pressure of athletes with and without a history of fifth metatarsal stress fractures. The study participants comprised 335 collegiate male soccer players. Twenty-nine with a history of fifth metatarsal stress fractures were in the fracture group and 306 were in the control group (with subgroups as follows: 30 in the fracture foot group and 28 in the non-fracture group). We measured the foot length, arch height, weight-bearing leg-heel alignment, non-weight-bearing leg-heel alignment, forefoot angle relative to the rearfoot, forefoot angle relative to the horizontal axis, and foot pressure. The non-weight-bearing leg-heel alignment was significantly smaller and the forefoot angle relative to the rearfoot was significantly greater in the fracture foot group than in the control foot group (P = 0.049 and P = 0.038, respectively). With regard to plantar pressure, there were no significant differences among the groups. Midfield players had significantly higher rates of fifth metatarsal stress fracture in their histories, whereas defenders had significantly lower rates (chi-square = 13.2, P < 0.05). There were no significant differences in the frequency of fifth metatarsal stress fractures according to the type of foot (kicking foot vs. pivoting foot) or the severity of ankle sprain. Playing the midfield position and having an everted rearfoot and inverted forefoot alignment were associated with fifth metatarsal stress fractures. This information may be helpful for preventing fifth metatarsal stress fracture recurrence. More detailed load evaluations and a prospective study are needed in the future.


#8 The psycho-hormonal influence of anaerobic fatigue on semi-professional female soccer players
Reference: Physiol Behav. 2017 Aug 4;180:8-14. doi: 10.1016/j.physbeh.2017.07.031. [Epub ahead of print]
Authors: Broodryk A, Pienaar C, Edwards D, Sparks M
Summary: Globally it is assumed that high-intensity activities are the general cause of fatigue experienced during a soccer match. However, little is known about the hormonal and psychological effects of fatigue due to these activities on semi-professional female soccer players. Forty-seven female players (22.0±2.7y) from a tertiary education institution volunteered for the study. Their cortisol values (saliva sample), anxiety [Spielberger State-trait anxiety inventory questionnaire (STAI)] and mood scores [Incredible Short Profile of Mood states questionnaire (ISP)] were taken an hour and immediately prior to, and 15min after an anaerobic fatiguing test (AFT). During the AFT, subjects completed a 5-m multiple shuttle run test and their HRmax, blood lactate (BLa-) and rate of perceived exertion (RPE) taken afterwards. Anxiety scores were divided into three categories and mood scores into the Total Mood Disturbances (TMD) and six subscales. The results indicated an increase in cortisol, psychological fatigue and TMD from baseline and/or pre- to post-AFT (p<0.05). Vigour and confusion decreased from baseline and/or pre- to post-AFT (p<0.05). A relationship was seen between state-anxiety and TMD (r≥0.63, p<0.05) at all three time points, as well as between state-anxiety and HRmax (r=0.37, p=0.03). Cortisol and RPE (r=-0.34, p=0.03) demonstrated a correlation post-AFT. This is the first study to evaluate the effects of anaerobic fatigue on the hormonal and psychological states of female soccer players. The results suggest that an AFT can be perceived as a physiological and psychological stressor by female players, hence has the ability to influence performance. Altering a player's awareness and anaerobic fitness level might therefore influence both the hormonal and psychological consequences of the stressor, subsequently reducing the experience of fatigue and thereby enhancing performance.


#9 Pubertal development of body size and soccer-specific functional capacities in adolescent players
Reference: Res Sports Med. 2017 Aug 17:1-16. doi: 10.1080/15438627.2017.1365301. [Epub ahead of print]
Authors: Carvalho HM, Lekue JA, Gil SM, Bidaurrazaga-Letona I
Summary: Pubertal growth in body size and functional capacities were examined in adolescent soccer players (n = 33). The average age at baseline was 10.9 (9.8-11.8 years). Peak height velocity (PHV) and growth curves for body mass and functional performance (countermovement jump, 15-m sprint, agility and Yo-Yo intermittent recovery test - level 1) were determined with Bayesian multilevel models. Estimates for PHV and age at PHV were 8.1 cm/year (95% credible interval: 4.2-18.5 cm/year) and 12.9 years (95% credible interval: 11.8-15.5 years), respectively. Peak body mass velocity occurred 0.48 year after PHV. Jump performance maximum velocity occurred about 2 years after PHV and peak sprint performance maximum velocity was coincident with PHV. Agility and intermittent endurance run performance showed a quadratic trend of improvement of performance, starting to level off at about 3-4 years after PHV. The modelling procedures were efficient to determine pubertal growth curves aligned for chronological age and age at PHV, considering individual differences in maturation when interpreting the development of performance in youth soccer.


#10 Effect of Changes in Artificial Turf on Sports Injuries in Male University Soccer Players
Reference: Orthop J Sports Med. 2017 Aug 2;5(8):2325967117719648. doi: 10.1177/2325967117719648. eCollection 2017 Aug.
Authors: Fujitaka K, Taniguchi A, Kumai T, Otuki S, Okubo M, Tanaka Y
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5544152/pdf/10.1177_2325967117719648.pdf
Summary: Studies comparing the types and severity of trauma and injuries caused by different types of field surfaces have been conducted. However, there have been no studies on sports injuries caused by temporal deterioration of long-pile artificial turf fields and related decreases in the rubber chip and silica sand infill. The purpose was to investigate the influence of an artificial turf field on sports injuries in a university soccer team. A total of 397 male soccer players who were members of a single university soccer team were surveyed over a 12-year period, from April 2003 to March 2015. During this period, the team played for 4 years on a soil field (2003-2006) and 8 years on artificial turf (2007-2014). We analyzed the effect of changes in the artificial turf on the incidence rate of sports injuries (injury rate per 1000 athlete-exposures). We calculated the incidence rate of injuries sustained by the team and compared the results for each year of the study. After conversion of the field to artificial turf, there was a significant increase in the incidence of upper extremity trauma (P < .05). There was a significant increase in lower extremity sprains from 2007 to 2008, 1 year after the conversion from soil to artificial turf (P < .05). Analysis of the incidence of lower extremity muscle strain indicated that although the injury rate increased progressively, it decreased significantly after the insertion of additional rubber chips in 2014 (P < .05). After conversion to artificial turf, there was a significant increase in the incidence of upper extremity trauma. After the refurbishing with additional rubber chips, the incidence of lower extremity muscle strain significantly declined. When analyzing measures that could prevent sports injuries related to soccer, it is necessary to take into consideration the changes that occur to the artificial turf over time.


#11 The influence of speed abilities and technical skills in early adolescence on adult success in soccer: A long-term prospective analysis using ANOVA and SEM approaches
Reference: PLoS One. 2017 Aug 14;12(8):e0182211. doi: 10.1371/journal.pone.0182211. eCollection 2017.
Authors: Honer O, Leyhr D, Kelava A
Download link: http://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0182211&type=printable
Summary: Several talent development programs in youth soccer have implemented motor diagnostics measuring performance factors. However, the predictive value of such tests for adult success is a controversial topic in talent research. This prospective cohort study evaluated the long-term predictive value of 1) motor tests and 2) players' speed abilities (SA) and technical skills (TS) in early adolescence. The sample consisted of 14,178 U12 players from the German talent development program. Five tests (sprint, agility, dribbling, ball control, shooting) were conducted and players' height, weight as well as relative age were assessed at nationwide diagnostics between 2004 and 2006. In the 2014/15 season, the players were then categorized as professional (n = 89), semi-professional (n = 913), or non-professional players (n = 13,176), indicating their adult performance level (APL). The motor tests' prognostic relevance was determined using ANOVAs. Players' future success was predicted by a logistic regression threshold model. This structural equation model comprised a measurement model with the motor tests and two correlated latent factors, SA and TS, with simultaneous consideration for the manifest covariates height, weight and relative age. Each motor predictor and anthropometric characteristic discriminated significantly between the APL (p < .001; η2 ≤ .02). The threshold model significantly predicted the APL (R2 = 24.8%), and in early adolescence the factor TS (p < .001) seems to have a stronger effect on adult performance than SA (p < .05). Both approaches (ANOVA, SEM) verified the diagnostics' predictive validity over a long-term period (≈ 9 years). However, because of the limited effect sizes, the motor tests' prognostic relevance remains ambiguous. A challenge for future research lies in the integration of different (e.g., person-oriented or multilevel) multivariate approaches that expand beyond the "traditional" topic of single tests' predictive validity and toward more theoretically founded issues.


American Football
#1 The Effects of Cardiovascular Fitness and Body Composition on Maximal Core Temperature in Collegiate Football Players During Pre-season
Reference: J Strength Cond Res. 2017 Jul 14. doi: 10.1519/JSC.0000000000002027. [Epub ahead of print]
Authors: McClelland JM, Godek SF, Chlad PS, Feairheller DL, Morrison KE
Summary: This study evaluated the effects of BMI and aerobic fitness (VO2max) on maximal core temperature values (Tcmax) in 17 NCAA Division III football players during pre-season. The subjects included nine backs (BKs) and eight linemen (LM). VO2max testing was performed one week prior to pre-season. Core temperature was monitored via ingestible sensor every 10 min during practices on day 4(D1), day 5(D2), day 7(D3), and post-acclimatization on day 14(D4). Wet bulb globe temperature (WBGT) was recorded on each collection day. Independent, paired t-tests and Pearson's correlations were performed (α=0.05). There were no significant correlations between VO2max and Tcmax on D1 (WBGT=29.07°C) or D2 (WBGT=30.93°C), but on D3 (WBGT=31.39 °C) there was a non-significant moderate negative correlation (r=-0.564, P=0.090). There were no significant correlations between BMI and Tcmax on D1or D2, but on D3 there was a non-significant moderate positive correlation (r=0.596, P=0.069). Paired t-tests revealed that overall Tcmax (D1-3) (38.56±0.32°C) was statistically higher (P=0.002) than D4 (38.16±0.30 °C). Independent t-tests between groups showed the Tcmax values during pre-acclimatization (D1-D3) were significantly higher in LM (38.50±0.37°C) than BKs (38.16±0.35°C) (P=0.007). VO2max was significantly lower (P=0.006) in LM [36.89±6.40 ml/kg•min] than BKs [47.44±7.09 ml/kg•min] and BMI was significantly higher (P=0.019) in LM (35.59±4.00 kg/m) than BKs (28.68±3.38 kg/m). The results of this study demonstrate that LM are significantly less fit than BKs and have a greater BMI. When WBGT was the highest on D3, the results suggest that those with lower VO2max and higher BMI experienced a higher Tcmax.


#2 Temperate-Water Immersion as a Treatment for Hyperthermic Humans Wearing American Football Uniforms
Reference: J Athl Train. 2017 Jul 17. doi: 10.4085/1062-6050-52.5.05. [Epub ahead of print]
Authors: Miller KC, Truxton T, Long B
Summary: Cold-water immersion (CWI; 10°C) can effectively reduce body core temperature even if a hyperthermic human is wearing a full American football uniform (PADS) during treatment. Temperate-water immersion (TWI; 21°C) may be an effective alternative to CWI if resources for the latter (eg, ice) are unavailable. The purpose was to measure rectal temperature (Trec) cooling rates, thermal sensation, and Environmental Symptoms Questionnaire (ESQ) scores of participants wearing PADS or shorts, undergarments, and socks (NOpads) before, during, and after TWI. Thirteen physically active, unacclimatized men (age = 22 ± 2 years, height = 182.3 ± 5.2 cm, mass = 82.5 ± 13.4 kg, body fat = 10% ± 4%, body surface area = 2.04 ± 0.16 m2). Participants exercised in the heat (40°C, 50% relative humidity) on 2 days while wearing PADS until Trec reached 39.5°C. Participants then underwent TWI while wearing either NOpads or PADS until Trec reached 38°C. Thermal sensation and ESQ responses were collected at various times before and after exercise. Temperate-water immersion duration (minutes), Trec cooling rates (°C/min), thermal sensation, and ESQ scores were used as outcome measures. Participants had similar exercise times (NOpads = 38.1 ± 8.1 minutes, PADS = 38.1 ± 8.5 minutes), hypohydration levels (NOpads = 1.1% ± 0.2%, PADS = 1.2% ± 0.2%), and thermal sensation ratings (NOpads = 7.1 ± 0.4, PADS = 7.3 ± 0.4) before TWI. Rectal temperature cooling rates were similar between conditions (NOpads = 0.12°C/min ± 0.05°C/min, PADS = 0.13°C/min ± 0.05°C/min; t12 = 0.82, P = .79). Thermal sensation and ESQ scores were unremarkable between conditions over time. Temperate-water immersion produced acceptable (ie, >0.08°C/min), though not ideal, cooling rates regardless of whether PADS or NOpads were worn. If a football uniform is difficult to remove or the patient is noncompliant, clinicians should begin water-immersion treatment with the athlete fully equipped. Clinicians should strive to use CWI to treat severe hyperthermia, but when CWI is not feasible, TWI should be the next treatment option because its cooling rate was higher than the rates of other common modalities (eg, ice packs, fanning).


#3 Influence of Body Composition on Functional Movement Screen™ Scores in Collegiate Football Players
Reference: J Sport Rehabil. 2017 Jul 17:1-21. doi: 10.1123/jsr.2015-0080. [Epub ahead of print]
Authors: Nicolozakes CP, Schneider DK, Rower B, Borchers J, Hewett TE
Summary: The Functional Movement Screen (FMS™) is used to identify movement asymmetries and deficiencies. While obesity has been reported to impede movement, the correlation between body mass index (BMI), body fat percentage (BF%), and FMS™ in athletes is unknown. The objective was to determine if there is a relationship between BMI, BF%, and FMS™ scores in a sample of National Collegiate Athletic Association (NCAA) Division I football athletes. 38 male freshman football players (18.0 ± 0.7 y, 185.3 ± 5.5 cm, 103.9 ± 20.3 kg) participated in this study.  Height, weight, and BF% were collected, and subjects underwent the FMS™ conducted by a certified athletic trainer. The dependent variables were BMI, BF%, composite FMS™ score, and seven individual FMS™ test scores. Subjects were grouped as normal BMI (BMI < 30 kg/m2) or obese (BMI ≥ 30 kg/m2). A composite FMS™ score of ≤14 and an individual FMS™ score of ≤1 were classified as cut-offs for poor movement performance. A negative correlation between composite FMS™ score and BMI approached significance (p = 0.07, ρ = -0.296). A negative correlation between composite FMS™ score and BF% was significant (p = 0.010, ρ = -0.449). There was a significant difference in the number of obese subjects scoring below the composite FMS™ cut-off (χ2 = 5.179, p = 0.023) and the individual FMS™ cut-off on the deep squat (χ2 = 6.341, p = 0.012), hurdle step (χ2 = 9.870, p = 0.002), and in-line lunge (χ2 = 5.584, p = 0.018) when compared to normal BMI subjects. Increased BF% and BMI relate to lower composite FMS™ and individual FMS™ test scores, indicating potentially poor movement patterns in larger NCAA football athletes. Future research should focus on examining lower extremity-specific FMS™ tasks individually from composite FMS™ scores.

Mon

21

Aug

2017

Latest research in football - week 32 - 2017

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Conservative Management for Stable High Ankle Injuries in Professional Football Players
Reference: Sports Health. 2017 Jul 1:1941738117720639. doi: 10.1177/1941738117720639. [Epub ahead of print]
Authors: Knapik DM, Trem A, Sheehan J, Salata MJ, Voos JE
Summary: High ankle "syndesmosis" injuries are common in American football players relative to the general population. At the professional level, syndesmotic sprains represent a challenging and unique injury lacking a standardized rehabilitation protocol during conservative management. PubMed, Biosis Preview, SPORTDiscus, PEDro, and EMBASE databases were searched using the terms syndesmotic injuries, American football, conservative management, and rehabilitation. When compared with lateral ankle sprains, syndesmosis injuries result in significantly prolonged recovery times and games lost. For stable syndesmotic injuries, conservative management features a brief period of immobilization and protected weightbearing followed by progressive strengthening exercises and running, and athletes can expect to return to competition in 2 to 6 weeks. Further research investigating the efficacy of dry needling and blood flow restriction therapy is necessary to evaluate the benefit of these techniques in the rehabilitation process. Successful conservative management of stable syndesmotic injuries in professional American football athletes requires a thorough understanding of the anatomy, injury mechanisms, diagnosis, and rehabilitation strategies utilized in elite athletes.


#2 A comprehensive strength testing protocol offers no clinical value in predicting risk of hamstring injury: a prospective cohort study of 413 professional football players
Reference: Br J Sports Med. 2017 Jul 29. pii: bjsports-2017-097754. doi: 10.1136/bjsports-2017-097754. [Epub ahead of print]
Authors: van Dyk N, Bahr R, Burnett AF, Whiteley R, Bakken A, Mosler A, Farooq A, Witvrouw E
Summary: Hamstring injuries remain prevalent across a number of professional sports. In football, the incidence has even increased by 4% per year at the Champions League level over the last decade. The role of muscle strength or strength ratios and their association with risk of hamstring injury remain restricted by small sample sizes and inconclusive results. The purpose of this study is to identify risk factors for hamstring injury in professional football players in an adequately powered, prospective cohort study. Using both established (isokinetic) and novel (eccentric hamstring test device) measures of muscle strength, we aimed to investigate the relationship between these strength characteristics over the entire range of motion with risk of hamstring injury. All teams (n=18) eligible to compete in the premier football league in Qatar underwent a comprehensive strength assessment during their annual periodic health evaluation at Aspetar Orthopaedic and Sports Medicine Hospital in Doha, Qatar. Variables included isokinetic strength, Nordic hamstring exercise strength and dynamic hamstring: quadriceps ratios. Of the 413 players included (68.2% of all league players), 66 suffered a hamstring injury over the two seasons. Only isokinetic quadriceps concentric at 300°/s (adjusted for bodyweight) was associated with risk of hamstring injury when considered categorically. Age, body mass and playing position were also associated with risk of hamstring injury. None of the other 23 strength variables examined were found to be associated with hamstring injury. The clinical value of isolated strength testing is limited, and its use in musculoskeletal screening to predict future hamstring injury is unfounded.


#3 The effects of football match congestion in an international tournament on hip adductor squeeze strength and pain in elite youth players
Reference: J Sports Sci. 2017 Aug 3:1-6. doi: 10.1080/02640414.2017.1363452. [Epub ahead of print]
Authors: Wollin M, Pizzari T, Spagnolo K, Welvaert M, Thorborg K
Summary: The purpose of this study was to investigate the effect of a congested international tournament match schedule on adductor strength and pain in elite youth football players. Twenty-two male players (age: 15.53 ± 0.48 years, height: 174.87 ± 7.59 cm, weight: 67.45 ± 7.40 kg) were included. The 5-second adductor squeeze strength was captured daily using a hand-held dynamometer during a 7-game international tournament. Pain during the squeeze test was recorded using numerical pain ratings (0-10) to quantify groin pain. Sessional rate of perceived exertion (sRPE) was collected during the tournament. Adductor strength changed significantly during the tournament in relation to time (F(14,294.94) = 1.89, p = 0.027) and cumulative sRPE (F(1,314) = 5.59, p = 0.019). Cumulative sRPE displayed a negative relationship with strength (B = -0.008, SE = 0.0032, 95%CI = -0.014,-0.002). The results indicate that for every 100 match sRPE arbitrary units the squeeze peak force reduced by 0.8N. Sixteen (72.7%) players demonstrated clinically meaningful strength reductions (>15%) during the tournament. Match congestion impacts on hip adductor squeeze strength in male youth football players. A negative relationship between match sRPE and adductor strength exists. Player monitoring involving the 5-second adductor squeeze test can be captured effectively and is suitable to include as part of secondary injury prevention during or immediately after a congested tournament.


#4 Response requirements affect offside judgments in football (soccer)
Reference: Psychol Res. 2017 Aug 1. doi: 10.1007/s00426-017-0902-6. [Epub ahead of print]
Authors: Fasold F, Wühr P, Memmert D
Summary: Judging offside in football represents a typical go-nogo task (offside-raising the flag, no offside-no response). Nevertheless, several studies involved two-choice tasks (e.g. offside-press key A, no offside-press key B) to investigate potential sources of errors in offside situations. While go-nogo and choice-response tasks are commonly used in experimental psychology, response preferences may differ between the two tasks. Therefore, we investigated the impact of response requirements on offside judgments in a sample of male participants without experience in professional refereeing. Each participant judged displays of potential offside situations in a go-nogo condition and in a two-choice condition. The results show that response requirements affected the response bias of the participants and suggest that go-nogo requirements increase the preference for the positive response (i.e. the offside response) as compared to the two-choice task. We discuss both methodological and theoretical implications of this finding.


#5 Greenhouse gas emissions as a result of spectators travelling to football in England
Reference: Sci Rep. 2017 Aug 1;7(1):6986. doi: 10.1038/s41598-017-06141-y.
Authors: Dosumu A, Colbeck I, Bragg R
Download link: https://www.nature.com/articles/s41598-017-06141-y.pdf
Summary: Transport remains a critical avenue in the attempt to reduce greenhouse gas (GHG) emissions and any significant effort to reduce travel GHG emissions will need to encourage a movement towards more fuel-efficient, less polluting behaviours. The aim of this paper is to calculate GHG emissions arising from the travel of spectators to and from football games within eight football tiers (3 to 10) in England, and to extrapolate this to a national level. The study comprised of 1649 participants with an average age of 42 years (M = 42.63, SD = 17.10). Participants travelled to and from games by walking, cycling, car, bus, train or taxi. The average distance travelled to and from games was 41.5 km. A Kruskal-Wallis test was conducted to evaluate differences in travel related GHG emissions between the eight football tiers during the 2012/13 season. The results indicate significant differences between football tiers' GHG emissions, H(7) = 46.474, p < 0.001. The annual GHG emission of spectators from the 8 tiers for the 2012/13 season was estimated at 56,237 tonnes of CO2e, accounting for less than 0.05% of transport emissions in England. Football authorities should have robust travel plans and educate spectators to employ more sustainable travel plans to games.


#6 Effects of football sporting activity on renal and liver functions among young undergraduate students of a Nigerian tertiary institution
Reference: BMJ Open Sport Exerc Med. 2017 Jul 11;3(1):e000223. doi: 10.1136/bmjsem-2017-000223. eCollection 2017.
Authors: Ekun OA, Emiabata AF, Abiodun OC, Ogidi NO, Adefolaju FO, Ekun OO
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5530113/pdf/bmjsem-2017-000223.pdf
Summary: Football sporting exercise is one of the most popular events in the world. While there are well-documented reports on the effects of different athletic sporting activities on the biochemical markers of renal and liver functions, there are paucity of well-documented reports on the effects of football activity on Nigerian sportsmen, hence the need for this study. Biochemical markers of renal and liver functions (urea, creatinine, aspartate aminotransaminase (AST), alanine aminotransaminase (ALT), alkaline phosphatase (ALP)) were determined using Cobas c 111 auto-analyser by Roche. The mean urea (mmol/L)±SEM, creatinine (μmol/L)±SEM, AST (U/L)±SEM, ALT (U/L)±SEM and ALP (U/L)±SEM values before and after soccer exercise were 3.56±0.12, 3.76±0.13, p=0.000; 79.36±1.53, 95.90±2.03, p=0.000; 32.54±1.15, 35.81±1.32, p=0.000; 15.68±1.02, 13.97±0.81, p=0.000; and 82.21±3.67, 86.08±3.86, p=0.046, respectively. Pearson's degree of association for AST and ALT before and after exercise were r=0.678, p=0.000 and r=0.770, p=0.000, respectively; ALT and ALP before exercise showed a positive and significant association (r=0.317, p=0.028). On the other hand, there was a negative but insignificant correlation between urea before exercise and ALP after exercise (r=-0.003, p=0.982) and urea before exercise versus AST after exercise (r=-0.120, p=0.418). A positive but insignificant association was observed between urea and creatinine before exercise (r=0.093, p=0.530). Football sporting event is associated with an increase in urea, creatinine, AST and ALP plasma values, and such interpretation of these parameters among sportsmen should be done with caution.


#7 Benign paroxysmal positional vertigo (BPPV) diagnosis and treatment in an elite professional football (soccer) player
Reference: BMJ Case Rep. 2017 Jul 24;2017. pii: bcr-2017-220000. doi: 10.1136/bcr-2017-220000.
Authors: Burrows L, Price R
Summary: A 33-year-old male professional football player suffered from acute-onset dizziness following a lower limb soft tissue treatment in prone lying. Symptoms included spinning vertigo lasting for 30's, headache, visual vertigo and disorientation. Clinical examination of balance and vestibular systems confirmed a left posterior canalithiasis benign paroxysmal positional vertigo (BPPV) and excluded other central and peripheral causes of dizziness. Two cycles of a left Epley manoeuvre were performed. An Epley manoeuvre abolished the BPPV and negated the need for medication. The player was able to return to play without dizziness within 24 hours completely symptom free. BPPV can be successfully identified and treated in elite football players and they can see a return to training and games within 24 hours. There are no epidemiology studies for this group of elite athletes either male or female despite increased occupational risk factors.


#8 Eccentric Training after a Traumatic Apophysis Fracture at the Spina Iliaca Anterior Inferior: Case Study of a Junior Football Player, [Article in German]
Reference: Sportverletz Sportschaden. 2017 Jul 26. doi: 10.1055/s-0043-113209. [Epub ahead of print]
Authors: Landkammer Y, Rieder F, Sassmann R, Herfert J, Wicker A.
Summary: Eccentric training is an established training method in competitive sports. It has been used effectively to improve muscle strength during rehabilitation after cruciate ligament reconstruction. However, it is still uncertain whether or not eccentric training contributes to successful rehabilitation after apophysis fractures. A fourteen-year-old soccer player, forward position, presents with an apophysis avulsion located at the right spina iliaca anterior inferior. After completing an early rehabilitation phase and isokinetic concentric strength development, the patient starts an eccentric training programme eight weeks after the injury, including training on an isokinetic dynamometer (Biodex) for four weeks, followed by a four-week eccentric ergometer training (Eccentron). Before and after each eccentric training phase, isokinetic maximum strength tests of the knee extensors and flexors are performed with angular velocities of 60 degrees per second (°/sec.), 180°/sec. and 240°/sec. In response to the eight-week eccentric rehabilitation program, maximum torque increases in all angular velocities in the injured (60°/sec. + 14.4 %; 180°/sec. + 8.8 %; 240°/sec. + 6.3 %) and the uninjured leg (60°/sec. + 15.6 %; 180°/sec. + 1.9 %; 240°/sec. + 8.1 %) between the first and the last test. Furthermore, neuromuscular coordination has improved during the eccentric training sessions. This case study demonstrates that controlled eccentric training in the open and closed kinetic chain increases coordination and strength of the trained muscles and therefore should be regarded as a valuable contribution toward a safe return to sport after apophysis fractures.


#9 Influence of Match Location, Quality of Opponents, and Match Status on Movement Patterns in Brazilian Professional Football Players
Reference: J Strength Cond Res. 2017 Aug;31(8):2155-2161. doi: 10.1519/JSC.0000000000001674.
Authors: Aquino R, Munhoz Martins GH, Palucci Vieira LH, Menezes RP
Summary: The aim of this study was to examine the independent and interactive effects of match location, quality of opponents, and match status on the movement patterns in a professional Brazilian football team. Sixteen matches of the fourth division Brazilian Championship of 2015 were analyzed during the competitive stages (classifier, 8 matches; octave-finals, 2 matches; quarterfinals, 2 matches; semifinals, 2 matches; and finals, 2 matches). A 5-Hz Global Positioning System Sports QSTARZ was used to record the total distance (TD), maximum speed (VMAX), average speed (VAVERAGE), and frequency of high-intensity activities (HIA). The Student's t-test for independent samples showed significantly higher values (p ≤ 0.05) of VMAX, VAVERAGE, and HIA in home matches when compared with away matches. Comparing the quality of opponents, statistically higher values of TD, VMAX, and HIA were found when the team played against strong opponents. Regarding match status, 1-way analysis of variance demonstrated that when the team won presented significantly higher values of TD, VMAX, VAVERAGE, and HIA compared with matches when the team lost. There were no substantial interactive effects of match situational variables on movement patterns. Finally, multiple linear regression showed that the variable quality of opponents has a higher relative contribution to the variance in HIA (19%) than match status (16%) and match location (4%). In particular, the results indicate that physical performance in professional football is influenced by match situational variables, resulting in a change in the team's style of play.


#10 The Influence of Tactical and Situational Variables on Offensive Sequences during Elite Football Matches
Reference: J Strength Cond Res. 2017 Jul 19. doi: 10.1519/JSC.0000000000002147. [Epub ahead of print]
Authors: Sarmento H, Figueiredo A, Lago-Penas C, Milanovic Z, Barbosa A, Tadeu P, Bradley PS
Summary: This study examined the influence of tactical and situational variables on offensive sequences during elite football matches. A sample of 68 games and 1694 offensive sequences from the Spanish La Liga, Italian Serie A, German Bundesliga, English Premier League and Champions League were analysed using chi-square and logistic regression analyses. Results revealed that counterattacks (OR=1.44; 95% CI: 1.13 to 1.83; P<0.01) and fast attacks (OR=1.43; 95% CI: 1.11 to 1.85; P<0.01) increased the success of an offensive sequence by 40% compared with positional attacks. The chance of an offensive sequence ending effectively in games from the Spanish, Italian and English Leagues were higher than in the Champions League. Offensive sequences that started in the pre-offensive or offensive zones were more successful than those started in the defensive zones. An increase of 1 second in the offensive sequence duration and an extra pass resulted in a decrease of 2% (OR=0.98; 95% CI: 0.98 to 0.99; P<0.001) and 7% (OR=0.93; 95% CI: 0.91 to 0.96; P<0.001), respectively in the probability of its success. These findings could assist coaches in designing specific training situations that improve the effectiveness of the offensive process.


#11 Training and acute exercise modulates mitochondrial dynamics in football players' blood mononuclear cells
Reference: Eur J Appl Physiol. 2017 Jul 26. doi: 10.1007/s00421-017-3684-z. [Epub ahead of print]
Authors: Busquets-Cortes C, Capo X, Martorell M, Tur JA, Sureda A, Pons A
Summary: Regular physical activity induces oxidative stress but also causes adaptations in antioxidant defences including the nuclear factor κB (NF-κB) pathway, which activates target genes related to antioxidant defences such as uncoupling proteins (UCPs), and mitochondrial biogenesis mediated by peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α). The aim of the study was to determine the effect of long-term training and acute exercise on oxidant/antioxidant status and the expression of mitochondrial biogenesis genes in peripheral blood mononuclear cells (PBMCs). Twelve professional football players performed an 8-week exercise programme comprising a daily 2-h football training session. Blood samples were taken before and after the training season. The results reported a significant increase in antioxidant protein levels and in mitochondrial proteins in resting conditions after the 8-week training period. PGC1α, UCP-2 and mitofusin 2 protein levels also increased after acute exercise compared to pre-exercise levels. After the training, the expression of PGC1α, cytochrome c oxidase subunit IV and mitochondrial NADH dehydrogenase subunit 5 messenger RNA (mRNA) significantly augmented after the acute physical activity compared to pre-exercise levels; while no changes occurred in these mRNA in basal conditions. NF-κB activation and ROS production reported a significant increase after acute exercise. Training increases the levels of proteins related to mitochondrial biogenesis and improves the antioxidant capabilities of mitochondria in PBMCs among well-trained football players. Acute exercise may act as an inducer of mitochondrial biogenesis through NF-κB activation and PGC1α gene expression.


#12 Injuries Among Recreational Football Players: Results of a Prospective Cohort Study
Reference: Clin J Sport Med. 2017 Jul 14. doi: 10.1097/JSM.0000000000000425. [Epub ahead of print]
Authors: Donmez G, Korkusuz F, Ozcakar L, Karanfil Y, Dursun E, Kudaş S, Doral MN.
Summary: The purpose was to establish the incidence and patterns of football injuries and associated consequences in daily life and labor loss, among public employees. A total of 1821 recreational players from 78 teams participated in this study. Injury rates (injuries per 1000 hours of football exposure) during tournament by age group, as well as prevalence, severity, and injury types were recorded. The data regarding the occurrence (eg, location, type, circumstances) and consequences (eg, absenteeism, medical treatment, labor loss) of injuries were collected. Of the 1821 football players registered for participation, 57% (n = 1038) were included in the study with the returned questionnaire forms. In total, 257 matches were played with a total exposure time of 5654 hours. A total of 218 injuries were recorded in 192 players (10.5%), resulting in a mean of 0.85 time-loss injuries per match (38.6 per 1000 hours). Severe injuries constituted 42.6% of all injuries, and 28.9% of all injuries caused the participants to be absent at least 1 day for the next working day. The total labor loss was 1196 days for all injuries. The rate of missing subsequent working day was significantly less for muscle injuries (P < 0.05). The risk of injury in recreational football players is relatively high causing significant labor loss. The results suggest that prevention programs should consider specific injury characteristics, as there is a greater incidence of muscle and anterior cruciate ligament injuries in this population.



American Football
#1 Performance and Return to Sport After Achilles Tendon Repair in National Football League Players
Reference: Foot Ankle Int. 2017 Jul 1:1071100717718131. doi: 10.1177/1071100717718131. [Epub ahead of print]
Authors: Jack RA 2nd, Sochacki KR, Gardner SS, McCulloch PC, Lintner DM, Cosculluela PE, Varner KE, Harris JD
Summary: Achilles tendon injuries are common in sports, including football. The purpose of this study was to determine (1) return-to-sport rate in National Football League (NFL) players following Achilles tendon repair, (2) postoperative career length and games per season, (3) pre- and postoperative performance, and (4) postoperative performance compared with control players matched by position, age, years of experience, and performance. Publicly available records were used to identify NFL players who underwent Achilles tendon repair and matched controls were identified. Ninety-five players (98 surgeries) were analyzed (mean age 28.2 ± 2.8 years; mean 5.5 ± 2 .8 years in NFL at time of surgery). Demographic and performance data were collected. Comparisons between case and control groups and preoperative and postoperative time points were made using paired-samples Student t tests. Seventy-one (72.4%) players were able to return to sport in the NFL at a mean of 339.8 ± 84.8 days following surgery. Thirty-one (32%) Achilles tendon repairs were performed during training camp or preseason. Controls (3.6 ± 2.1 years) had a significantly longer NFL career ( P < .05) than players who underwent Achilles tendon repair (2.7 ± 2.1 years). There was no significant difference in games per season in subsequent seasons following surgery compared with controls. Postoperative performance scores were significantly worse ( P < .05) for running backs (RBs) (n = 4) and linebackers (LBs) (n = 12) compared to preoperative scores. LBs had significantly worse postoperative performance scores when compared to matched controls ( P < .05). Following Achilles tendon repair, less than 75% of players returned to the NFL. Postoperative career length was 1 season shorter than matched controls. No difference was observed in the number of games per season played compared to matched controls. Postoperative performance scores were significantly worse for RBs and LBs compared to preoperative and LBs had significantly worse postoperative performance when compared to matched controls.


#2 Clinicopathological Evaluation of Chronic Traumatic Encephalopathy in Players of American Football
Reference: JAMA. 2017 Jul 25;318(4):360-370. doi: 10.1001/jama.2017.8334.
Authors: Mez J, Daneshvar DH, Kiernan PT, Abdolmohammadi B, Alvarez VE, Huber BR, Alosco ML, Solomon TM, Nowinski CJ, McHale L, Cormier KA, Kubilus CA, Martin BM, Murphy L, Baugh CM, Montenigro PH, Chaisson CE, Tripodis Y, Kowall NW, Weuve J, McClean MD, Cantu RC, Goldstein LE, Katz DI, Stern RA, Stein TD, McKee AC
Summary: Players of American football may be at increased risk of long-term neurological conditions, particularly chronic traumatic encephalopathy (CTE). The purpose was to determine the neuropathological and clinical features of deceased football players with CTE. Case series of 202 football players whose brains were donated for research. Neuropathological evaluations and retrospective telephone clinical assessments (including head trauma history) with informants were performed blinded. Online questionnaires ascertained athletic and military history. Participation in American football at any level of play. Neuropathological diagnoses of neurodegenerative diseases, including CTE, based on defined diagnostic criteria; CTE neuropathological severity (stages I to IV or dichotomized into mild [stages I and II] and severe [stages III and IV]); informant-reported athletic history and, for players who died in 2014 or later, clinical presentation, including behavior, mood, and cognitive symptoms and dementia. Among 202 deceased former football players (median age at death, 66 years [interquartile range, 47-76 years]), CTE was neuropathologically diagnosed in 177 players (87%; median age at death, 67 years [interquartile range, 52-77 years]; mean years of football participation, 15.1 [SD, 5.2]), including 0 of 2 pre-high school, 3 of 14 high school (21%), 48 of 53 college (91%), 9 of 14 semiprofessional (64%), 7 of 8 Canadian Football League (88%), and 110 of 111 National Football League (99%) players. Neuropathological severity of CTE was distributed across the highest level of play, with all 3 former high school players having mild pathology and the majority of former college (27 [56%]), semiprofessional (5 [56%]), and professional (101 [86%]) players having severe pathology. Among 27 participants with mild CTE pathology, 26 (96%) had behavioral or mood symptoms or both, 23 (85%) had cognitive symptoms, and 9 (33%) had signs of dementia. Among 84 participants with severe CTE pathology, 75 (89%) had behavioral or mood symptoms or both, 80 (95%) had cognitive symptoms, and 71 (85%) had signs of dementia. In a convenience sample of deceased football players who donated their brains for research, a high proportion had neuropathological evidence of CTE, suggesting that CTE may be related to prior participation in football.


#3 The Influence of Heavier Football Helmet Faceguards on Head Impact Location and Severity
Reference: Clin J Sport Med. 2017 Jul 21. doi: 10.1097/JSM.0000000000000437. [Epub ahead of print]
Authors: Schmidt JD, Phan TT, Courson RW, Reifsteck F 3rd, Merritt ED, Brown CN.
Summary: The purpose was to determine whether players with heavier faceguards have increased odds of sustaining top of the head impacts and head impacts of higher severity. Thirty-five division I collegiate football players participated in this study. Faceguard mass was measured. Head impact location and severity (linear acceleration [gravity], rotational acceleration [radian per square second], and Head Impact Technology severity profile [unitless]) were captured for 19 379 total head impacts at practices using the Head Impact Telemetry System. Players' faceguards were categorized as either heavier (>480 g) or lighter (≤480 g) using a median split. Odds ratios (ORs) and 95% confidence intervals (CIs) were computed for sustaining top of the head impacts between faceguard groups using a random intercepts generalized logit model. We compared head impact severity between groups using random intercepts general linear models (α = 0.05). Player position was included in all models. Overall, the 4 head impact locations were equally distributed across faceguard groups (F(3,26) = 2.16, P = 0.117). Football players with heavier faceguards sustained a higher proportion impacts to the top of the head (24.7% vs 17.5%) and had slightly increased odds of sustaining top (OR, 1.72; 95% CI, 1.01-2.94) head impacts rather than front of the head impacts. Football players wearing heavier faceguards might be slightly more prone to sustaining a higher proportion of top of the head impacts, suggesting that greater faceguard mass may make players more likely to lower their head before collision. Individuals involved with equipment selection should consider the potential influence of faceguard design on head impact biomechanics when recommending the use of a heavier faceguard.


#4 Large case series documents chronic brain damage in players of American football
Reference: BMJ. 2017 Jul 25;358:j3602. doi: 10.1136/bmj.j3602.
Author: McCarthy M

#5 The Role of Neck Muscle Activities on the Risk of Mild Traumatic Brain Injury in American Football
Reference: J Biomech Eng. 2017 Jul 28. doi: 10.1115/1.4037399. [Epub ahead of print]
Authors: Jin X, Feng Z, Mika VH, Li H, Viano D, Yang KH
Summary: Concussion, or mild TBI (mTBI), is frequently associated with sports activities. It has generally been accepted that neck strengthening exercises are effective as a preventive strategy for reducing sports-related concussion risks. However, the interpretation of the link between neck strength and concussion risks remains unclear. In this study, a typical helmeted head-to-head impact in American football was simulated using the head and neck complex finite element model. The impact scenario selected was previously reported in lab-controlled incident reconstructions from high-speed NFL video footages using two head-neck complexes taken from Hybrid III dummies. Four different muscle activation strategies were designed to represent no muscle response, a reactive muscle response, a pre-activation response, and response due to stronger muscle strength. Head kinematics and various head/brain injury risk predictors were selected as response variables to compare the effects of neck muscles on the risk of sustaining the concussion. Simulation results indicated that active responses of neck muscles could effectively reduce the risk of brain injury. Also, anticipatory muscle activation played a dominant role on impact outcomes. Increased neck strength can decrease the time to compress the neck and its effects on reducing brain injury risks need to be further studied.


#7 Sport-related structural brain injury: Three cases of subdural hemorrhage in American high school football
Reference: World Neurosurg. 2017 Jul 20. pii: S1878-8750(17)31172-5. doi: 10.1016/j.wneu.2017.07.072. [Epub ahead of print]
Authors: Yengo-Kahn AM, Gardner RM, Kuhn AW, Solomon GS, Bonfield CM, Zuckerman SL
Summary: The risk of sport-related concussion (SRC) has emerged as a major public health concern. In rare instances, sport-related head injuries can be even more severe, such as subdural hemorrhage, epidural hemorrhage, or malignant cerebral edema. Unlike SRCs, sport-related structural brain injury (SRSBI) is rare, may require neurosurgical intervention, and can lead to permanent neurologic deficit or death. Data characterizing SRSBI is limited and many have recognized the need to better understand these catastrophic brain injuries. The goal of the current series is to describe, in detail, the presentation, management and outcomes of examples of these rare injuries. During the Fall of 2015, three high school football players presented with acute subdural hemorrhages (SDH) following in-game collisions and were treated at our institution within a span of 2 months. For the two athletes who required surgical intervention, a previous SRC was sustained within four weeks prior to the catastrophic event. One year after injury, two players have returned to school, though with persistent deficits. One patient remains non-verbal and wheelchair-bound. None of the athletes has returned to sports. Acute SDH resultant from an in-game football collision is rare. The temporal proximity of the reported SRSBIs to recent SRCs emphasizes the importance of return to play protocols and raises questions regarding the possibility of second impact syndrome. Although epidemiologic conclusions cannot be drawn from this small sample, these cases provide a unique opportunity to demonstrate the presentation, management, and long-term outcomes of SRSBI in American high school football.


#9 Global Positioning System Analysis of a High School Football Scrimmage
Reference: J Strength Cond Res. 2017 Aug;31(8):2183-2188. doi: 10.1519/JSC.0000000000001691.
Authors: Gleason BH, Sams ML, Salley JT, Pustina AA, Stone MH
Summary:  The purpose of this study was to examine the physical demands of a high school American football scrimmage. Male high school football players (N = 25) participated in a spring scrimmage. Global positioning system data and game film were recorded throughout the entirety of the scrimmage to determine the total distance covered, the distance covered in different velocity bands, the number of accelerations and decelerations performed, and the work-to-rest ratio of the scrimmage. The athletes were divided into 2 groups: linemen (L) (N = 7) vs. nonlinemen (NL) (N = 8) for statistical analysis, and independent T-tests with Holm's sequential Bonferroni adjustment were used to determine differences in movement characteristics between the L and NL groups. Average play duration was 5.7 ± 2.1 seconds, whereas the rest interval was 33.4 ± 13.6 seconds between plays, for an overall exercise-to-rest ratio of 1:5.9. Total distance, standing and walking distance, running distance, striding distance, sprinting distance, and total high-speed running distance covered by NL was greater than L (statistically significant at p ≤ 0.05). Distances traveled in each velocity band by position and by play are also included to provide context of our findings. Data from the present study add to the pool of support for the use of position-specific training in preparing high school football players for competition.


#10 No Seasonal Changes in Cognitive Functioning Among High School Football Athletes: Implementation of a Novel Electrophysiological Measure and Standard Clinical Measures
Reference: Clin J Sport Med. 2017 Jul 14. doi: 10.1097/JSM.0000000000000420. [Epub ahead of print]
Authors: Broglio SP, Williams R, Rettmann A, Moore B, Eckner JT, Meehan S.
Summary: The purpose was to evaluate neuroelectric and cognitive function relative to a season of football participation. Cognitive and neuroelectric function declines are hypothesized to be present in football athletes. Seventy-seven high school athletes (15.9 + 0.9 years, 178.6 + 7.2 cm, 74.4 + 14.7 kg, and 0.8 + 0.8 self-reported concussions) participating in football (n = 46) and noncontact sports (n = 31). All athletes completed preseason, midseason, and postseason assessments of cognitive and neuroelectric function, self-reported symptoms, and quality of life. All athletes participated in their respective sports without intervention, while head impact exposure in football athletes was tracked using the Head Impact Telemetry System. Cognitive performance was based on Cogstate computerized cognitive assessment tool processing speed, attention, learning, working memory speed, and working memory accuracy scores. ElMindA brain network activation amplitude, synchronization, timing and connectivity brain network activation scores demarcated neuroelectric performance. Quality of life was assessed on the Health Behavior Inventory and Satisfaction with Life Scale and symptoms on the SCAT3 inventory. Football and control sport athletes did not show declines in cognitive or neuroelectric function, quality-of-life measures, or symptom reports across a season of sport participation. These findings refute the notion that routine football participation places athletes at risk for acute cognitive declines. The lack of impairment may be associated with no association with head impacts and cognitive function, increased physical activity offsetting any declines, and/or test sensitivity. How these findings are associated with long-term cognitive function is unknown.

Tue

08

Aug

2017

Latest research in football - week 31 - 2017

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

 

#1 A Comparison of GPS Workload Demands in Match Play and Small-Sided Games by the Positional Role in Youth Soccer
Reference: J Hum Kinet. 2017 Jun 22;57:129-137. doi: 10.1515/hukin-2017-0054. eCollection 2017 Jun.
Authors: Beenham M, Barron DJ, Fry J, Hurst HH, Figueirdo A, Atkins S
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5504585/pdf/hukin-57-129.pdf
Summary: The external demands of small-sided games (SSGs) according to the positional role are currently unknown. Using a Catapult Minimax X3 5 Hz GPS, with a 100 Hz tri-axial accelerometer, we compared the accumulated tri-axial player workload per min (PLacc·min-1) during friendly youth match play (MP) (11 vs. 11) and SSGs (2 vs. 2, 3 vs. 3, and 4 vs. 4). Significant differences existed between all SSGs and MP for PLacc·min-1 (F = 21.91, p < 0.001, η2 = 0.38), and individual X (F = 27.40, p < 0.001, η2 = 0.43), Y (F = 14.50, p < 0.001, η2 = 0.29) and Z (F = 19.28, p < 0.001, η2 = 0.35) axis loads. Across all conditions, mean PLacc·min-1 was greater for midfielders (p = 0.004, CI: 0.68, 4.56) and forwards (p = 0.037, CI: 0.08, 3.97) than central defenders. In all conditions, greater Y axis values existed for wide defenders (p = 0.024, CI: 0.67, 1.38), midfielders (p = 0.006, CI: 0.18, 1.50) and forwards (p = 0.007, CI: 0.17, 0.15) compared to central defenders. Midfielders reported greater Z axis values compared to central defenders (p = 0.002, CI: 0.40, 2.23). We concluded that SSGs elicited greater external loads than MP, and previous studies may have underestimated the demands of SSGs.


#2 Small-Sided Games in Elite Soccer: Does One Size Fits All?
Reference: Int J Sports Physiol Perform. 2017 Jul 17:1-24. doi: 10.1123/ijspp.2017-0214. [Epub ahead of print]
Authors: Lacome M, Simpson BM, Cholley Y, Lambert P, Buchheit M
Summary: The purpose was to compare the peak intensity of typical Small Sided Games (SSGs) with those of official matches in terms of running demands and mechanical work over different rolling average durations and playing positions. Data were collected in 21 players (25±5 y, 181±7 cm, 77±7 kg) belonging to an elite French football team. SSG data were collected over two seasons during typical training sessions (249 files, 12±4 per player) and official matches (n=12). Players' locomotor activity was recorded using 15-Hz GPS. Total distance (TD, m), high-speed distance (HS, distance above 14.4 km.h-1, m) and mechanical work (MechW, a.u) were analysed during different rolling average periods (1 to 15 min). The SSGs examined were 4v4+Goal Keepers (GKs), 6v6+GKs, 8v8+GKs and 10v10+GKs. Peak TD and HS during 4v4, 6v6 and 8v8 were likely-to-most likely largely lower than during matches (ES: -0.59,±0.38 to -7.36,±1.20). MechW during 4v4 was likely-to-most likely higher than during matches (1-4-min; 0.61±,0.77 to 2.30±,0.64). Relative to their match demands, central defenders (CD) performed more HS than other positions (0.63±,0.81 to 1.61±,0.52) during 6v6. Similarly, central midfielders (CM) performed less MechW than the other positions during 6v6 (0.68,±0.72 to 1.34,±0.99) and 8v8 (0.73,±0.50 to 1.39,±0.32). Peak locomotor intensity can be modulated during SSGs of various formats and durations to either over- or underload match demands, with 4v4 placing the greatest and the least emphasis on MechW and HS, respectively. Additionally, CD and CM tend to be the most and least overloaded during SSGs, respectively.


#3 Importance of physical qualities for speed and change of direction ability in elite female soccer players
Reference: J Strength Cond Res. 2017 Jul 17. doi: 10.1519/JSC.0000000000002114. [Epub ahead of print]
Authors: Emmonds S, Nicholson G, Beggs C, Jones B, Bissas A
Summary: The purpose of this study was to determine the importance of physical qualities for speed and change of direction (CoD) ability in female soccer players. Data were collected on 10 female soccer players who were part of a professional English Women's Super League team. Player assessments included anthropometric (stature and body mass), body composition (dual-energy X-ray absorptiometry), speed (10m, 30m sprint), CoD ability (505 agility), aerobic (Yo-Yo Intermittent Recovery Test), lower-body strength (bilateral knee extensions) and power (countermovement jump [CMJ], squat jump [SJ], 30cm drop jump [DJ]) measures. The relationships between the variables were evaluated using eigenvector analysis and Pearson correlation analysis. Multiple linear regression revealed that the performance variables (10 and 20m speed, mean 505, and CoD deficit mean) can be predicted with almost 100% accuracy (i.e. adjusted R > 0.999) using various combinations of the predictor variables (DJ height, CMJ height, SJ height, lean body mass). An increase of one standard deviation (SD) in DJ height was associated with reductions of -5.636 and -9.082 SD in 10 m and 20 m sprint times. A one SD increase in CMJ also results in a reduction of -3.317 and -0.922 SD respectively in mean 505 and CoD deficit mean values. This study provides comparative data for professional English female soccer players that can be used by strength and conditioning coaches when monitoring player development and assessing the effectiveness of training programmes. Findings highlight the importance of developing reactive strength to improve speed and CoD ability in female soccer players.


#4 Effect of insulin therapy and dietary adjustments on safety and performance during simulated soccer tests in people with type 1 diabetes: study protocol for a randomized controlled trial
Reference: Trials. 2017 Jul 20;18(1):338. doi: 10.1186/s13063-017-2078-1.
Authors: Calvo-Marin J, Torrealba-Acosta G, Campbell M, Gaboury J, Ali A, Chen-Ku CH
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5520333/pdf/13063_2017_Article_2078.pdf
Summary: Despite the reduction in glycemic derangement in patients with type 1 diabetes mellitus (T1D) through dietary and therapeutic adjustments implemented before, during and after continuous exercise, evidence for its effectiveness with intermittent forms of exercise, such as soccer, is still lacking. We designed a study protocol for a randomized, crossover, double-blinded, controlled trial, for the evaluation of the effect that a strategy of dietary and therapeutic modifications may have on safety and performance of persons with T1D in soccer training sessions and cognitive testing. Inclusion criteria comprise: age older than 18 years, more than 2 years since T1D diagnosis, low C-peptide level, a stable insulin regimen, HbA1c less than 9.0% and regular participation in soccer activities. Our primary outcome evaluates safety regarding hypoglycemia events in patients using dietary and therapeutic adjustments, compared with the performance under the implementation of current American Diabetes Association (ADA) usual recommendations for nutritional and pharmacological adjustments for exercise. Additionally, we will evaluate as secondary outcomes: soccer performance, indexed by performance in well-established soccer skill tests, cognitive functions (indexed by Stroop, digital vigilance test (DVT), Corsi block-tapping task (CBP), and rapid visual information processing (RVIP) tests), and glycemic control measured with a continuous glucose monitor (CGM). Dietary and insulin adjustments standardized under a 4-step method strategy have never been tested in a clinical trial setting with intermittent forms of exercise, such as soccer. We hypothesize that through this strategy we will observe better performance by persons with T1D in soccer and cognitive evaluations, and more stable control of glycemic parameters before, during and after exercise execution, indexed by CGM measurements.


#5 Nonoperative Management and Rehabilitation of Osteitis Pubis/Pubic Bone Stress in Professional Soccer Players: A Report of 5 Cases
Reference: J Orthop Sports Phys Ther. 2017 Aug 3:1-20. doi: 10.2519/jospt.2017.7314. [Epub ahead of print]
Authors: McAleer SS, Lippie E, Norman D, Riepenhof H
Summary: Background Pubic bone stress (PBS) is a common acute or chronic response of the pelvis in sports where sprinting, kicking, twisting and cutting are the dominant movements. Little literature exists regarding non-operative rehabilitation strategies for the condition and the outcome of conservative treatment has not been documented. Case Description Five professional and aspiring professional soccer players complaining of pubic symphysis pain, confirmed as PBS on magnetic resonance imaging and objective assessment. All cases followed a non-operative rehabilitation program, featuring functional and clinical objective markers as progression criteria. Acute interventions included pharmacological and physical therapeutic modalities to reduce pain initially. Rehabilitation management focused on improving range of motion ant the hips and thorax, adductor strengthening, trunk and lumbopelvic stability, gym-based strength training and field-based rehabilitation and conditioning. Clinical follow-up was performed at least 8 months following return to play. Outcomes All players demonstrated reduced or resolved pain, increased adductor squeeze strength, and return to pain free training and match-play. Return to training time averaged 40.6 days (range, 30-60) and return to play averaged 49.4 days (range, 38-72) within the 5 players. At final follow up (mean = 29.6 months, range, 16-33) there had been no recurrences. Discussion This case series suggests a non-operative pathway, using clinical and functional progression criteria is a successful protocol in rehabilitating athletes with PBS in returning to sport within 11 weeks.


#6 Activity profiles in U17, U20 and senior women's Brazilian National soccer teams during international competitions: Are there meaningful differences?
Reference: J Strength Cond Res. 2017 Jul 31. doi: 10.1519/JSC.0000000000002170. [Epub ahead of print]
Authors: Ramos GP, Nakamura FY, Penna EM, Wilke CF, Pereira LA, Loturco I, Capelli L, Mahseredjian F, Silami-Garcia E, Coimbra CC.
Summary: The aim of this study was to compare locomotor activity profiles of Brazilian top-class female soccer players competing at distinct age brackets (U17, U20, and Senior). External match load of 14 U17, 14 U20, and 17 Senior female soccer players competing in 6-7 full official international matches were assessed using global positioning systems (GPS). Total distance covered, distance covered in high intensity (HID:15.6-20 kmh), distance covered in sprints (sprint:>20 kmh), number of accelerations (Acc)>1 ms, decelerations (Dec) >-1 ms, and Player Load generally increased across the age brackets (U17<U20<Senior). For all playing positions, Senior athletes presented greater total distance, accelerations, and decelerations than U20 players. For high-intensity distance and sprints, only central defender and midfielder senior players presented greater values than U20 players. Senior players demonstrated higher values in all locomotor activities in comparison to U17 players, irrespective of playing positions. Except for central defenders that presented similar total distance, sprint distance, and number of accelerations between U20 and U17, the majority of match external loads evaluated in all playing positions were greater in U20 than in U17 players. These results provide useful information for player development and should be used to establish appropriate match-specific conditioning drills according to age categories.


#7 Response requirements affect offside judgments in football (soccer)
Reference: Psychol Res. 2017 Aug 1. doi: 10.1007/s00426-017-0902-6. [Epub ahead of print]
Authors: Fasold F, Wuhr P, Memmert D
Summary: Judging offside in football represents a typical go-nogo task (offside-raising the flag, no offside-no response). Nevertheless, several studies involved two-choice tasks (e.g. offside-press key A, no offside-press key B) to investigate potential sources of errors in offside situations. While go-nogo and choice-response tasks are commonly used in experimental psychology, response preferences may differ between the two tasks. Therefore, we investigated the impact of response requirements on offside judgments in a sample of male participants without experience in professional refereeing. Each participant judged displays of potential offside situations in a go-nogo condition and in a two-choice condition. The results show that response requirements affected the response bias of the participants and suggest that go-nogo requirements increase the preference for the positive response (i.e. the offside response) as compared to the two-choice task. We discuss both methodological and theoretical implications of this finding.


#8 Static stretching does not enhance recovery in elite youth soccer players
Reference: BMJ Open Sport Exerc Med. 2017 Apr 22;3(1):e000202. doi: 10.1136/bmjsem-2016-000202. eCollection 2017.
Authors: Pooley S, Spendiff O, Allen M, Moir HJ
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5530097/pdf/bmjsem-2016-000202.pdf
Summary: Static stretching (SS) is a recovery intervention used for the reduction of muscle soreness postexercise. The effects of SS on elite young footballers have received little attention, and therefore the aim of this study was to assess the effects of SS on muscle recovery following competitive soccer matches in elite young footballers. Ten male participants (16±1 years) were recruited from an English Premier League professional soccer academy. Using a controlled crossover design, participants followed one of two recovery interventions (SS or passive recovery (PR)) immediately following completion of competitive soccer matches. Muscle oedema, creatine kinase (CK), countermovement jump with arms (CMJA) performance and perceived muscle soreness were assessed before, immediately after and 48 hours postmatch. Competitive soccer matches significantly induced muscle damage, with time intervals of perceived soreness and CK showing significant increases (p<0.05), and CMJA showing significant decreases between prematch, postmatch and 48 hours postmatch for both SS and PR (p<0.05). Comparisons of the absolute effects of SS with PR only revealed significant decreases for CK 48 hours postmatch (p<0.05) as a result of SS intervention. The current study demonstrated competitive soccer matches induced muscle damage, which may have detrimental effects on future performance within 24-48 hours postmatch. Furthermore, there was limited evidence to suggest SS would assist in the reduction of muscle soreness postexercise. Therefore, it can be argued that SS is not a beneficial recovery option for elite youth soccer players.


#9 Maturity status influences the relative age effect in national top level youth alpine ski racing and soccer
Reference: PLoS One. 2017 Jul 31;12(7):e0181810. doi: 10.1371/journal.pone.0181810. eCollection 2017.
Authors: Muller L, Gonaus C, Perner C, Muller E, Raschner C
Download link: http://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0181810&type=printable
Summary: Since the relative age effect (RAE) characterizes a problem in all age categories of alpine ski racing and soccer and the fact that, yet, to date the underlying factors have not been well investigated, the aim of the present study was to assess the influence of the biological maturity status on the RAE among youth alpine ski racers (YSR) and soccer players (SP). In total, 183 male and female YSR selected for national final races and 423 male SP selected for Elite Youth Development Centres were investigated. Additionally, a comparison group of 413 non-athletes was evaluated. The birth months were split into four relative age quarters. The biological maturity status was assessed by the age at peak height velocity (APHV) method; according to the M±SD of the comparison group, the athletes were divided into normal, early and late maturing. Chi2-tests indicated a significant RAE among YSR (χ2(3,N = 183) = 18.0; p<0.001; ω = 0.31) and SP (χ2(3,N = 423) = 33.1; p<0.001; ω = 0.28). In total, only a small number of late maturing athletes were present (0.5-2.3%). Among relatively younger athletes, high percentages of early maturing athletes were found (43.1-43.3%). The findings indicate that relatively younger and less mature athletes are marginalized or totally excluded in alpine ski racing and soccer. Thus, selection criteria in both sports are effectively based on early biological development and relatively older age, both of which should be considered in future in the talent selection process. In this context, the easy feasible method of assessing the APHV can be used.


#10 The isokinetic strength profile of elite soccer players according to playing position
Reference: PLoS One. 2017 Jul 31;12(7):e0182177. doi: 10.1371/journal.pone.0182177. eCollection 2017.
Authors: Sliwowski R, Grygorowicz M, Hojszyk R, Jadczak L
Download link: http://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0182177&type=printable
Summary: The aim of this study was to compare isokinetic strength performance profiles in elite soccer players across different field positions. A total of 111 elite international players of Polish Ekstraklasa (the top division in Poland) were examined during the 2010-2015 seasons. The players were classified into six positional roles: central defenders (CD), external defenders (ED), central midfielders (CM), external midfielders (EM), forwards (F), and goalkeepers (G). The concentric isokinetic strength (peak torque [PT] of quadriceps and hamstrings, H/Q ratios) was calculated for the dominant leg and the non-dominant leg at angular velocity of 1.05 rad ·s-1, whereas to assess isokinetic muscle endurance, the total work [TW] at angular velocity of 4.19 rad ·s-1, was taken into consideration. The results showed that isokinetic strength performance varies significantly among players in different playing positions. The analysis of PT for quadriceps (PT-Q) and hamstrings (PT-H) generally showed that the goalkeepers and central midfielders had lower strength levels compared to other playing positions. In the case of PT-H and hamstring/quadricep (H/Q) peak torque ratios, statistically significant differences were also noted for the legs, where mean values noted for the dominant leg were higher than for the non-dominant leg. For TW for quadriceps (TW-Q) and hamstrings (TW-H), statistically significant differences were noted only between playing positions. TW-Q values for goalkeepers were lower than for central defenders and external midfielders. TW-H values for goalkeepers were lower than for central midfielders, central defenders and external midfielders. This study showed that specific functional activity of players in individual positions on the field influences the varied profile of isokinetic strength performance.


#11 Reliability characteristics and applicability of a repeated sprint ability test in male young soccer players
Reference: J Strength Cond Res. 2017 Jul 28. doi: 10.1519/JSC.0000000000002031. [Epub ahead of print]
Authors: Castagna C, Francini L, Krustrup P, Fenarnandes-da-Silva J, Povoas SCA, Bernardini A, D'Ottavio S.
Summary: The aim of this study was to examine the usefulness and reliability characteristics of a repeated sprint ability test considering 5 line sprints of 30-m interspersed with 30-s of active recovery in non-elite outfield young male soccer players. Twenty-six (age 14.9±1.2 years, height 1.72±0.12 cm, body mass 62.2±5.1 kg) players were tested 48 hours and 7 days apart for 5x30-m performance over 5 trials (T1-T5). Short- (T1-T2) and long-term reliability (T1-T3-T4-T5) were assessed with Intraclass Correlation Coefficient (ICC) and with typical error for measurement (TEM). Short- and long-term reliability ICCs and TEMs for total sprint time and best sprint performance were nearly perfect and satisfactory, respectively. Usefulness (as smallest worthwhile change and TEM ratio) resulted acceptable (i.e =1) and good (i.e >1) for total sprint time and best sprint performance, respectively. The present study revealed that the 5x30-m sprint test is a reliable field test in the short and long-term when the sum of sprint times and the best sprint performance are considered as outcome variables. Sprint performance decrements variables showed large variability across trials.


#12 MRI detection of soleus muscle injuries in professional football players
Reference: Skeletal Radiol. 2017 Aug 2. doi: 10.1007/s00256-017-2729-z. [Epub ahead of print]
Authors: Pezzotta G, Querques G, Pecorelli A, Nani R, Sironi S
Summary: The purpose was to describe magnetic resonance imaging (MRI) characteristics of soleus muscle injuries in symptomatic professional football players stratified according to both the Munich consensus statement and the British Athletics Muscle Injury Classification (BAMIC), and to investigate the association between specific MRI features and the "return to play" (RTP). Professional football players with an episode of acute posterior calf pain and impaired function, subsequent to sports activity, underwent ultrasound followed by MRI examination reviewed by two different radiologists with more than 10 years of experience in the musculoskeletal system. MRI features and RTP outcome were evaluated for all types of injuries. During a 36-month period, a total of 20 professional football players were evaluated. According to the Munich consensus, 11 were type 3A, 8 were type 3B, and 1 was type 4, whereas according to the BAMIC, 11 lesions were considered grade 1, 4 grade 2, 4 grade 3, and 1 grade 4. RTP data were available for all patients (mean 3.3 ± 1.6 weeks). Both the Munich consensus and the BAMIC correlated with RTP (Spearman correlation = 0.982 and p < 0.0001 and 0.886 and p < 0.0001 respectively). Extension of edema was an independent prognostic factor for RTP in two different models of multivariate regression analysis (p = 0.044 model A; p = 0.031 model B). The Munich consensus and BAMIC grading systems are useful tools for defining the patient's prognosis and proper rehabilitation time after injury. The MRI feature that we should carefully look for is the extension of edema, as it seems to significantly affect the RTP.


#13 Possession Zone as a Performance Indicator in Football. The Game of the Best Teams
Reference: Front Psychol. 2017 Jul 14;8:1176. doi: 10.3389/fpsyg.2017.01176. eCollection 2017.
Authors: Casal CA, Maneiro R, Arda T, Mari FJ, Losada JL
Summary: Possession time in football has been widely discussed in research but few studies have analyzed the importance of the field area in which possession occurs. The objective of this study was to identify the existence of significant differences in the field zone of ball possession between successful and unsuccessful teams and to acknowledge if the match status modulates the possession model. To this end, 2,284 attacks were analyzed corresponding to the matches in the final phase of the UEFA Euro 2016 France, recording possession time and field zone in which possession occurred. Video recordings of matches were analyzed and coded post-event using notational analysis. We have found that successful offensive game patterns are different from unsuccessful ones. Specifically, field zone in which major possession occurs changes significantly between successful and unsuccessful teams (x2 = 15.72, p < 0.05) and through Welch's T significant differences were detected in possession time between successful and unsuccessful teams (H = 24.289, p < 0.001). The former are characterized by longer possession times, preferably in the middle offensive zone, on the other hand, unsuccessful teams have shorter possession times and preferably on the middle defensive zone. Logistic regression also allowed us to identify that greater possession in the middle offensive zone is a good indicator of success in the offensive game, allowing us to predict a greater chance of victory in the match. Specifically, every time the teams achieve possession in the middle offensive zone, the chance of winning the match will increase 1.72 times and, the probability of winning the match making longer possessions in the middle offensive zone is 44.25%. Applying the Kruskal-Wallis test we have also been able to verify how match status modulates the teams possession time, specifically, when teams are winning they have longer possessions x2 = 92.628, p = 0.011. Results obtained are expected to help gain more knowledge about successful offensive game models, as well as performance factors of the offensive phase, which will allow teams to optimize their training process and performance during the match.


American Football
#1 CPR performance in the presence of audiovisual feedback or football shoulder pads
Reference: BMJ Open Sport Exerc Med. 2017 Jul 24;3(1):e000208. doi: 10.1136/bmjsem-2016-000208. eCollection 2017.
Authors: Tanaka S, Rodrigues W, Sotir S, Sagisaka R, Tanaka H
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5530121/pdf/bmjsem-2016-000208.pdf
Summary: The initiation of cardiopulmonary resuscitation (CPR) can be complicated by the use of protective equipment in contact sports, and the rate of success in resuscitating the patient depends on the time from incident to start of CPR. The aim of our study was to see if (1) previous training, (2) the presence of audiovisual feedback and (3) the presence of football shoulder pads (FSP) affected the quality of chest compressions. Six basic life support certified athletic training students (BLS-ATS), six basic life support certified emergency medical service personnel (BLS-EMS) and six advanced cardiac life support certified emergency medical service personnel (ACLS-EMS) participated in a crossover manikin study. A quasi-experimental repeated measures design was used to measure the chest compression depth (cm), rate (cpm), depth accuracy (%) and rate accuracy (%) on four different conditions by using feedback and/or FSP. Real CPR Help manufactured by ZOLL (Chelmsford, Massachusetts, USA) was used for the audiovisual feedback. Three participants from each group performed 2 min of chest compressions at baseline first, followed by compressions with FSP, with feedback and with both FSP and feedback (FSP+feedback). The other three participants from each group performed compressions at baseline first, followed by compressions with FSP+feedback, feedback and FSP. CPR performance did not differ between the groups at baseline (median (IQR), BLS-ATS: 5.0 (4.4-6.1) cm, 114(96-131) cpm; BLS-EMS: 5.4 (4.1-6.4) cm, 112(99-131) cpm; ACLS-EMS: 6.4 (5.7-6.7) cm, 138(113-140) cpm; depth p=0.10, rate p=0.37). A statistically significant difference in the percentage of depth accuracy was found with feedback (median (IQR), 13.8 (0.9-49.2)% vs 69.6 (32.3-85.8)%; p=0.0002). The rate accuracy was changed from 17.1 (0-80.7)% without feedback to 59.2 (17.3-74.3)% with feedback (p=0.50). The use of feedback was effective for depth accuracy, especially in the BLS-ATS group, regardless of the presence of FSP (median (IQR), 22.0 (7.3-36.2)% vs 71.3 (35.4-86.5)%; p=0.0002). The use of audiovisual feedback positively affects the quality of the depth of CPR. Both feedback and FSP do not alter the rate measurements. Medically trained personnel are able to deliver the desired depth regardless of the presence of FSP even though shallower chest compressions depth can be seen in CPR with FSP. A feedback device must be introduced into the athletic training settings.


#2 A comparison of the technique of the football quarterback pass between high school and university athletes
Reference: J Strength Cond Res. 2017 Jul 28. doi: 10.1519/JSC.0000000000002068. [Epub ahead of print]
Authors: Toffan A, Alexander MJL, Peeler J
Summary: The purpose of the study was to compare the most effective joint movements, segment velocities and body positions to perform the fastest and most accurate pass of high school and university football quarterbacks. Secondary purposes were to develop a quarterback throwing test to assess skill level, to determine which kinematic variables were different between high school and university athletes as well as to determine which variables were significant predictors of quarterback throwing test performance. Ten high school and ten university athletes were filmed for the study, performing nine passes at a target and two passes for maximum distance. Thirty variables were measured using Dartfish Team Pro 4.5.2 video analysis system, and Microsoft Excel was used for statistical analysis. University athletes scored slightly higher than the high school athletes on the throwing test, however this result was not statistically significant. Correlation analysis and forward stepwise multiple regression analysis was performed on both the high school players and the university players in order to determine which variables were significant predictors of throwing test score. Ball velocity was determined to have the strongest predictive effect on throwing test score (r = 0.900) for the high school athletes, however, position of the back foot at release was also determined to be important (r = 0.661) for the university group. Several significant differences in throwing technique between groups were noted during the pass, however, body position at release showed the greatest differences between the two groups. High school players could benefit from more complete weight transfer and decreased throw time to increase throwing test score. University athletes could benefit from increased throw time and greater range of motion in external shoulder rotation and trunk rotation to increase their throwing test score. Coaches and practitioners will be able to use the findings of this research to help improve these and related throwing variables in their high school and university quarterbacks.


#3 A Comparison of Pre-Season and In-Season Practice and Game Loads in NCAA Division I Football Players
Reference: J Strength Cond Res. 2017 Jul 31. doi: 10.1519/JSC.0000000000002173. [Epub ahead of print]
Authors: Wellman AD, Coad SC, Flynn PJ, Siam TK, McLellan CP
Summary: The aim of the present study was to quantify the individual practice and game loads throughout an NCAA division I football season to determine if significant differences exist between the practice loads associated with pre-season training camp and those undertaken during the in-season period. Thirty-one NCAA division I football players were monitored using GPS and IA (MinimaxX S5; Catapult Innovations, Melbourne, Australia) during 22 pre-season practices, 36 in-season practices, and 12 competitions. The season was divided into four distinct phases for data analysis: pre-season week 1 (pre-season1), pre-season week 2 (pre-season2), pre-season week 3 (pre-season3), and 12 in-season weeks. Individual IA datasets represented players from every offensive and defensive position group (WR: n=5), (OL: n=4), (RB: n=4), (QB: n=2), (TE: n=3), (DL: n=4), (LB: n=4), (DB: n=5). Data were set at the practice level, where an observation for each player's maximum player load (PLMax) or mean player load (PLMean) from each training camp phase was referenced against each player's respective PL from each game, Tuesday, Wednesday, or Thursday practice session. Notable results included significantly (p<0.05) greater PLMax values attributed to pre-season1 compared to PL resulting from all in-season practices, and significantly (p<0.05) higher cumulative PL reported for pre-season1, 2, and 3 compared to every in-season week. Data from the present study augment our understanding of the practice demands experienced by NCAA division I college football players, and provide scope for the improvement of pre-season practice design and physical conditioning strategies for coaches seeking to optimize performance.


#4 Performance and Return to Sport After Nonoperative Treatment of Clavicle Fractures in National Football League Players
Reference: Orthopedics. 2017 Aug 3:1-8. doi: 10.3928/01477447-20170719-03. [Epub ahead of print]
Authors: Jack RA 2nd, Sochacki KR, Navarro SM, McCulloch PC, Lintner DM, Harris JD.
Summary: Clavicle fractures are often seen in contact sports. The purpose of this study was to determine (1) return-to-sport (RTS) rate of National Football League (NFL) players following nonoperative treatment of clavicle fractures, (2) posttreatment career length and games per season, (3) pre- and posttreatment performance, and (4) posttreatment performance compared with control players matched by position, age, years of experience, and performance. Public records were used to identify NFL players who underwent nonoperative treatment of clavicle fractures. Demographic and performance data were collected for each player. Matched controls (position, age, experience, and performance) were identified. Control and case performance scores were calculated using a standardized scoring system. Return to sport was defined as playing a minimum of 1 game after treatment. Comparisons between the 2 groups and pre- and posttreatment time points were made using paired-samples Student's t tests. Thirty players (32 fractures) were analyzed. Two players fractured their contralateral clavicle. Of the players analyzed, 96.9% were able to RTS at a mean of 244.6±119.6 days. Eight players (27.6%) returned within the same season as their injury. Overall 1-year survival rate posttreatment was 93.5%. Players with nonoperative treatment had career lengths similar to those of controls (P>.05). No significant (P>.05) differences existed in demographic, performance, or games per season data between position groups for cases and matched controls pretreatment and preindex and in posttreatment compared with pretreatment performance scores. Wide receivers played fewer games per season (P=.043) following treatment. No position group had significantly worse posttreatment performance scores when compared with postindex matched controls.


Australian Football
#1 Inter- and intra-rater reliability of the Athletic Ability Assessment in sub-elite Australian Rules football players
Reference: J Strength Cond Res. 2017 Jul 31. doi: 10.1519/JSC.0000000000002175. [Epub ahead of print]
Authors: Rogers DK, McKeown I, Parfitt G, Burgess D, Eston RG.
Summary: The aim of this study was to determine the inter- and intra-rater rater reliability of the Athletic Ability Assessment (AAA) in sub-elite Australian Rules football (ARF) players. Eighteen male ARF players completed the AAA movement assessment (overhead squat, double lunge [left and right], single leg Romanian deadlift [left and right], chin-up and push-up), on two occasions separated by one week. During the first movement assessment players were filmed in the frontal and sagittal planes. Ten raters took part in the study (one experienced rater and nine novices) and were assigned in a quasi-random manner, to complete either (a) real-time assessment on two occasions, (b) real-time assessment on one occasion or (c) video-based assessment on two occasions. When assessed in real-time, of the 7 component movements of the AAA, raters registered moderate or greater intra-rater agreement on between 2 and 5 occasions. Intraclass correlation coefficients (ICC) of between 0.50 and 0.61 for the AAA total score indicated poor real-time intra-rater reliability for this variable. When assessed by video-recording, raters registered moderate or greater intra-rater agreement on between 6 and 7 occasions. The ICC for total score ranged between 0.60 and 0.93. Overall poor inter-rater reliability was evident for AAA component movements regardless of whether it was assessed in real-time or from video. Findings suggest the AAA is most reliably employed when assessed via video. It is recommended that if comparison between multiple raters is desired, a stringent training process be applied so that the interpretation of AAA scoring criteria is standardised across raters.


#2 Concussion guideline implementation perceptions and experiences among parents of community-level Australian Football junior players
Reference: BMJ Open Sport Exerc Med. 2017 Apr 22;3(1):e000215. doi: 10.1136/bmjsem-2016-000215. eCollection 2017.
Authors: White PE, Register-Mihalik J, Donaldson A, Sullivan SJ, Finch CF
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5530102/pdf/bmjsem-2016-000215.pdf
Summary: Concussion guidelines exist for multiple community sports. Parents are key stakeholders in guideline implementation and in appropriate responses following concussive injury. The purpose of this qualitative investigation was to understand how parents of community-level Australian Football (AF) players experience and perceive concussion guidelines in order to inform the design and implementation of concussion guidelines in community sport. A cross-sectional qualitative approach was adopted to allow for an open and detailed exploration of the views of parents of junior community AF players (ie, those aged <16 years) regarding concussion guidelines of the AF League (AFL)-the national governing body for AF. Participants were 15 parents of junior community AF players from two clubs affiliated with a large regional community AF League. The key experiences and perceptions of the parents included appreciation that the guidelines outlined the postconcussion process that should be followed, desires for better understanding of the guidelines by general practitioners (ie, medical doctors) who care for children with concussion, having more readily available information for parents and receiving more formal policy guiding timing of return-to-participation following concussion. Difficulties with the guidelines not addressing delayed presentations of concussion were also frequently mentioned. Parents are key stakeholders in concussion prevention and care in community sport. As such, their input should be considered when developing guidelines and resources for community sport. Furthermore, concussion information should be made available to parents in an easily accessible and community-friendly form.

Mon

07

Aug

2017

Latest research in football - week 30 - 2017

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 The preventive effect of a soccer-specific ankle brace on acute lateral ankle sprains in girls amateur soccer players: study protocol of a cluster-randomised controlled trial
Reference: Inj Prev. 2017 Jul 27. pii: injuryprev-2017-042465. doi: 10.1136/injuryprev-2017-042465. [Epub ahead of print]
Authors: Thijs K, Huisstede B, Goedhart E, Backx F
Summary: Acute lateral ankle sprains are the single most often diagnosed injury in female soccer players and often result in an inability to play. This highlights the need for effective prevention strategies. Proprioceptive training and/or the use of an external support to decrease inversion of the ankle joint can prevent or reduce the number of acute lateral ankle sprains. The effectiveness of a soccer-specific ankle brace in reducing first-time and recurrent acute lateral ankle sprains has never been investigated in girl soccer players. If effective, ankle braces could be introduced into soccer. Girl amateur soccer players (aged 14-18 years) will be allocated to an intervention or control group. The intervention group will be instructed to wear soccer-specific ankle braces on both ankles during soccer training and matches; the control group will continue playing soccer as usual. Primary outcomes are the incidence and severity of acute lateral ankle sprains. Secondary outcomes are the prognostic value of generalised joint hypermobility and functional stability on the risk of acute lateral ankle sprains and compliance with the intervention. The findings from this study may provide evidence to support the use of a soccer-specific ankle brace to prevent lateral ankle sprains during soccer. We hypothesise that this brace will reduce the incidence of ankle sprains among young amateur girl soccer players by 50%. The prevention of such injuries will be beneficial to players, clubs and society.


#2 The use of metabolic power to assess physical demands in soccer: how does it differ from the traditional approach through speed running?
Reference: J Sports Med Phys Fitness. 2017 Jul 25. doi: 10.23736/S0022-4707.17.07563-6. [Epub ahead of print]
Authors: Martinez-Cabrera FI, Nunez-Sanchez FJ
Summary: Metabolic power and speed running are in the top-10-ranked variables used to quantify the physical demand in soccer matches or training practices. The purpose of this study were 1) to compare metabolic power (MP) and the traditional approach using speed running during soccer matches in absolute values and 2) in zones of intensity in function of the playing positions. Thirty-eight professional soccer players were analysed during 18 friendly matches from 4 preseasons (n=300) and divided into 5 groups of playing positions: central defender (CD) (n=64), wide defender (WD) (n=55), central midfielder (CM) (n=58), wide attacker (WA) (n=70) and attacker (AT) (n=53). The individual profiles to each playing positions were assessed using MP and speed running approaches. The magnitude of change was substantial when there was a ≥75% likelihood of the effect. The effect size was also calculated using a confidence interval of 90%. In absolute values, CMs and WAs had substantially greater values than did the other positions, with CMs having the highest values in both approaches and an identical relationship between the positions in both approaches. In categories of intensity, medium-low intensity displayed differences between the approaches; the physical demands of ATs and CDs were lower using the traditional approach but were higher than the other playing positions when assessed using MP. No differences were found at low, medium or high intensities. The MP and energy expenditure reported differences at medium-low intensity compared to the speed running traditional approach between playing positions. However, the other intensities did not report differences compared to the traditional approach in the different playing positions.


#3 The relationship between movement speed and duration during soccer matches
Reference: PLoS One. 2017 Jul 25;12(7):e0181781. doi: 10.1371/journal.pone.0181781. eCollection 2017.
Authors: Roecker K, Mahler H, Heyde C, Roll M, Gollhofer A
Download link: http://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0181781&type=printable
Summary: The relationship between the time duration of movement (t(dur)) and related maximum possible power output has been studied and modeled under many conditions. Inspired by the so-called power profiles known for discontinuous endurance sports like cycling, and the critical power concept of Monod and Scherrer, the aim of this study was to evaluate the numerical characteristics of the function between maximum horizontal movement velocity (HSpeed) and t(dur) in soccer. To evaluate this relationship, GPS data from 38 healthy soccer players and 82 game participations (≥30 min active playtime) were used to select maximum HSpeed for 21 distinct t(dur) values (between 0.3 s and 2,700 s) based on moving medians with an incremental t(dur) window-size. As a result, the relationship between HSpeed and Log(t(dur)) appeared reproducibly as a sigmoidal decay function, and could be fitted to a five-parameter equation with upper and lower asymptotes, and an inflection point, power and decrease rate. Thus, the first three parameters described individual characteristics if evaluated using mixed-model analysis. This study shows for the first time the general numerical relationship between t(dur) and HSpeed in soccer games. In contrast to former descriptions that have evaluated speed against power, HSpeed against t(dur) always yields a sigmoidal shape with a new upper asymptote. The evaluated curve fit potentially describes the maximum moving speed of individual players during the game, and allows for concise interpretations of the functional state of team sports athletes.


#4 Relevance of whole body virabtion exercise in sport: A short review with soccer, diver and combat sport
Reference: Afr J Tradit Complement Altern Med. 2017 Jul 7;14(4 Suppl):19-27. doi: 10.21010/ajtcam.v14i4S.3. eCollection 2017.
Authors: Morel DS, Dionello CDF, Moreira-Marconi E, Brandao-Sobrinho-Neto S, Paineiras-Domingos LL, Souza PL, Sa-Caputo DDC, Dias G, Figueiredo C, Carmo RCR, Paiva PC, Sousa-Goncalves CR, Kutter CR, Guedes-Aguiar EO, Cloak R, Bernardo-Filho M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5514442/pdf/AJTCAM-14-19.pdf
Summary: Whole body vibration exercise (WBVE) has been used as a safe and accessible exercise and important reviews have been published about the use of this exercise to manage diseases and to improve physical conditions of athletes The aim of this paper is to highlight the relevance of WBVE to soccer players, divers and combat athletes. This study was made through a systematic review of publications involving WBVE and the selected sports in two databases (Pubmed and PEDRo). It were identified 10 studies involving WBVE and sports (6 of soccer, 2 of diving and 2 of sport combat) with 156 subjects (80 soccer players, 32 divers and 44 combat athletes), with age from 17 to 44 years old. The use of WBVE has proven to be a safe and useful strategy to improve the physical conditions of players of different sports. These findings may have clinical relevance and should be considered as a strategy to be used to try improve the physical conditions of players.


#5 Benign paroxysmal positional vertigo (BPPV) diagnosis and treatment in an elite professional football (soccer) player
Reference: BMJ Case Rep. 2017 Jul 24;2017. pii: bcr-2017-220000. doi: 10.1136/bcr-2017-220000.
Authors: Burrows L, Price R
Summary: A 33-year-old male professional football player suffered from acute-onset dizziness following a lower limb soft tissue treatment in prone lying. Symptoms included spinning vertigo lasting for 30's, headache, visual vertigo and disorientation. Clinical examination of balance and vestibular systems confirmed a left posterior canalithiasis benign paroxysmal positional vertigo (BPPV) and excluded other central and peripheral causes of dizziness. Two cycles of a left Epley manoeuvre were performed. An Epley manoeuvre abolished the BPPV and negated the need for medication. The player was able to return to play without dizziness within 24 hours completely symptom free. BPPV can be successfully identified and treated in elite football players and they can see a return to training and games within 24 hours. There are no epidemiology studies for this group of elite athletes either male or female despite increased occupational risk factors.


#6 Opportunities and Benefits for Powerchair Users Through Power Soccer
Reference: Adapt Phys Activ Q. 2017 Jul;34(3):235-255. doi: 10.1123/apaq.2016-0022.
Authors: Jeffress MS, Brown WJ
Summary: Power soccer (or powerchair football), the first competitive team sport for users of motorized wheelchairs, is receiving increased attention among people with disabilities, healthcare professionals, and academics. The present study provides a qualitative analysis of the experiences of 34 American power soccer athletes. Participant observation and in-depth interviews with 11 female and 23 male athletes were conducted between 2007 and 2013. Results indicate that involvement in power soccer provides participants with an increased sense of empowerment, acquisition of social capital, and psychosocial benefits, including a deep satisfaction of the desire to participate in competitive sports and an opportunity to be independent. Implications of these findings for improving the quality of life of people with physical disabilities and for future research are discussed.


#7 Biomechanical differences in female basketball and soccer players during multi-directional jump landings
Reference: J Strength Cond Res. 2017 Jul 14. doi: 10.1519/JSC.0000000000001785. [Epub ahead of print]
Authors: Taylor JB, Ford KR, Schmitz RJ, Ross SE, Ackerman TA, Shultz SJ.
Summary: Anterior cruciate ligament injury prevention programs are less successful in basketball than soccer and may be due to distinct movement strategies that these athletes develop from sport-specific training. The purpose of this study was to identify biomechanical differences between female basketball and soccer players during multi-directional jump landings. Lower extremity biomechanics of eighty-nine female athletes who played competitive basketball (n=40) or soccer (n=49) at the middle- or high-school level were analyzed with three-dimensional motion analysis during a drop vertical jump (DVJ), double- (SAG-DL) and single-leg forward jump (SAG-SL), and double- (FRONT-DL) and single-leg (FRONT-SL) lateral jump. Basketball players landed with less hip and/or knee excursion during all tasks (p<.05) except for the SAG-SL task, where basketball players landed with greater peak hip flexion angles (p=.04). The FRONT-SL task elicited the most distinct sport-specific differences, including decreased hip adduction (p<.001) angles, increased hip internal rotation (p=.003), and increased relative knee external rotation (p=.001) excursions in basketball players. Additionally, the FRONT-SL task elicited greater forces in knee abduction (p=.003) and lesser forces in hip adduction (p=.001) and knee external rotation (p<.001) in basketball players. Joint energetics were different during the FRONT-DL task, as basketball players exhibited less sagittal plane energy absorption at the hip (p<.001), and greater hip (p<.001) and knee (p=.001) joint stiffness. Sport-specific movement strategies were identified during all jump landing tasks, such that soccer players exhibited a more protective landing strategy than basketball players, justifying future efforts toward sport-specific ACL injury prevention programs.


#8 Somatotype And Body Composition In Young Soccer Players According To The Playing Position And Sport Success
Reference: J Strength Cond Res. 2017 Jul 17. doi: 10.1519/JSC.0000000000002125. [Epub ahead of print]
Authors: Cardenas-Fernandez V, Chinchilla-Minguet JL, Castillo-Rodriguez A
Summary: Soccer players undergo an evolution in their body composition throughout the growth and passage through the different base stages, that is, childhood, puberty and adolescence. The aim of this study was to analyze the morphology and body composition of U14, U16, and U19 soccer players, taking into account in addition, their sport success endorsed through the regularity participation and their relation with the different playing positions occupied during competition (goalkeeper, external defender, central defender, midfielder and forward/extreme). For that, a total of 174 male young soccer players were evaluated anthropometrically. Dominant somatotype of the players was, according to their playing position: meso-endomorphic in goalkeepers, central for external defenders, balanced ectomorph in central defenders, balanced mesomorph in the case of midfielders, and meso-ectomorph in forwards/extremes. Taking into account that sport performance is directly mediated by the body composition of athletes, the differences found suggest a marked specialization between the goalkeepers and forwards, establishing significant differences between them. Further studies would be needed to evaluate the influence of individual maturation development versus sports training on the conformation of a certain anthropometric profile of a soccer player and its relation with the different playing positions occupied on the pitch during the game.


#9 A Pilot Study of the Effect of Outsole Hardness on Lower Limb Kinematics and Kinetics during Soccer Related Movements
Reference: J Hum Kinet. 2017 Jun 22;57:17-27. doi: 10.1515/hukin-2017-0043. eCollection 2017 Jun.
Authors: Sun D, Mei Q, Baker JS, Jia X, Gu Y
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5504575/pdf/hukin-57-017.pdf
Summary: The purpose of this study was to investigate the effect of different outsole hardness of turf cleats shoes on the lower limb kinematics and kinetics of soccer players playing on artificial turf. The participants were required to complete tasks of straight running and 45° left sidestep cutting movements, respectively, at the speed of 4.5 ± 0.2 m/s on artificial turf. They were asked to randomly select turf cleats shoes with a soft outsole (SO), medium hardness outsole (MO) and hard outsole (HO). During the stance phase of straight running, peak pressure and force-time integral in medial forefoot (MFF) of players wearing cleats shoes with MO were significantly higher than those wearing cleats shoes with SO. During the stance phase of a 45° cutting maneuver, players wearing cleats shoes with SO showed significantly higher peak knee flexion and abduction angles than the HO group. Players wearing cleats shoes with SO also showed higher ankle dorsiflexion and inversion angles compared with those wearing cleats shoes with HO. The vertical average loading rate (VALR) as well as peak pressure and force-time integral in the heel (H) and lateral forefoot (LFF) regions of players wearing cleats shoes with HO were significantly higher than those wearing shoes with SO. On the contrary, peak pressure and force-time integral of players wearing shoes with SO were significantly higher than those wearing shoes with HO in MFF. A higher vertical loading rate and plantar pressure of some areas may increase the potential risk of metatarsal stress fractures and plantar fasciitis. Therefore, this finding about turf cleats shoes could give some theoretic support for the design of turf cleats shoes and material optimization in the future.


#10 Cardiopulmonary Performance During Maximal Exercise in Soccer Players with Alterations in Renal Function
Reference: J Hum Kinet. 2017 Jun 22;57:107-115. doi: 10.1515/hukin-2017-0052. eCollection 2017 Jun.
Summary: Morales AP, Sampaio-Jorge F, da Cruz Rangel LF, de Souza Menezes J, Leite TC, Ribeiro BG
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5504583/pdf/hukin-57-107.pdf
Summary: The aim of this study was to evaluate the curves of cardiorespiratory variables during cardiopulmonary exercise testing (CPET) in soccer players who had acute alterations in the glomerular filtration rate (GFR) after performing the pre-season training protocol. Sixteen male professional soccer players (25 ± 3 years; 179 ± 2 cm; and 77 ± 6 kg) were evaluated for oxygen uptake (VO2), heart rate (HR) and pulse relative oxygen (relative O2 Pulse) curves with intervals corresponding to 10% of the total duration of CPET. Athletes were grouped according to the GFR and classified as decreased GFR (dGFR; n = 8) and normal GFR (nGFR; n = 8). Athletes from the dGFR group exhibited lower VO2 values (p < 0.05) when 90% (dGFR 49.8 ± 4.0 vs. nGFR 54.4 ± 6.1 ml·kg-1·min-1) and 100% (dGFR 52.6 ± 4.1 vs. nGFR 57.4 ± 5.9 ml·kg-1·min-1) of the test was complete; HR high values (p < 0.05) when 90% (dGFR 183.7 ± 5.1 vs. nGFR 176.6 ± 4.8 bpm-1) and 100% (dGFR 188.1 ± 5.0 vs. nGFR 180.8 ± 4.8 bpm-1) of the test was complete; and lower relative O2 Pulse values (p < 0.05) when 70% (dGFR 25.6 ± 8.4 vs. nGFR 27.9 ± 9.7 ml·beat-1·kg-1), 80% (dGFR 26.6 ± 8.8 vs. nGFR 29.1 ± 10.0 ml·beat-1·kg-1), 90% (dGFR 27.1 ± 9.0 vs. nGFR 30.8 ± 10.6 ml·beat-1·kg-1) and 100% (dGFR 28 ± 9.2 vs. nGFR 31.8 ± 10.9 ml·beat-1·kg-1) of the test was complete. A correlation was found (r = -0.66, R2 = 0.44, p = 0.00) between lower VO2 peak and elevated levels of urinary protein excretion. In conclusion, soccer players with reduced kidney function after performing the pre-season training protocol also presented alterations in cardiopulmonary variables. We suggest that monitoring of renal function may be used to identify less conditioned soccer players.

Sat

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Jul

2017

Latest research in football - week 29 - 2017

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Field location and player roles as constraints on emergent 1-vs-1 interpersonal patterns of play in football
Reference: Hum Mov Sci. 2017 Jul 5;54:347-353. doi: 10.1016/j.humov.2017.06.008. [Epub ahead of print]
Authors: Laakso T, Travassos B, Liukkonen J, Davids K
Summary: This study examined effects of player roles on interpersonal patterns of coordination that sustain decision-making in 1-vs-1 sub-phases of football in different field locations near the goal (left-, middle- and right zone). Participants were fifteen U-16yrs players from a local competitive amateur team. To measure interpersonal patterns of coordination in the 1-vs-1 dyads we recorded: (i) the relative distance value between each attacker and defender to the centre of the goal, and (ii), the relative angle between the centre of the goal, each defender and attacker. Results revealed how variations in field locations near the goal (left-, middle- and right-zones) constrained the relative distance and relative angle values that emerged between them and the goal. It reveals that relative position of the goal is a key informational variable that sustained participants' behaviours for dribbling and shooting. Higher values of relative distance and angle were observed in the middle zone, compared to other zones. Players' roles also constitute a constraint on the interpersonal coordination for dribbling and shooting. Additionally, it seems that players' foot preference constrains the dynamics of interpersonal patterns of coordination between participants, especially in left and right zones. The findings suggest that to increase participants' opportunities for action, coaches should account with field positions, players' roles and preference foot.


#2 Influence of Cleats-Surface Interaction on the Performance and Risk of Injury in Soccer: A Systematic Review
Reference: Appl Bionics Biomech. 2017;2017:1305479. doi: 10.1155/2017/1305479. Epub 2017 Jun 8.
Authors: Silva DCF, Santos R, Vilas-Boas JP, Macedo R, Montes AM, Sousa ASP
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5480019/pdf/ABB2017-1305479.pdf
Summary: The purpose of the study was to review the influence of cleats-surface interaction on the performance and risk of injury in soccer athletes. Full experimental and original papers, written in English that studied the influence of soccer cleats on sports performance and injury risk in artificial or natural grass. Twenty-three articles were included in this review: nine related to performance and fourteen to injury risk. On artificial grass, the soft ground model on dry and wet conditions and the turf model in wet conditions are related to worse performance. Compared to rounded studs, bladed ones improve performance during changes of directions in both natural and synthetic grass. Cleat models presenting better traction on the stance leg improve ball velocity while those presenting a homogeneous pressure across the foot promote better kicking accuracy. Bladed studs can be considered less secure by increasing plantar pressure on lateral border. The turf model decrease peak plantar pressure compared to other studded models. The soft ground model provides lower performance especially on artificial grass, while the turf model provides a high protective effect in both fields.


#3 Deviating running kinematics and hamstring injury susceptibility in male soccer players: Cause or consequence?
Reference: Gait Posture. 2017 Jun 27;57:270-277. doi: 10.1016/j.gaitpost.2017.06.268. [Epub ahead of print]
Authors: Schuermans J, Van Tiggelen D, Palmans T, Danneels L, Witvrouw E
Summary: Although the vast majority of hamstring injuries in male soccer are sustained during high speed running, the association between sprinting kinematics and hamstring injury vulnerability has never been investigated prospectively in a cohort at risk. This study aimed to objectify the importance of lower limb and trunk kinematics during full sprint in hamstring injury susceptibility. At the end of the 2013 soccer season, three-dimensional kinematic data of the lower limb and trunk were collected during sprinting in a cohort consisting of 30 soccer players with a recent history of hamstring injury and 30 matched controls. Subsequently, a 1.5 season follow up was conducted for (re)injury registry. Ultimately, joint and segment motion patterns were submitted to retro- and prospective statistical curve analyses for injury risk prediction. Statistical analysis revealed that index injury occurrence was associated with higher levels of anterior pelvic tilting and thoracic side bending throughout the airborne (swing) phases of sprinting, whereas no kinematic differences during running were found when comparing players with a recent hamstring injury history with their matched controls. Deficient core stability, enabling excessive pelvis and trunk motion during swing, probably increases the primary injury risk. Although sprinting encompasses a relative risk of hamstring muscle failure in every athlete, running coordination demonstrated to be essential in hamstring injury prevention.


#4 Effects of lower-limb strength training on agility, repeated sprinting with changes of direction, leg peak power, and neuromuscular adaptations of soccer players
Reference: J Strength Cond Res. 2017 Jan 24. doi: 10.1519/JSC.0000000000001813. [Epub ahead of print]
Authors: Hammami M, Negra Y, Billaut F, Hermassi S, Shephard RJ, Chelly MS
Summary: We examined the effects on explosive muscular performance of incorporating 8 weeks strength training into the preparation of junior male soccer players, allocating subjects between an experimental group (E, n=19) and a matched control group (C, n=12). Controls maintained their regular training program, but the experimental group replaced a part of this schedule by strength training. Performance was assessed using running times (5m, 10m, 20m, 30 and 40m), a sprint test with 180° turns (S180°), a 9-3-6-3-9 m sprint with backward and forward running (SBF), a 4 x 5 m sprint test with turns, repeated shuttle sprinting, repeated changes of direction, squat (SJ) and counter-movement (CMJ) jumping, back half-squatting, and a force-velocity test. Electromyographic (EMG) activity of the vastus lateralis (VL), vastus medialis (VM) and rectus femoris (RF) muscles was recorded during jumping. Two-way ANOVA showed significant gains in E relative to C during the straight sprint (all distances). Scores of E increased substantially (p≤0.01) on S4 x 5 and SBF, and moderately on S180°. Leg peak power, SJ and CMJ were also enhanced, with significant increases in EMG activity. However, repeated-sprint parameters showed no significant changes. We conclude that biweekly strength training improves key components of performance in junior soccer players relative to standard in-season training.


#5 Physiological Characteristics of Projected Starters and Non-Starters in the Field Positions from a Division I Women's Soccer Team
Reference: Int J Exerc Sci. 2017 Jul 1;10(4):568-579. eCollection 2017.
Authors: Risso FG, Jalilvand F, Orjalo AJ, Moreno MR, Davis DL, Birmingham-Babauta SA, Stokes JJ, Stage AA, Liu TM, Giuliano DV, Lazar A, Lockie RG
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5466405/pdf/ijes-10-04-568.pdf
Summary: NCAA soccer features different substitution rules compared to FIFA-sanctioned matches, with a greater availability of players who can enter the game. This could influence the physiological characteristics of the field position starters (ST) and non-starters (NST) within a collegiate women's team, which has not been previously analyzed. Thus, 22 field players from the same Division I women's soccer squad completed: vertical and standing broad jumps; 30-meter (m) sprint (0-5, 0-10, 0-30 m intervals); pro-agility and 60-yard shuttle; and the Yo-Yo Intermittent Recovery Test Level 1. Players were defined into ST (n=10) and NST (n=12) by the coaching staff. A one-way ANOVA derived any significant (p≤0.05) between-group differences, and effect sizes were used for a magnitude-based inference analysis. Z-scores were also calculated to document worthwhile differences above or below the squad mean for the groups. The results showed no significant between-group differences for any of the performance tests. ST did have a worthwhile difference above the squad mean in the 0-10 and 0-30 m sprint intervals, while NST had a worthwhile difference below the squad mean in the 0-30 m interval. Physiological characteristics between ST and NST from the analyzed Division I squad were similar, although ST were generally faster. The similarities between ST and NST may be a function of the team's training, in that all players may complete the same workouts. Nonetheless, if all players exhibit similar physiological capacities, with appropriate substitutions by the coach a collegiate team should be able to maintain a high work-rate throughout a match.


#5 Epidemiologic comparisons of soccer-related injuries presenting to emergency departments and reported within high school and collegiate settings
Reference: Inj Epidemiol. 2017 Dec;4(1):19. doi: 10.1186/s40621-017-0116-9. Epub 2017 Jul 3.
Authors: Kerr ZY, Pierpoint LA, Currie DW, Wasserman EB, Comstock RD
Summary: Few studies compare sports injury patterns in different settings. This study described the epidemiology of soccer injuries presenting to emergency departments (EDs) and compared injuries presenting to EDs to injuries presenting to collegiate and high school athletic trainers (ATs). Soccer-related injuries (product code 1267) in the National Electronic Injury Surveillance System (NEISS) that were sustained by individuals at least two years of age in 2004-2013 were included. High School Reporting Information Online (HS RIO) data for high school soccer injuries during the 2005/06-2013/14 academic years were compared to NEISS data for those aged 14-17 years in 2005-2013. National Collegiate Athletic Association Injury Surveillance Program (NCAA-ISP) data for collegiate soccer injuries during the 2009/10-2013/14 academic years were compared to NEISS data for those aged 18-22 years in 2009-2013. All datasets included weights to calculate national estimates. Injury proportion ratios (IPRs) with 95% confidence intervals (CIs) compared nationally estimated injury distributions between the HS RIO/NCAA-ISP and NEISS data subsets. During the study period, 63,258 soccer-related injuries were captured by NEISS, which translates to an estimated 2,039,250 injuries seen at US EDs nationwide. Commonly injured body parts included the head/face (19.1%), ankle (17.6%), hand/wrist (15.3%), and knee (12.2%). Common diagnoses included sprains/strains (34.0%), fractures (22.2%), and contusions (17.7%). Compared to their respective age ranges in NEISS, sprains/strains comprised a larger proportion of injuries in HS RIO (48.3% vs. 33.7%; IPR = 1.38; 95% CI: 1.33, 1.42) and NCAA-ISP (51.3% vs. 37.0%; IPR = 1.39; 95% CI: 1.31, 1.46). In contrast, fractures comprised a smaller proportion of injuries in HS RIO than in NEISS (7.5% vs. 18.6%; IPR = 0.43; 95% CI: 0.39, 0.47) and NCAA-ISP (2.8% vs. 15.7%; IPR = 0.18; 95% CI: 0.14, 0.22). ATs more commonly reported injuries that are easily diagnosed and treated (e.g., sprains/strains); EDs more commonly reported injuries with longer recovery times and rehabilitation (e.g., fractures). Although ED surveillance data can identify the most severe sports-related injuries, high school and college sports surveillance may better describe the breadth of sports-related injuries. Our findings may provide further support for school-based sports medicine professionals, but further research is needed to comprehensively examine the potential economic and health-related benefits.


#6 Internal training load and its longitudinal relationship with seasonal player wellness in elite professional soccer
Reference: Physiol Behav. 2017 Jun 28;179:262-267. doi: 10.1016/j.physbeh.2017.06.021. [Epub ahead of print]
Authors: Clemente FM, Mendes B, Nikolaidis PT, Calvete F, Carriço S, Owen AL
Summary: Monitoring internal training load has been extensively used and described within team sport environments, however when compared to internal physiological measures such as heart rate (HR) and rating of perceived exertion (RPE), the literature is sparse. The primary aim of this investigation study was to assess differences of playing position on ITL, session-RPE and wellness across two different training microcycles (1 vs. 2 competitive games), in addition with examining the relationship between ITL and Hooper's Index across an entire season. Thirty-five professional soccer players from the Portuguese premier league participated in the study (25.7±5.0years; 182.3±6.4cm; 79.1±7.0kg). Analysis of variance revealed higher values of DOMS (Means(M): 3.33 vs. 3.10; p=0.001; effect Size (ES)=0.087), fatigue (M: 3.18 vs. 2.99; p=0.001; ES=0.060) and HI (M: 11.85 vs. 11.56; p=0.045; ES=0.034) in 2-game weeks compared with 1-game weeks. Correlation between ITL and HI levels found significant negative correlations between ITL and DOMS (ρ=-0.156), ITL and sleep (ρ=-0.109), ITL and fatigue (ρ=-0.225), ITL and stress (ρ=-0.188), and ITL and HI (ρ=-0.238) in 2-game weeks. Results from 1-game microcycle only highlighted negative correlations between ITL and stress (ρ=-0.080). It was concluded from the study that greater fatigue potential, muscle soreness, stress and ITL was significantly more apparent within a 2-game microcycle. As a result, care should be taken when planning the lead into and out of a 2-game fixture microcycle highlighting key specific recovery strategies to damped the increased stress effect. Additionally, the potential utilization of squad rotation strategies may be a positive approach with aim of managing the fatigue effect.


#7 Epidemiology of time loss groin injuries in a men's professional football league: a 2-year prospective study of 17 clubs and 606 players
Reference: Br J Sports Med. 2017 Jun 30. pii: bjsports-2016-097277. doi: 10.1136/bjsports-2016-097277. [Epub ahead of print]
Authors: Mosler AB, Weir A, Eirale C, Farooq A, Thorborg K, Whiteley RJ, Hӧlmich P, Crossley KM
Summary: Groin injury epidemiology has not previously been examined in an entire professional football league. We recorded and characterised time loss groin injuries sustained in the Qatar Stars League. Male players were observed prospectively from July 2013 to June 2015. Time loss injuries, individual training and match play exposure were recorded by club doctors using standardised surveillance methods. Groin injury incidence per 1000 playing hours was calculated, and descriptive statistics used to determine the prevalence and characteristics of groin injuries. The Doha agreement classification system was used to categorise all groin injuries. 606 footballers from 17 clubs were included, with 206/1145 (18%) time loss groin injuries sustained by 150 players, at an incidence of 1.0/1000 hours (95% CI 0.9 to 1.1). At a club level, 21% (IQR 10%-28%) of players experienced groin injuries each season and 6.6 (IQR 2.9-9.1) injuries were sustained per club per season. Of the 206 injuries, 16% were minimal (1-3 days), 25% mild (4-7 days), 41% moderate (8-28 days) and 18% severe (>28 days), with a median absence of 10 days/injury (IQR 5-22 days). The median days lost due to groin injury per club was 85 days per season (IQR 35-215 days). Adductor-related groin pain was the most common entity (68%) followed by iliopsoas (12%) and pubic-related (9%) groin pain. Groin pain caused time loss for one in five players each season. Adductor-related groin pain comprised 2/3 of all groin injuries. Improving treatment outcomes and preventing adductor-related groin pain has the potential to improve player availability in professional football.


American Football
#1 Association of Playing High School Football With Cognition and Mental Health Later in Life
Reference: JAMA Neurol. 2017 Jul 3. doi: 10.1001/jamaneurol.2017.1317. [Epub ahead of print]
Authors: Deshpande SK, Hasegawa RB, Rabinowitz AR, Whyte J, Roan CL, Tabatabaei A, Baiocchi M, Karlawish JH, Master CL, Small DS
Summary: American football is the largest participation sport in US high schools and is a leading cause of concussion among adolescents. Little is known about the long-term cognitive and mental health consequences of exposure to football-related head trauma at the high school level. The purpose was to estimate the association of playing high school football with cognitive impairment and depression at 65 years of age. A representative sample of male high school students who graduated from high school in Wisconsin in 1957 was studied. In this cohort study using data from the Wisconsin Longitudinal Study, football players were matched between March 1 and July 1, 2017, with controls along several baseline covariates such as adolescent IQ, family background, and educational level. For robustness, 3 versions of the control condition were considered: all controls, those who played a noncollision sport, and those who did not play any sport. A composite cognition measure of verbal fluency and memory and attention constructed from results of cognitive assessments administered at 65 years of age. A modified Center for Epidemiological Studies' Depression Scale score was used to measure depression. Secondary outcomes include results of individual cognitive tests, anger, anxiety, hostility, and heavy use of alcohol. Among the 3904 men (mean [SD] age, 64.4 [0.8] years at time of primary outcome measurement) in the study, after matching and model-based covariate adjustment, compared with each control condition, there was no statistically significant harmful association of playing football with a reduced composite cognition score (-0.04 reduction in cognition vs all controls; 97.5% CI, -0.14 to 0.05) or an increased modified Center for Epidemiological Studies' Depression Scale depression score (-1.75 reduction vs all controls; 97.5% CI, -3.24 to -0.26). After adjustment for multiple testing, playing football did not have a significant adverse association with any of the secondary outcomes, such as the likelihood of heavy alcohol use at 65 years of age (odds ratio, 0.68; 95% CI, 0.32-1.43). Cognitive and depression outcomes later in life were found to be similar for high school football players and their nonplaying counterparts from mid-1950s in Wisconsin. The risks of playing football today might be different than in the 1950s, but for current athletes, this study provides information on the risk of playing sports today that have a similar risk of head trauma as high school football played in the 1950s.

 


#2 Return to Sport and Performance After Anterior Cruciate Ligament Reconstruction in National Football League Linemen
Reference: Orthop J Sports Med. 2017 Jun 20;5(6):2325967117711681. doi: 10.1177/2325967117711681. eCollection 2017 Jun.
Authors: Cinque ME, Hannon CP, Bohl DD, Erickson BJ, Verma NN, Cole BJ, Bach BR Jr
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5480637/pdf/10.1177_2325967117711681.pdf
Summary: Tears of the anterior cruciate ligament (ACL) are common in the National Football League (NFL). The impact of these injuries on the careers of NFL linemen is unknown. The purpose was to define the percentage of NFL linemen who return to sport (RTS) after ACL reconstruction, the mean time to RTS, and the impact on performance compared with matched controls. Data on NFL offensive and defensive linemen who sustained an ACL tear and underwent ACL reconstruction between 1980 and 2015 were analyzed. Players were identified through NFL team websites, publicly available injury reports, player profiles, and press releases. Demographics and mean in-game performance data preinjury and post-ACL reconstruction were recorded. A player was deemed to have returned to sport if he played in at least 1 NFL game after his ACL reconstruction. A healthy control group was selected to compare in-game performance data and was matched with the study group on several parameters. Overall, 73 NFL linemen met the inclusion criteria; 47 (64.3%) returned to play after ACL reconstruction (62.5% of offensive linemen, 65.9% of defensive linemen). All offensive linemen successfully returned to play the season after injury. No difference existed in number of seasons, total number of games played, mean number of games played, or mean number of games started per season when offensive linemen who RTS after ACL reconstruction were compared with matched controls (all P > .05). Among defensive linemen who RTS, most returned the season after injury (88.9%). There was no difference between defensive linemen who RTS after ACL reconstruction and matched controls in any performance metrics as an average over the remainder of their career (all P > .05). However, NFL defensive linemen who tore their ACL played fewer total seasons than matched controls (P = .020). Overall, 64.3% of NFL offensive and defensive linemen who undergo ACL reconstruction returned to play. Linemen who RTS do so at a high level, with no difference in in-game performance or career duration when compared with matched controls.


Australian Football
#1 Return to Play and Player Performance After Anterior Cruciate Ligament Injury in Elite Australian Rules Football Players
Reference: Orthop J Sports Med. 2017 Jun 21;5(6):2325967117711885. doi: 10.1177/2325967117711885. eCollection 2017 Jun.
Authors: Liptak MG, Angel KR
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5482352/pdf/10.1177_2325967117711885.pdf
Summary: Australian Rules football is a highly aerobic and anaerobic game that at times requires players to perform cutting or pivoting maneuvers, potentially exposing them to anterior cruciate ligament (ACL) injury. At present, there are limited data available addressing the impact of ACL injury on return to play and preinjury form after ACL reconstruction. The purpose was to determine the prevalence of ACL injury and the incidence of further ACL injury, and to consider player return to play and return to preinjury form after ACL reconstruction. It was hypothesized that elite-level Australian Football League (AFL) players do not return to preinjury form until, at minimum, 2 years after returning to play. A retrospective analysis was undertaken on a cohort of elite AFL players who injured their ACL between 1990 and 2000. Return to play after ACL reconstruction was determined by the mean number of ball disposals, or release of the ball by the hand or foot, at 1, 2, and 3 years after return to play and compared with preinjury form. Associations between player and injury characteristics, method of reconstruction, and outcomes (return to play, preinjury form, and further ACL injury) were examined. During the included seasons, a total of 2723 AFL players were listed. Of these, 131 (4.8%) sustained an ACL injury, with 115 players eligible for inclusion. Of 115 players, 26% did not return to elite competition, while 28% of those who did return experienced further ACL injury. The adjusted mean number of disposals (± standard error of the mean) was significantly lower at 1 year (12.21 ± 0.63; P = .003), 2 years (12.09 ± 0.65; P = .008), and 3 years (11.78 ± 0.77; P = .01) after return to play compared with preinjury (14.23 ± 0.67). On average, players did not return to preinjury form by 3 years (P < .01). Players aged 30 years or older were less likely to return to play compared with younger players (P = .0002), moderate-weight players were more likely to return to play compared with lighter-weight players (P = .007), and there were significantly increased odds of not returning to play if the dominant side was injured (odds ratio, 0.10; 95% CI, 0.03-0.34; P = .0002). On average, AFL players do not return to their preinjury form after ACL injury and reconstruction, a common injury in this sporting population. This along with the high occurrence of reinjury highlights the career-threatening nature of ACL injury for elite AFL players.

Sat

22

Jul

2017

Latest research in football - week 28 - 2017

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Prone Hip Extension Muscle Recruitment is Associated with Hamstring Injury Risk in Amateur Soccer
Reference: Int J Sports Med. 2017 Jul 13. doi: 10.1055/s-0043-103016. [Epub ahead of print]
Authors: Schuermans J, Van Tiggelen D, Witvrouw E
Summary: 'Core stability' is considered essential in rehabilitation and prevention. Particularly with respect to hamstring injury prevention, assessment and training of lumbo-pelvic control is thought to be key. However, supporting scientific evidence is lacking. To explore the importance of proximal neuromuscular function with regard to hamstring injury susceptibility, this study investigated the association between the Prone Hip Extension (PHE) muscle activation pattern and hamstring injury incidence in amateur soccer players. 60 healthy male soccer players underwent a comprehensive clinical examination, comprising a range of motion assessments and the investigation of the posterior chain muscle activation pattern during PHE. Subsequently, hamstring injury incidence was recorded prospectively throughout a 1.5-season monitoring period. Players who were injured presented a PHE activation pattern that differed significantly from those who did not. Contrary to the controls, hamstring activity onset was significantly delayed (p=0.018), resulting in a shifted activation sequence. Players were 8 times more likely to get injured if the hamstring muscles were activated after the lumbar erector spinae instead of vice versa (p=0.009). Assessment of muscle recruitment during PHE demonstrated to be useful in injury prediction, suggesting that neuromuscular coordination in the posterior chain influences hamstring injury vulnerability.


#2 Effects of a Tapering Period on Physical Condition in Soccer Players
Reference: J Strength Cond Res. 2017 Jul 12. doi: 10.1519/JSC.0000000000002138. [Epub ahead of print]
Authors: Beltran-Valls MR, Camarero-Lopez G, Beltran-Garrido JV, Cecilia-Gallego P
Summary: The aim of this research was to analyze the effects of a two-week step tapering period on lower-limb muscle power, change of direction (COD) and acceleration capacities, and on the stress-recovery state in an amateur soccer team. Twenty-two male players were included in the study. Following a six-week progressive training, the sample was divided into: experimental group (n = 11), who did a two-week period of taper in which training volume was 50% reduced (intensity was kept high) and control group (n = 11), which kept on with the training. Muscle power (countermovement jump test), acceleration (10m sprint test), COD (Illinois test) and stress and recovery perceptions (RESTQ questionnaire) were evaluated before training, at the end of it (pre-tapering, PRE-TP) and after the tapering period (post-tapering, POST-TP). Following the taper, the experimental group in comparison to the control group showed significantly improved power (1029.71 ± 108.51 W/kg vs. 1084.21 ± 110.87 W/kg; p < 0.01), acceleration (1.72 ± 0.09 s vs. 1.67 ± 0.07 s; p < 0.05), and lower stress levels (1.9±0.5 vs. 1.6±0.5; p < 0.01) (PRE-TP vs. POST-TP, respectively). COD did not show significant changes. In conclusion, a two-week step tapering program was found to be an effective periodization strategy to increase muscle power and acceleration, and to reduce stress perception in soccer amateur players.


#3 Between-game variation of physical soccer performance measures in highly trained youth soccer players
Reference: J Strength Cond Res. 2017 Jul 12. doi: 10.1519/JSC.0000000000002132. [Epub ahead of print]
Authors: Doncaster G, Unnithan V
Summary: The purpose was to assess the between-game variation in measures of physical performance during 11 v 11 soccer match-play, over a short period of time, in highly trained youth soccer players. A single cohort observational study design was employed. Physical match performance data were collected from 17 male, highly trained youth soccer players (age: 13.3 ± 0.4 y) over three, 2 x 20min, 11 v 11 matches. Using 10 Hz GPS, the variables selected for analyses were total distance (TD), high-speed running (HSR), very high-speed running (VHSR), number of high-speed running efforts (HSReff) and number of very high-speed running efforts (VHSReff). Match data was also separated into cumulative 5 min epochs, to identify the peak 5 min epoch and the mean of the cumulative 5 min epochs for each match. Variability was quantified using the coefficient of variation (CV), Standard error of measurement (SEM) and intra-class correlation coefficient (ICC). Between- and within-player smallest worthwhile changes (SWC) were also calculated for each variable to aid in the interpretation of the data. Analysis of the variance between games reported a low CV for TD (3.8%) but larger CVs for HSR (33.3%), HSReff (35.4%) and VHSR and VHSReff (59.6 and 57.4 %, respectively). Analysis of 5 min epochs (peak and average) found an increase in the CVs beyond that of the values reported for the whole match. Between-player SWC in high intensity physical performance data ranged from 24.7 - 42.4 %, whereas within-player SWC ranged from 1.2 - 79.9%. The between-game variability of high and very high intensity activities in youth soccer players, across three soccer matches over a short period of time (2 weeks), is relatively 'large' and specific to the individual, thus highlighting the need for caution when interpreting physical performance data between games and players.


#4 Fatigue In U12 Soccer-7 Players During Repeated One-Day Tournament Games - A Pilot Study
Reference: J Strength Cond Res. 2017 Jul 12. doi: 10.1519/JSC.0000000000002141. [Epub ahead of print]
Authors: Sanchez-Sanchez J, Sanchez M, Hernandez D, Ramirez-Campillo R, Martinez C, Nakamura FY
Summary: The aim of this study was to describe and compare the distances and displacement speeds of U12 Soccer-7 athletes during four tournament Soccer-7 games (TG) played in less than 24-h (experimental condition) with those recorded during two league Soccer-7 games (LG) with 24-h of rest prior to the match (control condition). Ten participants (age = 10.3 ± 0.5 years) were recruited for the study. Main data analyzed during games included distance completed relative to match duration (Drel), maximal velocity and distance completed at different running speeds (including acceleration, deceleration, standing, walking, jogging, medium-intensity running, high-intensity running and sprinting). For data collection during games, athletes wore a GPS unit. Different (p<0.05) mean playing time was recorded during TG and LG (15.1 and 31.8 minutes/match, respectively). Drel during the four TG was maintained between 85.7 ± 8.5 m/min and 87.5 ± 8.5 m/min (P>0.05) and during the two LG between 84.2 ± 10.9 m/min and 87.5 ± 9.9 m/min (P>0.05). Moreover, similar Drel was recorded during TG and LG (86.8 m/min and 85.9 m/min, respectively). Compared to LG, during TG maximal velocity was lower (23.0 km/h and 21.3 km/h, respectively; P<0.05). In addition, compared to the last game of the tournament, in the preceding games the distance covered at low speeds (3.1-8.0 km/h) was lower (37.7% and 32.4%, respectively; P<0.05) and at high speeds (≥18.1 km/h) tend to be higher (2.5% and 3.3%, respectively). Therefore, compared with the control condition, accumulated Soccer-7 games with less than 24-h of inter-day rest negatively affects displacement speeds distribution (but not overall relative distances) in U12 Soccer-7 athletes. These results may help to better plan training and competition schedules to youth players.


#5 Effect of a professional soccer match in skin temperature of the lower limbs: a case study
Reference: J Exerc Rehabil. 2017 Jun 30;13(3):330-334. doi: 10.12965/jer.1734934.467. eCollection 2017 Jun.
Authors: de Andrade Fernandes A, Pimenta EM, Moreira DG, Sillero-Quintana M, Marins JCB, Morandi RF, Kanope T, Garcia ES
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5498090/pdf/jer-13-3-330.pdf
Summary: The purpose of this study is to analyze the relationship between lower limbs skin temperature (Tsk) recorded by infrared thermography and creatine kinase (CK) response following an official soccer game. A professional soccer player, from the first division Brazilian League, defender, 27 years and 183 cm of height was analyzed. Measures of Tsk with a thermal camera and blood CK concentrations were obtained 24 hr before (24H-PRE), 24 (24H-POST) and 48 hr (48H-POST) after an official match. The results showed that CK values were 193 U/L 24 hr before, rising to 1,083 U/L 24 hr after the game and 414 U/L 48 hr after the game. Anterior thigh Tsk was 31.5°C, 33.8°C, and 31.8°C in the moments 24H-PRE, 24H-POST, and 48H-POST, respectively. Similarly, anterior leg presented temperature of 31.2°C, 33.3°C, and 31.5°C at the same moments. Qualitative analysis of the thermograms showed that whole lower limbs are much warmer 24 hr after the match and certain areas as the right anterior thigh, the left anterior leg, both anterior ankles, and both posterior thighs have not fully recovered their initial Tsk 48 hr after the match. The results of this study indicate that participation in a professional soccer match can lead to significant increases in Tsk values measured by IRT 24 hr after the match. Considering this variable as an indicator of muscular damage, it could help in the process of training control, being part of an injury prevention program in professional soccer clubs.


#6 Quantifying changes in squat jump height across a season of men's collegiate soccer
Reference: J Strength Cond Res. 2017 Jul 8. doi: 10.1519/JSC.0000000000002118. [Epub ahead of print]
Authors: Sams ML, Sato K, DeWeese BH, Sayers AL, Stone MH
Summary: The purposes of this study were to examine the effectiveness of an athlete monitoring program in managing athlete neuromuscular fatigue across a men's collegiate soccer season as measured by changes in squat jump (SJ) height and to compare possible changes with session rating of perceived exertion (sRPE) training load (TL). Eighteen outfield Division I men's college soccer players performed SJ testing prior to each game of the fall season in addition to a baseline measurement at the start of pre-season. The athletes provided sRPE values after all training sessions, weight training, and games. Linear mixed modeling was used to compare changes in SJ height across the season with the baseline, and a correlation coefficient and single-lag cross-correlation coefficient were calculated between TL and changes in SJ height. No statistically significant decreases in SJ height occurred across the season, although a moderate practical decline occurred following the pre-season (-1.6 cm, ES = -0.70). The correlation between TL and changes in SJ height was statistically non-significant, while the cross-correlation was significant (r = 0.18, p = .48 and r = 0.55, p = 0.02, respectively). The athlete monitoring program was successful in managing the athletes' neuromuscular fatigue across the season as evidenced by the maintenance of SJ height and positive relationship between TL and changes in SJ height. Thus, SJ monitoring may serve as a useful fatigue monitoring tool for collegiate soccer athletes. Future study is needed relating changes in vertical jump performance to other markers of athlete preparedness and performance.


#7 Position specific acceleration and deceleration profiles in elite youth and senior soccer players
Reference: J Strength Cond Res. 2017 Apr 4. doi: 10.1519/JSC.0000000000001918. [Epub ahead of print]
Authors: Vigh-Larsen JF, Dalgas U, Andersen TB
Summary: The purpose of the study was to characterize and compare the position specific activity profiles of young and senior elite soccer players with special emphasis put on accelerations and decelerations. Eight professional senior matches were tracked using the ZXY tracking system and analyzed for number of accelerations and decelerations and running distances within different speed zones. Likewise, four U19- and five U17 matches were analyzed for comparison between youth and senior players. In senior players the total distance (TD) was 10776±107 m with 668±28 and 143±10 m being high-intensity running (HIR) and sprinting, respectively. Number of accelerations and decelerations were 81±2 and 84±3, with central defenders performing the lowest- and wide players the highest number. Declines were found between first and second halves for accelerations and decelerations (11±3 %), HIR (6±4 %) and TD (5±1 %), whereas sprinting distance did not differ. U19 players performed a higher number of accelerations, decelerations and TD compared to senior players. In conclusion, differences in number and distribution of accelerations and decelerations appeared between player positions, which is of importance when monitoring training and match loads and when prescribing specific training exercises. Further, youth players performed as much high-intensity activities as senior players indicating that this is not a discriminating physiological parameter between these players.


#8 Severe musculoskeletal time-loss injuries and symptoms of common mental disorders in professional soccer: a longitudinal analysis of 12-month follow-up data
Reference: Knee Surg Sports Traumatol Arthrosc. 2017 Jul 11. doi: 10.1007/s00167-017-4644-1. [Epub ahead of print]
Authors: Kiliç O, Aoki H, Goedhart E, Hagglund M, Kerkhoffs GMMJ, Kuijer PPFM, Walden M, Gouttebarge V
Summary: Psychological factors have shown to be predictors of injury in professional football. However, it seems that this is a two-way relationship, as severe musculoskeletal time-loss injuries have shown to be associated with the onset of symptoms of common mental disorders (CMD). There is no longitudinal study performed exploring this interaction between symptoms of CMD and injuries. The purpose of this study was to explore the interaction between severe musculoskeletal time-loss injuries and symptoms of CMD in professional football players over a 12-month period. Players were recruited by their national players' unions in five European countries. Symptoms of CMD included in the study were related to distress, anxiety/depression, sleep disturbance and adverse alcohol use. A total of 384 professional football players were enrolled in the study, of whom 262 (68%) completed the 12-month follow-up period. The mean age of the participants at baseline was 27 ± 5 years, and they had played professional football for 8 ± 5 years on average. Symptoms of CMD at baseline were not associated with the onset of severe musculoskeletal time-loss injuries during the follow-up period with relative risks (and 95% CI) ranging from 0.6 (0.3-1.0) to 1.0 (0.5-2.2). In contrast, severe musculoskeletal time-loss injuries reported at baseline were associated with the onset of symptoms of CMD during the follow-up period with relative risks ranging from 1.8 (0.8-3.7) to 6.9 (4.0-11.9). No relationship was found between symptoms of CMD and the onset of severe musculoskeletal time-loss injuries. However, professional football players who suffered from severe musculoskeletal time-loss injuries are likely to develop subsequent symptoms of CMD. This study emphasizes the need for an interdisciplinary medical approach, which not only focuses on the physical but also on the mental health of professional football players. An early identification of players at risk of symptoms of CMD, such as those suffering from severe musculoskeletal injuries, creates the opportunity for an interdisciplinary clinical medical team to treat the players timely and adequately.


#9 Individual ball possession in soccer
Reference: PLoS One. 2017 Jul 10;12(7):e0179953. doi: 10.1371/journal.pone.0179953. eCollection 2017.
Authors: Link D, Hoernig M
Download link: http://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0179953&type=printable
Summary: This paper describes models for detecting individual and team ball possession in soccer based on position data. The types of ball possession are classified as Individual Ball Possession (IBC), Individual Ball Action (IBA), Individual Ball Control (IBC), Team Ball Possession (TBP), Team Ball Control (TBC) und Team Playmaking (TPM) according to different starting points and endpoints and the type of ball control involved. The machine learning approach used is able to determine how long the ball spends in the sphere of influence of a player based on the distance between the players and the ball together with their direction of motion, speed and the acceleration of the ball. The degree of ball control exhibited during this phase is classified based on the spatio-temporal configuration of the player controlling the ball, the ball itself and opposing players using a Bayesian network. The evaluation and application of this approach uses data from 60 matches in the German Bundesliga season of 2013/14, including 69,667 IBA intervals. The identification rate was F = .88 for IBA and F = .83 for IBP, and the classification rate for IBC was κ = .67. Match analysis showed the following mean values per match: TBP 56:04 ± 5:12 min, TPM 50:01 ± 7:05 min and TBC 17:49 ± 8:13 min. There were 836 ± 424 IBC intervals per match and their number was significantly reduced by -5.1% from the 1st to 2nd half. The analysis of ball possession at the player level indicates shortest accumulated IBC times for the central forwards (0:49 ± 0:43 min) and the longest for goalkeepers (1:38 ± 0:58 min), central defenders (1:38 ± 1:09 min) and central midfielders (1:27 ± 1:08 min). The results could improve performance analysis in soccer, help to detect match events automatically, and allow discernment of higher value tactical structures, which is based on individual ball possession.


#10 A shower before bedtime may improve the sleep onset latency of youth soccer players
Reference: Eur J Sport Sci. 2017 Jul 9:1-10. doi: 10.1080/17461391.2017.1346147. [Epub ahead of print]
Authors: Whitworth-Turner C, Di Michele R, Muir I, Gregson W, Drust B
Summary: During the competitive season, soccer players are likely exposed to numerous factors that may disrupt the process of sleep. The current investigation looked to evaluate a practical sleep hygiene strategy (10-min showering at ∼40°C before lights out), within a group of 11 youth soccer players in comparison to normal sleeping conditions (control). Each condition consisted of three days within a randomised crossover trial design. Sleep information was collected using a commercial wireless bedside sleep monitor. Measures of skin temperature were evaluated using iButton skin thermistors to establish both distal and proximal skin temperatures and distal to proximal gradient. The shower intervention elevated distal skin temperature by 1.1°C (95% CI: 0.1-2.1°C, p = .04) on average prior to lights out. The elevation in distal temperature was also present during the first 30-min following lights out (1.0°C, 95% CI: 0.4-1.6°C, p < .01). The distal to proximal gradient also showed a significant effect between the conditions within the first 30-min after lights out (0.7°C, 95% CI: 0.3-1.2°C, p < .01). On average the sleep latency of the youth soccer players was -7-min lower (95% CI: -13 to -2 min, p < .01) and sleep efficiency +2% higher (95% CI: 1-3%; p < .01) in the shower condition. These findings demonstrate that a warm shower performed before lights out may offer a practical strategy to promote thermoregulatory changes that may advance sleep onset latency and improve sleep efficiency in athletes.


#11 Dynamics of tactical behaviour in association football when manipulating players' space of interaction
Reference: PLoS One. 2017 Jul 14;12(7):e0180773. doi: 10.1371/journal.pone.0180773. eCollection 2017.
Authors: Ric A, Torrents C, Goncalves B, Torres-Ronda L, Sampaio J, Hristovski R
Download link: http://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0180773&type=printable
Summary: The analysis of positional data in association football allows the spatial distribution of players during matches to be described in order to improve the understanding of tactical-related constraints on the behavioural dynamics of players. The aim of this study was to identify how players' spatial restrictions affected the exploratory tactical behaviour and constrained the perceptual-motor workspace of players in possession of the ball, as well as inter-player passing interactions. Nineteen professional outfield male players were divided into two teams of 10 and 9 players, respectively. The game was played under three spatial constraints: a) players were not allowed to move out of their allocated zones, except for the player in possession of the ball; b) players were allowed to move to an adjacent zone, and; c) non-specific spatial constraints. Positional data was captured using a 5 Hz interpolated GPS tracking system and used to define the configuration states of players for each second in time. The configuration state comprised 37 categories derived from tactical actions, distance from the nearest opponent, distance from the target and movement speed. Notational analysis of players in possession of the ball allowed the mean time of ball possession and the probabilities of passing the ball between players to be calculated. The results revealed that the players' long-term exploratory behaviour decreased and their short-term exploration increased when restricting their space of interaction. Relaxing players' positional constraints seemed to increase the speed of ball flow dynamics. Allowing players to move to an adjacent sub-area increased the probabilities of interaction with the full-back during play build-up. The instability of the coordinative state defined by being free from opponents when players had the ball possession was an invariant feature under all three task constraints. By allowing players to move to adjacent sub-areas, the coordinative state became highly unstable when the distance from the target decreased. Ball location relative to the scoring zone and interpersonal distance constitute key environmental information that constrains the players' coordinative behaviour. Based on our results, dynamic overlap is presented as a good option to capture tactical performance. Moreover, the selected collective (i.e. relational) variables would allow coaches to identify the effects of training drills on teams and players' behaviour. More research is needed considering these type variables to understand how the manipulation of constraints induce a more stable or flexible dynamical structure of tactical behaviour.


American Football
#1 Alcohol and violence in 2017 National Football League Super Bowl commercials
Reference: Health Promot Perspect. 2017 Jun 14;7(3):163-167. doi: 10.15171/hpp.2017.29. eCollection 2017.
Authors: MacLean SA, Basch CH, Garcia P
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5497368/pdf/hpp-7-163.pdf
Summary: The National Football League (NFL) Super Bowl is a widely-viewed sports event and the commercials are especially popular among viewers. Previous research has demonstrated risky health behaviors in advertisements aired during sporting events. The purpose of this study was to analyze the content of the advertisements aired during the 2017 NFL Super Bowl. This cross-sectional study involved examining the content of all commercials, with an emphasis on health-compromising behaviors. The themes and highlights of the advertisements were analyzed based on whether there was a reference to alcohol or violence. A total of 103 unique commercials were analyzed. The most common themes were humor (n=43), happiness (n=25), innovation (n=25), and enjoyment or relaxation (n=25).Alcohol was referenced in 13 (12.6%, 95% CI 7.5%, 20.4%) of the commercials. Advertisements with alcohol references were more likely to contain the themes of partying (odds ratio [OR]:16.2, 95% CI 1.4-193.4, P=0.041) and enjoyment or relaxation (OR: 4.7, 95% CI 1.4-15.6,P=0.014). There were 24 commercials with references to violence and these were more likely tobe promoting a movie (OR: 5.4, 95% CI 3.5-8.2, P<0.001) or television program (OR: 8.9,95% CI 2.6-30.26, P<0.001). Parents should consider whether it is appropriate for their children to watch a concentrated number of intense images containing references to alcohol and violence during this popular sporting event.


Australian Football
#1 The influence of contextual factors on running performance in female Australian Football match-play
Reference: J Strength Cond Res. 2017 Jul 12. doi: 10.1519/JSC.0000000000002142. [Epub ahead of print]
Authors: Black GM, Gabbett TJ Naughton G, Cole MH, Johnston RD, Dawson B
Summary: Given the recent growth of the professional status among multiple female football codes, the aim of this study is to investigate the effects of contextual factors on activity profiles and pacing strategies in female Australian football players. Thirty-five female Australian football players participated in this study. Global positioning system analysis was completed over one competitive season. Matches were separated into eight 10-minute periods. Greater distances were covered during the first half irrespective of playing position (ES = 0.39-0.50, Likelihood ≥90%). Throughout a number of periods half-backs (defensive players) covered greater distances during losses (ES ≥0.74, Likelihood ≥92%) and against Top 3 opponents (ES ≥1.0, Likelihood ≥ 97%). Midfielders and half-backs covered greater distances (ES ≥ 0.49, Likelihood ≥89%) in the final match period in winning compared with losing matches. A reduction in player work-rate is evident during the second half of matches. The influence of contextual factors varied across positional groups. However, it is clear coaches could use player rotation both early in the match in an attempt to delay the effect of fatigue and more frequently during the second half to increase running intensity.


#2 Radio Gaga? Intra-team communication of Australian Rules Football Umpires - Effect of radio communication on content, structure and frequency
Reference: Ergonomics. 2017 Jul 12:1-43. doi: 10.1080/00140139.2017.1353140. [Epub ahead of print]
Authors: Neville TJ, Salmon PM, Read GJM
Summary: Intra-team communication plays an important role in team effectiveness in various domains including sport. As such, it is a key consideration when introducing new tools within systems that utilise teams. The difference in intra-team communication of Australian Rules Football (AFL) umpiring teams was studied when umpiring with or without radio communications technology. A cross-sectional observational study was conducted to analyse the verbal communication of seven umpiring teams (20 participants) grouped according to their experience with radio communication. The results identified that radio communication technology increased the frequency and altered the structure of intra-team communication. Examination of the content of the intra-team communication identified impacts on the 'Big Five' teamwork behaviours and associated coordinating mechanisms. Analysis revealed that the communications utilised did not align with the closed-loop form of communication described in the Big Five model. Implications for teamwork models, coaching and training of AFL umpires are discussed.  Practitioner statement Assessing the impact of technology on performance is of interest to ergonomics practitioners. The impact of radio communications on teamwork is explored in the highly dynamic domain of AFL umpiring. When given radio technology, intra-team communication increased which supported teamwork behaviours such as backup behaviour and mutual performance monitoring.

Tue

18

Jul

2017

Latest research in football - week 27 - 2017

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Laboratory and Match Physiological Data from an Elite Male Collegiate Soccer Athlete
Reference: J Strength Cond Res. 2017 Jun 22. doi: 10.1519/JSC.0000000000002063. [Epub ahead of print]
Authors: Sapp RM, Aronhalt L, Landers-Ramos RQ, Spangenburg EE, Wang MQ, Hagberg JM
Summary: This study compared physiological data from an elite collegiate soccer player to that of his teammates over two seasons. The player of special interest (Player A) was the winner of the MAC Hermann trophy and was therefore considered the top player in NCAA division I soccer for each of the two seasons in which data was collected. Maximal oxygen consumption (VO2max) was measured during preseasons and heart rate was recorded during competitive matches. Polar training loads (PTL) were calculated by the Polar Team2 Pro (Polar USA) system based on time spent in HR zones. Player A had a lower VO2max than the team average in 2012 (56 vs. 61.5 ± 4.3 ml/kg/min) and a similar value in 2013 (54 vs. 56.9 ± 5.1 ml/kg/min). During matches, Player A showed consistent significant differences from the team in percentage of time spent at 70-79% HRmax (12.8 ± 5.5% vs. 10.1 ± 4.0%), 80-89% HRmax (54.3 ± 11.5% vs. 29.3 ± 6.8%), and 90-100% HRmax (23.1 ± 10.6% vs. 45.4 ± 8.5%). This led to a consistently lower PTL/min accumulated by Player A compared to his teammates (3.6 ± 0.4 vs. 4.4 ± 0.3), which may be beneficial over a season and may be related to his success. Thus, the ability to regulate moments of maximal exertion is useful in reducing training load and may be a characteristic of elite players, though whether our findings relate to differences in the playing style, position, or aerobic capacity of Player A, are unknown.

#2 Pitch size and Game Surface in Different Small-Sided Games. Global Indicators, Activity Profile and Acceleration of Female Soccer Players
Reference: J Strength Cond Res. 2017 Jun 22. doi: 10.1519/JSC.0000000000002090. [Epub ahead of print]
Authors: Lopez-Fernandez J, Gallardo L, Fernandez-Luna A, Villacanas V, Garcia-Unanue J, Sanchez-Sanchez J.
Summary: The aim of this research was to evaluate the influence of game surface and pitch size on the movement profile in female soccer players during Small-Sided-Games (SSGs) of 4 v 4. 16 women played three different 4-a-side (400 m, 600 m and 800 m) on three surfaces (ground [GR], artificial turf [AT] and natural grass [NG]). Time-motion variables were assessed through GPS devices (Spi Pro X, GPSports, Australia). GR had the worst outputs on most variables. NG achieved higher results than AT in terms of total distance [SSG 400 (+37.000 m; p=0.006); SSG 600 (+59.989 m; p<0.001); SSG 800 (+42.284 m; p=0.001)]. On the other hand, the smaller SSG (400) had the lowest values on most variables. However, while the middle SSG (600) presented higher output than the bigger one (800) for Body Load [NG (+7.745 a.u.; p<0.001); AT (+8.207 a.u.; p<0.001); GR (+5.879 a.u.; p<0.001)], it had lower results for High Intensity Distance [NG (-13.15 m; p=0.025); AT (-13.59 m; p=0.026)]. Despite women's performance being higher on AT than GR, the NG surface still showed the highest outcomes in the most intense SSG. Moreover, although the performance increase in bigger pitches, if the size is too large the outputs could be reduced.


#3 User Survey of 3 Ankle Braces in Soccer, Volleyball, and Running: Which Brace Fits Best?
Reference: J Athl Train. 2017 Jun 29. doi: 10.4085/1062-2050-52.4.06. [Epub ahead of print]
Authors: Janssen K, Van Den Berg A, Van Mechelen W, Verhagen E
Summary: Recurrence rates for ankle sprains are high. Therefore, preventive measures such as ankle bracing during sports are recommended. The study’s objective was to systematically evaluate the perceived ease of use, quality, comfort, stability, and hindrance of and the overall satisfaction with 3 contemporary brace types in 3 types of sports. Young adult recreational athletes (29 soccer players, 27 volleyball players, and 31 runners) participated in this study. Semirigid brace (SB), lace-up brace (LB), and compression brace (CB) were utilized Rating of perceived ease of use, quality, comfort, stability, and hindrance of and overall satisfaction with the brace types during sports on a 5-point Likert scale. The secondary outcome measure was participants' willingness to buy the tested brace. Overall, the 3 brace types received high mean scores for ease of use and quality. Soccer players preferred the CB over both alternatives, considering the higher scores for comfort (CB = 4.0, LB = 3.5, SB = 2.8), hindrance (CB = 3.7, LB = 2.9, SB = 2.8), overall satisfaction (CB = 3.6, LB = 3.0, SB = 2.5), and highest willingness to buy this brace. Volleyball players preferred the LB over both alternatives, considering the higher scores for stability (LB = 4.2, CB = 3.2, SB = 3.3), overall satisfaction (LB = 3.8, CB = 3.0, SB = 3.0), and greatest willingness to buy this brace. Runners preferred the CB over both alternatives considering the better score for hindrance (CB = 3.6, LB = 2.8, SB = 2.9) and greatest willingness to buy this brace. All 3 ankle brace types scored high on perceived ease of use and quality. Regarding the brace types, soccer players, volleyball players, and runners differed in their assessments of subjective evaluation of comfort, stability, hindrance, overall satisfaction, and willingness to buy the brace. Soccer players and runners preferred the CB, whereas volleyball players preferred the LB.


#4 Impact of a Soccer Game on Cardiac Biomarkers in Adolescent Players
Reference: Pediatr Exerc Sci. 2017 Jun 29:1-16. doi: 10.1123/pes.2017-0060. [Epub ahead of print]
Authors: Hosseini SM, Azizi M, Samadi A, Talebi N, Hannes G, Burtscher M
Summary: Biochemical markers such as cardiac troponin I (cTnI) and N-terminal pro B-type natriuretic peptide (NT-proBNP) have become indispensable tools for the diagnosis of myocardial injury, providing highly sensitive and specific information about cardiac cell damage and wall stress. The purpose of the present research was to examine the response of cardiac biomarkers to a soccer game in adolescent male soccer players. 22 trained adolescent male soccer players (14-16 years) were selected in a purposive manner. Blood samples were taken before, immediately after, and 2 and 24 hours after the game for the determination of cTnI and NT-proBNP. Serum concentration of cTnI and NT-proBNP were increased immediately and 2 hour after the soccer game (P<0.001). After 24 hours, the levels of cTnI had dropped but remained above baseline (p=0.002) whereas serum NT-proBNP levels had returned to baseline. At any time point, none of the values exceeded the upper reference value. This is the first study to investigate acute responses of cardiac biomarkers to a soccer game in adolescent male players. The post-game elevation of cardiac biomarkers and their rapid recovery are indicative of a physiological rather than a pathological response.


#5 Winners' Cup: a national football tournament brings together adolescent patients with cancer from all over Italy
Reference: Tumori. 2017 Jun 26:0. doi: 10.5301/tj.5000655. [Epub ahead of print]
Authors: Silva M, Chisari M, Signoroni S, Bassani A, Tagliabue L, Ricci A, Daversa M, Achini M, Spreafico F, Murelli M, Milano GM, Bisogno G, Coccoli L, Conte M, Garaventa A, Indolfi P, Perrotta S, Spinelli M, Mercolini F, Soloni P, Pierobon M, Di Cataldo A, Perillo T, Mascarin M, Coassin E, Veneroni L, Casanova M, Massimino M, Ferrari A
Summary: Società Scientifiche Italiane Insieme per gli Adolescenti con Malattie Onco-ematologiche (SIAMO) is an Italian nationwide scheme that focuses on adolescent patients with cancer. Some of its activities include promoting dedicated local projects at the various oncology centers all over the country and organizing events to improve awareness regarding cancer in adolescence. It is with these aims in mind that it organized the Winners' Cup, a football tournament between Italian adolescents who had (or had had) pediatric cancers. There were 144 young people 15 to 24 years old who arrived from 16 different treatment centers around the country to take part in the tournament and share their stories. Such an event had never been attempted before, in Italy at least. The Winners' Cup was a great success and an opportunity to focus attention on the particular clinical, psychological, and social needs of cancer patients in this age group.


#6 Online news media reporting of football-related fatalities in Australia: A matter of life and death
Reference: J Sci Med Sport. 2017 Jun 21. pii: S1440-2440(17)30479-6. doi: 10.1016/j.jsams.2017.06.015. [Epub ahead of print]
Authors: Fortington LV, Bekker S, Finch CF
Summary: While deaths in sports settings are rare, they do occur. To develop an understanding of the sports and people most at risk, and to identify opportunities for prevention, routine and systematic data detailing the occurrence of these fatalities is required. There is currently no routine reporting of data of this nature in Australia. As there is often strong community interest in these incidents, the media offers an opportunity for surveillance. However before this can occur, understanding of the terminology used by the media is required. The aim of this study was to identify the terminology most frequently used in online Australian news media coverage of football-related deaths. Three databases were searched for online news media reports of people who died while participating in football (all football codes) in Australia. A descriptive analysis of terminology was undertaken to identify the common language applied. Thirty-four football-related fatalities in Australia were identified between 2010-2016, via 149 separate articles. The most frequent terms identified in the media items were: Family; Club; Rugby; Football; Player; League; Died; Game; Death; Life; Loved; Hospital; Match; Young; Community; Playing; Friends; Sport; Heart; AFL [Australian Football League]. This study identified terminology used in reporting football-related fatalities in Australia, identifying common reference to terms relating to 'death' as metaphors and the frequent celebration of 'life.' The findings suggest that a reliance on researcher-generated terminology will be insufficient to reflect media discourse in prospective monitoring of sports deaths for surveillance.


#7 Effects of different re-warm up activities in football players' performance
Reference: PLoS One. 2017 Jun 29;12(6):e0180152. doi: 10.1371/journal.pone.0180152. eCollection 2017.
Authors: Abade E, Sampaio J, Goncalves B, Baptista J, Alves A, Viana J
Summary: Warm up routines are commonly used to optimize football performance and prevent injuries. Yet, official pre-match protocols may require players to passively rest for approximately 10 to 15 minutes between the warm up and the beginning of the match. Therefore, the aim of this study was to explore the effect of different re-warm up activities on the physical performance of football players. Twenty-Two Portuguese elite under-19 football players participated in the study conducted during the competitive season. Different re-warm up protocols were performed 6 minutes after the same standardized warm up in 4 consecutive days in a crossover controlled approach: without, eccentric, plyometric and repeated changes of direction. Vertical jump and Sprint performances were tested immediately after warm up and 12 minutes after warm up. Results showed that repeated changes of direction and plyometrics presented beneficial effects to jump and sprint. Different practical implications may be taken from the eccentric protocol since a vertical jump impairment was observed, suggesting a possibly harmful effect. The absence of re-warm up activities may be detrimental to players' physical performance. However, the inclusion of re-warm up prior to match is a complex issue, since the manipulation of volume, intensity and recovery may positively or negatively affect the subsequent performance. In fact, this exploratory study shows that eccentric exercise may be harmful for physical performance when performed prior a football match. However, plyometric and repeated changes of direction exercises seem to be simple, quick and efficient activities to attenuate losses in vertical jump and sprint capacity after warm up. Coaches should aim to develop individual optimal exercise modes in order to optimize physical performance after re warm activities.


#8 Alcohol Marketing during the UEFA EURO 2016 Football Tournament: A Frequency Analysis
Reference: Int J Environ Res Public Health. 2017 Jun 29;14(7). pii: E704. doi: 10.3390/ijerph14070704.
Authors: Purves RI, Critchlow N, Stead M, Adams J, Brown K
Summary: This study examined the frequency and nature of alcohol marketing references in broadcasts of the 2016 UEFA (Union of European Football Associations) European Championships football tournament in the United Kingdom (UK). Eighteen matches from across the tournament were recorded in full as broadcast in the UK, including all four matches featuring the English national team and all seven featuring the French national team. All visual and verbal references to alcohol marketing were recorded using a tool with high inter-rater reliability. A total of 2213 alcohol marketing references were recorded, an average of 122.94 per broadcast and 0.65 per broadcast minute (0.52 per minute in-play and 0.80 per minute out-of-play). Almost all references were visual (97.5%), with 77.9% occurring around the pitch border. Almost all (90.6%) were indirect references to alcohol brands (e.g., references to well-known slogans), compared to only 9.4% direct references to brands (e.g., brand names). The frequency of references to alcohol marketing was high. Although the overall proportion of direct brand references was low, the high proportion of indirect references demonstrates that alcohol producers were able to circumvent the French national law governing alcohol marketing (the Loi Évin) using indirect "alibi marketing". To ensure the spirit of the Loi Évin regulations are achieved, stricter enforcement may be required to limit exposure to alcohol marketing, particularly for young people.


#9 A systematic review of the technology-based assessment of visual perception and exploration behaviour in association football
Reference: J Sports Sci. 2017 Jun 26:1-20. doi: 10.1080/02640414.2017.1344780. [Epub ahead of print]
Authors: McGuckian TB, Cole MH, Pepping GJ
Summary: The purpose was to visually perceive opportunities for action, athletes rely on the movements of their eyes, head and body to explore their surrounding environment. To date, the specific types of technology and their efficacy for assessing the exploration behaviours of association footballers have not been systematically reviewed. This review aimed to synthesise the visual perception and exploration behaviours of footballers according to the task constraints, action requirements of the experimental task, and level of expertise of the athlete, in the context of the technology used to quantify the visual perception and exploration behaviours of footballers. A systematic search for papers that included keywords related to football, technology, and visual perception was conducted. All 38 included articles utilised eye-movement registration technology to quantify visual perception and exploration behaviour. The experimental domain appears to influence the visual perception behaviour of footballers, however no studies investigated exploration behaviours of footballers in open-play situations. Studies rarely utilised representative stimulus presentation or action requirements. To fully understand the visual perception requirements of athletes, it is recommended that future research seek to validate alternate technologies that are capable of investigating the eye, head and body movements associated with the exploration behaviours of footballers during representative open-play situations.


American Football
#1 Osteoarthritis Prevalence in Retired National Football League Players With a History of Concussion and Lower Extremity Injury
Reference: J Athl Train. 2017 Jun 2;52(6):518-525. doi: 10.4085/1062-6050-52.2.03.
Authors: Lynall RC, Pietrosimone B, Kerr ZY, Mauntel TC, Mihalik JP, Guskiewicz KM
Summary: Dynamic balance deficits have been described postconcussion, even after athletes return to play. Lower extremity (LE) musculoskeletal injury rates increase for up to 1 year after concussion, but the long-term musculoskeletal implications of concussion are unclear. The objective was to (1) examine the association of concussion and LE injury histories with osteoarthritis (OA) prevalence in retired National Football League players and (2) examine the association of concussion and LE injury histories with OA prevalence in those ≤55 years of age. We administered the Health Survey of Retired National Football League Players, which collects information about demographics, OA, LE injury, and concussion history. Twelve discrete categories were created based on concussion and LE injury history, ranging from 0 concussions and 0 LE injuries (referent group) to 3+ concussions and 2+ LE injuries. Binomial regression analysis modeled lifetime OA prevalence. Covariates were body mass index, age at the time of the survey, and total years playing professional football. Complete data were available for 2696 participants. Lifetime OA prevalence was smallest in the referent group (21.1%) and largest in the 3+ concussion and 2+ LE group (50.6%; 2.5 times the referent; 95% confidence interval [CI] = 2.1, 3.1). Participants in all concussion groups (1, 2, 3+) who reported a history of 0 LE injuries had a greater OA prevalence than the referent group. When participants were stratified by age, the ≤55 years of age, 3+ concussions, and 2+ LE injuries group prevalence ratio (3.6; 95% CI = 2.7, 5.2) was larger than that of the >55 years of age, 3+ concussions, and 2+ LE injuries group (1.8; 95% CI = 1.3, 2.4) compared with the respective referent groups. Concussion with or without a history of LE injury may be an important moderator of OA. Future researchers should seek to better understand the mechanisms that influence the association among concussion, LE injury, and OA.


Australian Football
#1 Subsequent Injuries Are More Common Than Injury Recurrences: An Analysis of 1 Season of Prospectively Collected Injuries in Professional Australian Football
Reference: Am J Sports Med. 2017 Jul;45(8):1921-1927. doi: 10.1177/0363546517691943. Epub 2017 Mar 9.
Authors: Finch CF, Cook J, Kunstler BE, Akram M, Orchard J
Summary: It is known that some people can, and do, sustain >1 injury over a playing season. However, there is currently little high-quality epidemiological evidence about the risk of, and relationships between, multiple and subsequent injuries. The purpose was to describe the subsequent injuries sustained by Australian Football League (AFL) players over 1 season, including their most common injury diagnoses. Within-player linked injury data on all date-ordered match-loss injuries sustained by AFL players during 1 full season were obtained. The total number of injuries per player was determined, and in those with >1 injury, the Subsequent Injury Classification (SIC) model was used to code all subsequent injuries based on their Orchard Sports Injury Classification System (OSICS) codes and the dates of injury. There were 860 newly recorded injuries in 543 players; 247 players (45.5%) sustained ≥1 subsequent injuries after an earlier injury, with 317 subsequent injuries (36.9% of all injuries) recorded overall. A subsequent injury generally occurred to a different body region and was therefore superficially unrelated to an index injury. However, 32.2% of all subsequent injuries were related to a previous injury in the same season. Hamstring injuries were the most common subsequent injury. The mean time between injuries decreased with an increasing number of subsequent injuries. When relationships between injuries are taken into account, there is a high level of subsequent (and multiple) injuries leading to missed games in an elite athlete group.


Gaelic Football
#1 The Positional Anthropometric and Performance Profile of Elite Gaelic Football Players
Reference: J Strength Cond Res. 2017 Jun 22. doi: 10.1519/JSC.0000000000002071. [Epub ahead of print]
Authors: Shovlin A, Roe M, Malone S, Collins K
Summary: The aim of the current investigation was to evaluate the variation in the anthropometric and performance characteristics of elite Gaelic football players with respect of position. One hundred and forty-eight elite Gaelic footballers underwent anthropometric (height, body mass, sum of seven skinfolds, % adipose tissue) and performance [counter movement jump height (CMJ), CMJ peak power, CMJ relative peak power, squat jump height (SJ), SJ peak power, SJ relative peak power, 5-, 10- and 20 m sprint times and Yo-Yo Intermittent Recovery Test Level 2 (Yo-YoIRT2)] during 'the early in-season' phase. Data were split into five positional groups (full-back, half-back, midfield, half-forward and full-forward). Higher %AT was observed in full forwards when compared to the half backs (p = 0.001), midfielders (p = 0.035) and half forwards (p = 0.021). Full forwards had significantly greater SJ (p = 0.036) and CMJ (p = 0.013) when compared to the midfielders with no other positional differences observed. No significant variation in sprint times was observed across positions. When Yo-YoIRT2 was considered, full forwards and full backs completed significantly lower distances compared to the middle three positional lines of, half backs, midfielders and half forwards (p = 0.00). The current study is the first to provide normative data for anthropometric and performance values of elite Gaelic football players which in turn can be utilised by coaches to generate appropriate training regimes to maximise position specific preparation for competitive match-play.

Mon

10

Jul

2017

Latest research in football - week 26 - 2017

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Computerized neuropsychological test performance of youth football players at different positions: A comparison of high and low contact players
Reference: Appl Neuropsychol Child. 2017 Feb 28:1-7. doi: 10.1080/21622965.2017.1290530. [Epub ahead of print]
Authors: Tsushima WT, Ahn HJ, Siu AM, Fukuyama T, Murata NM
Summary: The aim of this study was to examine the effects of head impact frequency on the neuropsychological test results of football players who participate in different positions on the team. Based on the biomechanical measures of head impact frequency reported in high school football, a High Contact group (n = 480) consisting of offensive and defensive linemen was compared with a Low Contact group (n = 640) comprised of receivers and defensive backs. The results revealed that the High Contact group obtained poorer performances on the Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT) on three Composite scores (Verbal Memory, Visual Motor Speed, Impulse Control) and the Total Symptom score compared to the Low Contact group. The present study is the first, to date, to report differences in the neuropsychological test performances of athletes who participate in high and low contact football positions. The findings raise tentative concerns that youth football players exposed to repetitive head trauma, including subconcussive impacts, may be at risk for lowered neuropsychological functioning and increased symptoms.


#2 Effects of inspiratory muscle training in professional women football players: a randomized sham-controlled trial
Reference: J Sports Sci. 2017 Jun 16:1-10. doi: 10.1080/02640414.2017.1340659. [Epub ahead of print]
Authors: Archiza B, Andaku DK, Caruso FCR, Bonjorno JC Jr, Oliveira CR, Ricci PA, Amaral ACD, Mattiello SM, Libardi CA, Phillips SA, Arena R, Borghi-Silva A
Summary: This study was conducted to determine the effects of inspiratory muscle training (IMT) on respiratory and peripheral muscles oxygenation during a maximal exercise tolerance test and on repeated-sprint ability (RSA) performance in professional women football players. Eighteen athletes were randomly assigned to one of the following groups: SHAM (n = 8) or IMT (n = 10). After a maximal incremental exercise test, all participants performed (on a different day) a time-to-exhaustion (Tlim) test. Peripheral and respiratory muscles oxygenation by near-infrared spectroscopy, breath-by-breath ventilatory and metabolic variables, and blood lactate concentration were measured. The RSA test was performed on a grass field. After a 6 week intervention, all athletes were reevaluated. Both groups showed increases in inspiratory muscles strength, exercise tolerance and RSA performance, however only the IMT group presented lower deoxyhemoglobin and total hemoglobin blood concentrations on intercostal muscles concomitantly to an increased oxyhemoglobin and total hemoglobin blood concentrations on vastus lateralis muscle during Tlim. In conclusion, these results may indicate the potential role of IMT to attenuate inspiratory muscles metaboreflex and consequently improve oxygen and blood supply to limb muscles during high-intensity exercise, with a potential impact on inspiratory muscle strength, exercise tolerance and sprints performance in professional women football players.


#3 Effects of oxygen therapy on wall-motion score index in patients with ST elevation myocardial infarction-the randomized SOCCER trial
Reference: Echocardiography. 2017 Jun 29. doi: 10.1111/echo.13599. [Epub ahead of print]
Authors: Khoshnood A, Akbarzadeh M, Roijer A, Meurling C, Carlsson M, Bhiladvala P, Hoglund P, Sparv D, Todorova L, Mokhtari A, Erlinge D, Ekelund U
Summary: Although oxygen (O2 ) is routinely used in patients with acute myocardial infarction (AMI), it may have negative effects. In this substudy of the SOCCER trial, we aimed to evaluate the effects of O2 -treatment on myocardial function in patients with ST elevation myocardial infarction (STEMI). Normoxic (≥94%) STEMI patients were randomized in the ambulance to either supplemental O2 or room air until the end of the percutaneous coronary intervention (PCI). The patients underwent echocardiography on day 2-3 after the PCI and once again after 6 months. The study endpoints were wall-motion score index (WMSI) and left ventricular ejection fraction (LVEF). Forty-six patients in the O2 group and 41 in the air group were included in the analysis. The index echocardiography showed no significant differences between the groups in WMSI (1.32±0.27 for O2 group vs 1.28±0.28 for air group) or LVEF (47.0±8.5% vs 49.2±8.1%). Nor were there differences at 6 months in WMSI (1.16±0.25 vs 1.14±0.24) or LVEF (53.5±5.8% vs 53.5±6.9%). The present findings indicate no harm or benefit of supplemental O2 on myocardial function in STEMI patients. Our results support that it is safe to withhold supplemental O2 in normoxic STEMI patients.


#4 Evidence of sub-optimal sleep in adolescent Middle Eastern academy soccer players which is exacerbated by sleep intermission proximal to dawn
Reference: Eur J Sport Sci. 2017 Jun 25:1-9. doi: 10.1080/17461391.2017.1341553. [Epub ahead of print]
Authors: Fowler PM, Paul DJ, Tomazoli G, Farooq A, Akenhead R, Taylor L
Summary: The purpose was to assess sleep patterns, quantity and quality in adolescent (16.2 ± 1.2 yr) Middle Eastern academy soccer players (n = 20) and the influence of an intermission upon these characteristics. On a 17-day training camp (located one time zone west of home) including three discrete matches, sleep was assessed pre- (PRE) and post-match (POST) via wrist actigraphy. Retrospective actigraphy analysis identified sleep characteristics, including if players experienced a sleep intermission (YES) or not (NO) proximal to dawn, and bedtime (hh:mm), get-up time (hh:mm), time in bed (h), sleep duration (h) and sleep efficiency (%). Within YES two bouts were identified (BOUT1 and BOUT2). No differences were seen between PRE and POST, nor between BOUT1 and BOUT2 (p > .05). Overall players did not meet National Sleep Foundation (NSF) guidelines (7:04 ± 1:16 h vs. recommended 8-10 h for 14-17 yr). Sleep duration was significantly reduced (∼ -13% or -1:06) in YES compared to NO (6:33 ± 1:05 vs. 7:29 ± 1:17, p < .01). Despite players in YES waking earlier due to an intermission, they did not compensate for this with a later wake time, rising significantly earlier compared to NO (09:40 ± 00:38 vs. 10:13 ± 00:40, p < .05). These players on average do not obtain sufficient sleep durations relative to NSF guidelines, with decrements increased by an intermission proximal to dawn. High inter- and intra-individual variance in the players sleep characteristics indicates the need for individualized sleep education strategies and interventions to promote appropriate sleep.


#5 Return to competition after an Achilles tendon rupture using both on and off the field load monitoring as guidance: A case report of a top-level soccer player
Reference: Phys Ther Sport. 2017 Apr 29. pii: S1466-853X(17)30187-6. doi: 10.1016/j.ptsp.2017.04.008. [Epub ahead of print]
Authors: Fanchini M, Impellizzeri FM, Silbernagel KG, Combi F, Benazzo F, Bizzini M
Summary: The purpose was to describe the Return to competition after Achilles Tendon rupture (ATR) in an elite soccer player. Return to sport (RTS) of a professional soccer player who suffered an ATR during a match. The RTS phase started 15 weeks after surgery and specific on-field activities were gradually introduced. Criteria used to monitor the transition through the different phases were strength and endurance of the calf muscle and ability to sustain specific on-field training loads (TL) monitored with Global Positioning System and heart-rate system. TLs were weekly compared to pre-injury values to evaluate recovery and to prescribe future sessions. A 39-year-old (height 178 cm, weight 75 kg) elite soccer defender player, playing in Italian Serie-A league. Days of absence were lower compared to a cohort presented in UEFA study (119 versus 161 ± 65 days, respectively). External-TL and Internal-TL were organized to gradually increase during RTS and resulted in higher values prior to return to competition compared to pre-injury values. Concentric plantar flexion peak torque increased till 9th months after surgery. Monitoring of the field activities allowed comparison with pre-injury values and provided a useful and functional criteria to pass return to team activity and competition.


#6 Head injuries in professional male football (soccer) over 13 years: 29% lower incidence rates after a rule change (red card)
Reference: Br J Sports Med. 2017 Jun 23. pii: bjsports-2016-097217. doi: 10.1136/bjsports-2016-097217. [Epub ahead of print]
Authors: Beaudouin F, Aus der Funten K, Troß T, Reinsberger C, Meyer T
Summary: Absolute numbers of head injuries in football (soccer) are considerable because of its high popularity and the large number of players. In 2006 a rule was changed to reduce head injuries. Players were given a red card (sent off) for intentional elbow-head contact. The purpse was to describe the head injury mechanism and examine the effect of the rule change. Based on continuously recorded data from the German football magazine "kicker", a database of all head injuries in the 1st German Male Bundesliga was generated comprising seasons 2000/01-2012/13. Injury mechanisms were analysed from video recordings. Injury incidence rates (IR) and 95% confidence intervals (95% CI) as well as incidence rate ratios (IRR) to assess differences before and after the rule change were calculated. 356 head injuries were recorded (IR 2.22, 95% CI 2.00 to 2.46 per 1000 match hours). Contact with another player caused most head injuries, more specifically because of head-head (34%) or elbow-head (17%) contacts. After the rule change, head injuries were reduced by 29% (IRR 0.71, 95% CI 0.57 to 0.86, p=0.002). Lacerations/abrasions declined by 42% (95% CI 0.39 to 0.85), concussions by 29% (95% CI 0.46 to 1.09), contusions by 18% (95% CI 0.43 to 1.55) and facial fractures by 16% (95% CI 0.55 to 1.28). This rule change appeared to reduce the risk of head injuries in men's professional football.


#7 Oxidative stress and antioxidant biomarker responses after a moderate-intensity soccer training session
Reference: Res Sports Med. 2017 Jun 28:1-11. doi: 10.1080/15438627.2017.1345738. [Epub ahead of print]
Authors: Mello R, Mello R, Gomes D, Paz GA, Nasser I, Miranda H, Salerno VP
Summary: The present study investigated the effects of a moderate-intensity soccer training session on the production of reactive oxygen species (ROS) and the antioxidant capacity in athletes along with the biomarkers creatine kinase and transaminases for lesions in muscle and liver cells. Twenty-two male soccer players participated in this study. Blood samples were collected 5 min before and after a moderate-intensity game simulation. The results showed a decrease in the concentration of reduced glutathione (GSH) from an elevation in the production of ROS that maintained the redox homeostasis. Although the session promoted an elevated energy demand, observed by an increase in lactate and glucose levels, damage to muscle and/or liver cells was only suggested by a significant elevation in the levels of alanine transaminase (ALT). Of the two biomarkers analysed, the results suggest that measurements of the ALT levels could be adopted as a method to monitor recovery in athletes.


#8 Daily Distribution of Macronutrient Intakes of Professional Soccer Players From the English Premier League
Reference: Int J Sport Nutr Exerc Metab. 2017 Jun 28:1-18. doi: 10.1123/ijsnem.2016-0265. [Epub ahead of print]
Authors: Anderson L, Naughton RJ, Close GL, Di Michele R, Morgans R, Drust B, Morton JP
Summary: The daily distribution of macronutrient intake can modulate aspects of training adaptations, performance and recovery. We therefore assessed the daily distribution of macronutrient intake (as assessed using food diaries supported by the remote food photographic method and 24 h recalls) of professional soccer players (n=6) of the English Premier League during a 7-day period consisting of two match days and five training days. On match days, average carbohydrate (CHO) content of the pre-match (<1.5 g.kg-1 body mass) and post-match (1 g.kg-1 body mass) meals (in recovery from an evening kick-off) were similar (P>0.05) though such intakes were lower than contemporary guidelines considered optimal for pre-match CHO intake and post-match recovery. On training days, we observed a skewed and hierarchical approach (P<0.05 for all comparisons) to protein feeding such that dinner (0.8 g.kg-1)>lunch (0.6 g.kg-1)>breakfast (0.3 g.kg-1)>evening snacks (0.1 g.kg-1). We conclude players may benefit from consuming greater amounts of CHO in both the pre-match and post-match meals so as to increase CHO availability and maximize rates of muscle glycogen re-synthesis, respectively. Furthermore, attention should also be given to ensuring even daily distribution of protein intake so as to potentially promote components of training adaptation.


#9 A Review Of Field-Based Assessments Of Neuromuscular Control And Their Utility In Male Youth Soccer Players
Reference: J Strength Cond Res. 2017 Jun 22. doi: 10.1519/JSC.0000000000002069. [Epub ahead of print]
Authors: Read PJ, Oliver JL, De Ste Croix MBA, Myer GD, Lloyd RS
Summary: Lower extremity injuries in male youth soccer are common and equate to a substantial time-loss from training and competitions during the course of a season. Extended periods of absence will impact player involvement in skill and physical development activities, as well as participation in competitive match play. Neuromuscular risk factors for lower extremity injury in male youth soccer players can be categorized into quadriceps dominance; leg dominance; ligament dominance; trunk dominance and reduced dynamic stability. Valid screening methods to identify risk factors that are practically viable are needed for youth athletes who may be at a greater risk of injury in soccer. While field-based tests of neuromuscular control provide a reliable option for the assessment of injury risk in adults and females, less data are available in male youth soccer players and further research is required to examine their ability to predict injury risk. This article provides a review of the current literature pertaining to field-based screening tests and critically appraises their suitability for use with male youth soccer players. Currently the only method that has been validated in male youth soccer players is the landing error scoring system. Asymmetrical anterior reach measured during the Y-Balance test may also be considered due to its strong predictive ability in male youth basketball players; however, further research is required to fully support its use with soccer players.


#10 Evaluation Of The Official Match External Load In Soccer Players With Cerebral Palsy
Reference: J Strength Cond Res. 2017 Jun 22. doi: 10.1519/JSC.0000000000002085. [Epub ahead of print]
Authors: Yanci J, Castillo D, Iturricastillo A, Reina R
Summary: The aims of this study were to analyze the official match external loads (i.e. total distance [TD], distance covered at different speeds, accelerations, decelerations, player load [PL], peak metabolic power [PMP] and changes of direction [CODs]) of football players with cerebral palsy (CP), and to determine the external loads according to playing time (i.e. < 20 min, 20-40 min and > 40 min). The external load of thirty-one international football players with CP (23.0 ± 6.6 years; 69.1 ± 9.0 kg; 174.8 ± 7.3 cm) was analyzed during a World Championship Qualification Tournament (n = 8 matches, 58 individual observations). Results showed that the football players with CP, covered less distance at high intensity running and sprinting, performing a smaller number of moderate and high intensity accelerations and decelerations, had a lower PL and made fewer CODs in official matches compared to conventional football players as reported in other studies. The number of minutes played by the players (i.e. < 20 min, 20-40 min and > 40 min) could significantly influence the players' match external load (ES = 0.3-5.5, small to extremely large). The impairments presented by football players with CP affect players' match external loads, especially in short-term high-intensity neuromuscular actions.

Fri

07

Jul

2017

Latest research in football - week 25 - 2017

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 The provision of medical care in English professional football: An update.
Reference: J Sci Med Sport. 2017 May 25. pii: S1440-2440(17)30430-9. doi: 10.1016/j.jsams.2017.05.004. [Epub ahead of print]
Authors: Malcolm D, Scott-Bell A, Waddington I
Summary: The purpose was to compare the current methods of appointment, qualifications and occupational experience of club doctors and physiotherapists in English professional football with (i) those outlined in a study published in 1999, and (ii) Football Association (FA) medical regulations. Postal questionnaire survey of (head) doctors and physiotherapists at each of the clubs in the English Premiership, Championship and Football Leagues 1 and 2. Response rates of 35.8% and 45.6% respectively were obtained. The majority of football club doctors are GPs who have sports medicine qualifications and relevant occupational experience. Time commitments vary from full time to a few hours per week. Most are appointed through personal contacts rather than job advertisements and/or interview. Almost all football clubs have a chartered physiotherapist, many of whom have a postgraduate qualification. They work full time and long hours. Most are appointed through personal contacts rather than job advertisements. They are frequently interviewed but not always by someone qualified to judge their professional expertise. Football club medical provision has become more extensive and increasingly professional over the last 10-20years, with better qualified, more career-oriented and more formally contracted staff. It is likely that clinical autonomy has subsequently increased. However recruitment procedures still need to be improved, especially in relation to advertising vacancies, interviewing candidates, and including medical personnel on interview panels. In two aspects clubs appear not to be compliant with current FA medical regulations.


#2 Pseudoaneurysm of the Anterior Tibial Artery following Ankle Arthroscopy in a Soccer Player
Reference: Case Rep Orthop. 2017;2017:2865971. doi: 10.1155/2017/2865971. Epub 2017 May 18.
Authors: Tonogai I, Matsuura T, Iwame T, Wada K, Takasago T, Goto T, Hamada D, Kawatani Y, Fujimoto E, Kitagawa T, Takao S, Iwamoto S, Yamanaka M, Harada M, Sairyo K
Summary: Ankle arthroscopy carries a lower risk of vascular complications when standard anterolateral and anteromedial portals are used. However, the thickness of the fat pad at the anterior ankle affords little protection for the thin-walled anterior tibial artery, rendering it susceptible to indirect damage during procedures performed on the anterior ankle joint. To our knowledge, only 11 cases of pseudoaneurysm involving the anterior tibial artery after ankle arthroscopy have been described in the literature. Here we reported a rare case of a 19-year-old soccer player who presented with pseudoaneurysm of the anterior tibial artery following ankle arthroscopy using an ankle distraction method and underwent anastomosis for the anterior tibial artery injury. Excessive distraction of the ankle puts the neurovascular structures at greater risk for iatrogenic injury of the anterior tibial artery during ankle arthroscopy. Surgeons should look carefully for postoperative ankle swelling and pain after ankle arthroscopy.


#3 The effect of air pollution on diurnal variation of performance in anaerobic tests, cardiovascular and hematological parameters, and blood gases on soccer players following the Yo-Yo Intermittent Recovery Test Level-1
Reference: Chronobiol Int. 2017 Jun 14:1-18. doi: 10.1080/07420528.2017.1325896. [Epub ahead of print]
Authors: Boussetta N, Abedelmalek S, Aloui K, Souissi N
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5451781/pdf/CRIOR2017-2865971.pdf
Summary: This study aimed to investigate the effect of air pollution on diurnal variation of performance in anaerobic tests, cardiovascular and hematological parameters, and blood gases on soccer players following the Yo-Yo Intermittent Recovery Test Level-1 (YYIRT1). In a randomized order, 11 healthy soccer players (mean age: 21.8 [range: 20-24] years; height: 178.00 [range: 1.64-1.83] cm; body mass index [BMI]: 23.57 [range: 20.45-28.03] kg.m-2) performed a YYIRT1 at two different times of day (TOD) (08:00 h and 18:00 h) in two areas (i.e. polluted (PA) and non-polluted (NPA)) with a recovery period of ≥ 72 h in between, to determine the maximal oxygen uptake (VO2max). In each test session: resting oral temperature is measured, anaerobic performances (pre- and post-YYIRT1) were performed, cardiovascular parameters and blood samples were collected at: rest, 3 min and 60 min after the YYIRT1, to assess blood gases and hematological parameters. Our results showed that, agility performance, VO2max, red blood cells (RBC), hemoglobin (Hb), pH, and bicarbonate levels (HCO3-) decrease significantly (p < 0.001) following the YYIRT1 in PA compared to NPA. Likewise, the heart rate (HR), systolic blood pressure (SBP), platelets (PLT), white blood cells (WBC), neutrophiles (NEUT), lymphocytes (LYM), and partial pressure of CO2 levels (PvCO2) were significantly higher (p < 0.001) in PA. This effect was slightly accentuated at 18:00 h for some parameters (i.e. Agility, HCO3-, HR, PvCO2, RBC, SBP). However, performances of sprint and Sargent jump test (SJT), oral temperature, rate of perceived exertion scales (RPE), partial pressure of O2 (PvO2), diastolic blood pressure (DBP), and monocytes (MON) were not affected by pollution (p > 0.05). In conclusion, pollution seems to be critical for health stability and performance in response to YYIRT1 especially in the evening and the winter season. Therefore, coaches and athletes should draw attention to the potential importance of land use planning in their training sessions and competitions in the morning in polluted area to minimize the risk of pollution exposure.


#4 The relationship between jumping performance, isokinetic strength and dynamic postural control in elite youth soccer players
Reference: J Sports Med Phys Fitness. 2017 Jun 21. doi: 10.23736/S0022-4707.17.07289-9. [Epub ahead of print]
Authors: Sliwowski R, Grygorowicz M, Wieczorek A, Jadczak L
Summary: The aim of this study was (i) to investigate the relationship between vertical jumping performance, isokinetic strength of knee extensors/flexors, and postural priority and (ii) an attempt to describe a multiple regression model that accounts for the effects of selected parameters of isokinetic strength and postural priority on vertical jumping performance. Thirty-one professional male soccer players, aged from 17 to 20 years, participated in this study (mean age: ± SD 18,6 ± 1.26 years; height: 1,78 ± 0,74 m and weight: 73,1 ± 6,77 kg). The correlations between isokinetic knee strength, jumping performance, and postural control were evaluated using the Pearson correlation coefficient. A linear regression model was used to evaluate the effect of hamstrings and quadriceps peak torque of both legs at 60o·s-1, total work of both legs at 240o·s-1, and postural priority on jumping performance. The peak torque of right leg knee flexor (quadriceps) muscles, evaluated at 60o·s-1 speed, showed correlations with counter movement jump, 30 second jumping and squat jump (p=0.005, p=0.003, and p=0.007, respectively). We also observed a strong relationship between counter movement jump and 30 second jumping and peak torque of left leg evaluated at the same speed of 60o·s-1 (p=0.26 and p=0.22, respectively). No significant correlations were found between any of the jumping tests and peak torque of knee extensors of both legs at 60o·s-1. For the 30 second jumping test, it appears that jumping endurance has a significant relationship with total work of knee flexors for right and left legs at 240o·s-1. The results of this study demonstrate practical implications for soccer performance, but further exploration is required.


#5 Comparison of knowledge, perception and attitudes of concussion in previously concussed versus non-concussed youth soccer players
Reference: Phys Sportsmed. 2017 Jun 21. doi: 10.1080/00913847.2017.1345569. [Epub ahead of print]
Authors: Myrdal CN, Huang S, Beach HN, Waterbrook AL
Summary: The purpose was to examine if history of concussion is correlated with a difference in knowledge, attitude, and perception of concussive injuries in youth soccer players. A convenience sample of youth soccer athletes aged 14 to 18 years completed a survey assessing prior history of concussive injury, knowledge of concussive injury, self-reporting attitudes, and perception of the injury. The survey consists of 16 knowledge questions (eleven on a scale of 1-2, and five on a scale of 1-4) and 12 attitude questions (seven on a scale of 1-4, and five on a scale of 1-5). The primary outcomes are the total scores calculated by summing the standardized raw scores for all knowledge questions and attitude questions, respectively. Linear regression was used to estimate the mean difference in the primary outcomes between previously concussed and non-concussed athletes (calculated as previously concussed - non-concussed). Surveys were obtained from 90 athletes, with 32 (36%) previously sustaining at least one concussion. Thirty-one out of these 32 concussions were diagnosed by a medical provider. On average, the mean total raw scores of all knowledge questions are 34.6 (82.2% of 42 possible points) and 33.7 (80.2% of 42 total points) for previously concussed and non-concussed athletes, respectively, and the mean total raw scores of all attitude questions are 38.7 (72.9% of 53 possible points) and 39.6 (74.7% of 53 possible points), respectively. Mean differences estimated from univariate linear regression in the standardized total scores of knowledge questions and attitude questions are 1.56(95% confidence interval: -1.52-4.65) and -1.23 (%95 confidence interval: -4.64-2.19), respectively. Adjusting for age and years of playing soccer gave similar results. Although we did not find significant differences between previously concussed and non-concussed athletes in either the knowledge or the attitude questions as measured by their total scores, this study showed a high level of awareness of concussion in youth soccer players, while still highlighting a need for education. Limited distinctions were made among subgroups of players, suggesting directions of future research in investigating the role that outside factors may have on knowledge and perception of concussion.


#6 Are Change of Direction Speed and Reactive Agility Useful for Determining the Optimal Field Position for Young Soccer Players?
Reference: J Sports Sci Med. 2017 Jun 1;16(2):247-253. eCollection 2017 Jun.
Authors: Fiorilli G, Iuliano E, Mitrotasios M, Pistone EM, Aquino G, Calcagno G, di Cagno A
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5465987/pdf/jssm-16-247.pdf
Summary: Change Of Direction Speed (CODS) and Reactive Agility (RA) are two determining factors in the ability of young soccer players. We aimed to verify if CODS and RA could be useful in order to establish the best young soccer player field position. Ninety-two elite soccer players (15.18 ± 1.21 years, weight 59.18 ± 9.93, height 1.72 ± 0.08, BMI 19.76 ± 2.22), belonging to two youth categories from the Italian First and Second Divisions, volunteered in this study. The participants included 32 defenders (15.06 ± 0.80 years), 37 midfielders (15.11 ± 0.84 years) and 23 forwards (15.48 ± 1.16 years), and they underwent two tests, each one performed in two different ways: the Y-Agility Test, carried out in a planned and reactive mode (Y-PLAN and Y-REAC), and the Illinois for Change of Direction Test (ICODT) performed with and without the ball. REAC-INDEX, which represents the index of reactivity, was calculated as Y-REAC minus Y-PLAN. The difference between the two scores of ICODT (ICODT with the ball minus ICODT without the ball) represents the TECHN-INDEX. Multivariate Analysis of Variances (MANOVA) was used to evaluate significant differences among all position groups, for all the test scores. MANOVA showed no significant differences in test scores or in TECHN-INDEX among the groups, except for the forwards, who were significantly more reactive than the defenders (p < 0.05). The strong and significant Pearson's Correlation between ICODT with and without the ball (p < 0.01) demonstrated that physical and technical preparations have the same relevance in all positions. No significant differences were found among players in different field positions for CODS and RA performances, both with and without the ball. This study does not recommend to use RA and CODS as indicators to assign the players roles in youth soccer.


#7 Premier League academy soccer players' experiences of competing in a tournament bio-banded for biological maturation
Reference: J Sports Sci. 2017 Jun 19:1-9. doi: 10.1080/02640414.2017.1340656. [Epub ahead of print]
Authors: Cumming SP, Brown DJ, Mitchell S, Bunce J, Hunt D, Hedges C, Crane G, Gross A, Scott S, Franklin E, Breakspear D, Dennison L, White P, Cain A, Eisenmann JC, Malina RM
Summary: Individual differences in the growth and maturation have been shown to impact player performance and development in youth soccer. This study investigated Premier League academy players' experiences of participating in a tournament bio-banded for biological maturation. Players (N = 66) from four professional soccer clubs aged 11 and 14 years and between 85-90% of adult stature participated in a tournament. Players competed in three 11 vs 11 games on a full size pitch with 25-min halves. Sixteen players participated in four 15-min focus groups and were asked to describe their experiences of participating in the bio-banded tournament in comparison to age group competition. All players described their experience as positive and recommended the Premier League integrate bio-banding into the existing games programme. In comparison to age-group competitions, early maturing players described the bio-banded games more physically challenging, and found that they had to adapt their style of play placing a greater emphasis on technique and tactics. Late maturing players considered the games to be less physically challenging, yet appreciated the having more opportunity to use, develop and demonstrate their technical, physical, and psychological competencies. Bio-banding strategies appear to contribute positively towards the holistic development of young soccer players.


#8 Acute Modification of Cardiac Autonomic Function of High-Intensity Interval Training in Collegiate Male Soccer Players with Different Chronotype: A Cross-Over Study
Reference: J Sports Sci Med. 2017 Jun 1;16(2):286-294. eCollection 2017 Jun.
Authors: Bonato M, Agnello L, Galasso L, Montaruli A, Roveda E, Merati G, La Torre A, Vitale JA
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5465992/pdf/jssm-16-286.pdf
Summary: The purpose of this study was to evaluate if the time of the day (8.00 a.m. vs 8.00 p.m.) and chronotype could influence autonomic cardiac control in soccer players in relation to an acute session of high-intensity interval training. The morningness-eveningness questionnaire was administered to recruit Morning-type and Evening-type collegiate male soccer players. Therefore, 24 players (12 Morning-types and 12 Evening-types) were randomly assigned, to either morning (n = 12; age 23 ± 3 years; height 1.75 ± 0.07 m; body mass 73 ± 10 kg; weekly training volume 8 2 hours), or evening (n = 12; age 21 ± 3 years; height 1.76 ± 0.05 m; body mass 75 ± 11 kg; weekly training volume 8 ± 3 hours) training. Heart Rate Variability vagal and sympatho/vagal indices were calculated in time, frequency and complexity domains at rest, before, after 12 and 24 hours of high-intensity interval training. Before evening training session, a higher resting heart rate was observed which was determined by a marked parasympathetic withdrawal with a sympathetic predominance. Moreover, Evening-type subjects during morning training session, present a significant higher heart rate that corresponded to significant higher vagal indices with a significant lower parasympathetic tone that returned to the rest values after 24 hours of the cessation of high-intensity interval training exercise. On the contrary, Morning-type subjects did not reveal any significant differences with Evening-Type subjects during evening high-intensity interval training session. Stress response of high-intensity interval training is influenced by both the time of the day and by the chronotype. Understanding the Heart Rate Variability response to high-intensity interval training can be an additional important procedure for evaluating of cardiovascular recovery in soccer players. Moreover, these results suggest that an athlete's chronotype should be taken into account when scheduling a high-intensity interval training exercise.


#9 Clinical benefit of the FIFA 11 programme for the prevention of hamstring and lateral ankle ligament injuries among amateur soccer players
Reference: Inj Prev. 2017 Jun 22. pii: injuryprev-2016-042267. doi: 10.1136/injuryprev-2016-042267. [Epub ahead of print]
Authors: Nouni-Garcia R, Carratala-Munuera C, Orozco-Beltran D, Lopez-Pineda A, Asensio-Garcia MR, Gil-Guillen VF
Summary: The purpose was to analyse the relationship between the implementation of 'the 11' protocol during the regular season in a men's amateur soccer team and the rate of hamstring and lateral ankle ligament (LAL) injuries, and to estimate the clinical benefit of the programme according to the type of injury and the position field. This cohort study was conducted in two different men's amateur soccer teams. During two seasons, the exposed group (43 players) performed 'the 11' protocol twice a week, and the unexposed group (43 players) performed the regular training programme. All players trained three times per week for 1.5 hours per day. Data collection was performed for every 1000 hours of play. 18 hamstring injuries (injury rate (IR) of 2.26 injuries/1000 training+competition hours) and 15 LAL injuries (IR of 1.88 injuries/1000) were registered in the exposed group. In the unexposed group, there were 25 LAL injuries (IR of 3.14 injuries/1000) and 35 hamstring injuries (IR of 4.39 injuries/1000). The number needed to treat to prevent one new case was 3.9 in LAL injuries, 3.31 in biceps femoris injuries and 10.7 in recurrent hamstring injuries. 'The 11' programme reduced the incidence of hamstring and LAL injuries in amateur players. According to the field position, the programme was effective for defenders and midfielders. In accordance with the type of injury, the exposed group had a lower risk of LAL, biceps femoris and hamstring injuries compared with those in the unexposed group.


#10 Absolute and Relative Training Load and Its Relation to Fatigue in Football
Reference: Front Psychol. 2017 Jun 6;8:878. doi: 10.3389/fpsyg.2017.00878. eCollection 2017.
Authors: Zurutuza U, Castellano J, Echeazarra I, Casamichana D
Summary: The aim of the study was to assess the relationship of external and internal training load (TL) indicators with the objective and subjective fatigue experienced by 15 semi-professional football players, over eight complete weeks of the competition period in the 2015-2016 season, which covered microcycles from 34th to 41st. The maximum heart rate (HRmax) and maximum speed (Vmax) of all the players were previously measured in specific tests. The TL was monitored via questionnaires on rating of perceived exertion (RPE), pulsometers and GPS devices, registering the variables: total distance (TD), player load 2D (PL2D), TD at >80% of the Vmax (TD80), TD in deceleration at < -2 m⋅sec-2 (TDD <-2), TD in acceleration >2 m⋅sec-2 (TDA >2), Edwards (ED), time spent at between 50 and 80% (50-80% HRmax), 80-90% (80-90% HRmax), and >90% of the HRmax (>90% HRmax), and RPE both respiratory/thoracic (RPEres) and leg/muscular (RPEmus). All the variables were analyzed taking into account both the absolute values accumulated over the week and the normalized values in relation to individual mean competition values. Neuromuscular fatigue was measured objectively using the countermovement jump test and subjectively via the Total Quality Recovery (TQR) scale questionnaire. Analytical correlation techniques were later applied within the general linear model. There is a correlation between the fatigue experienced by the player, assessed objectively and subjectively, and the load accumulated over the week, this being assessed in absolute and relative terms. Specifically, the load relative to competition correlated with the physical variables TD (-0.279), PL2D (-0.272), TDD < -2 (-0.294), TDA >2 (-0.309), and sRPEmus (-0.287). The variables related to heart rate produced a higher correlation with TQR. There is a correlation between objectively and subjectively assessed fatigue and the accumulated TL of a player over the week, with a higher sensitivity being shown when compared to the values related to the demands of competition. Monitoring load and assessing fatigue, we are closer to knowing what the prescription of an adequate dose of training should be in order for a player to be as fresh as possible and in top condition for a match. Normalizing training demands with respect to competition could be an appropriate strategy for individualizing player TL.


#11 Effects of structural components of artificial turf on the transmission of impacts in football players
Reference: Sports Biomech. 2017 Feb 24:1-10. doi: 10.1080/14763141.2017.1285347. [Epub ahead of print]
Authors: Encarnacion-Martinez A, Garcia-Gallart A, Gallardo AM, Sanchez-Saez JA, Sanchez-Sanchez J
Summary: The third generation of artificial turf systems (ATS) has matched the mechanical behaviour of natural grass, but today a high heterogeneity at structural level and mechanical behaviour in the new ATS also exists. The objective was to analyse the effect of the structural components of ATS football pitches and running speed on the capacity of impact attenuation. A total of 12 athletes were evaluated at three speed conditions (3.33 m/s, 4 m/s and maximum speed) on four different ATS, classifying them by their components (length of fibre, type of in-fill and sub-base). Impact attenuation was significantly higher in ATS3, characterised by longer fibre compared to other ATS with less fibre length. The ATS4 with a higher length fibre and built on compacted granular material proportioned significantly lower values in the maximum peaks of tibia acceleration. Finally, as speed increases, the peak tibia impacts were significantly higher. Longer fibre length and the capacity to accommodate a higher quantity of infill facilitate higher impact attenuation. Equally, a compacted granular sub-base is related to lower magnitude of maximum tibia peaks. Finally, the magnitude of the tibia acceleration peaks is dependent of running speed for all ATS analysed, being higher as speed increases.


American Football
#1 Brain Network Activation Technology Does Not Assist with Concussion Diagnosis and Return to Play in Football Athletes
Reference: Front Neurol. 2017 Jun 6;8:252. doi: 10.3389/fneur.2017.00252. eCollection 2017.
Authors: Broglio SP, Williams R, Lapointe A, Rettmann A, Moore B, Meehan SK, Eckner JT
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5460056/pdf/fneur-08-00252.pdf
Summary: Concussion diagnosis and management remains a largely subjective process. This investigation sought to evaluate the utility of a novel neuroelectric measure for concussion diagnosis and return to play decision-making. The hypothesis was that Brain Network Activation (BNA) scores obtained within 72-h of injury will be lower than the athlete's preseason evaluation and that of a matched control athlete; and the BNA will demonstrate ongoing declines at the return to play and post-season time points, while standard measures will have returned to pre-injury and control athlete levels. Football athletes with a diagnosed concussion (n = 8) and matched control football athletes (n  = 8) completed a preseason evaluation of cognitive (i.e., Cogstate Computerized Cognitive Assessment Tool) and neuroelectric function (i.e., BNA), clinical reaction time, SCAT3 self-reported symptoms, and quality of life (i.e., Health Behavior Inventory and Satisfaction with Life Scale). Following a diagnosed concussion, injured and control athletes completed post-injury evaluations within 72-h, once asymptomatic, and at the conclusion of the football season. Case analysis of the neuroelectric assessment failed to provide improved diagnostics beyond traditional clinical measures. Statistical analyses indicated significant BNA improvements in the concussed and control groups from baseline to the asymptomatic timepoint. With additional attention being placed on rapid and accurate concussion diagnostics and return to play decision-making, the addition of a novel neuroelectric assessment does not appear to provide additional clinical benefit at this time. Clinicians should continue to follow the recommendations for the clinical management of concussion with the assessment of the symptom, cognitive, and motor control domains.


#2 Cardiovascular disease risk profile of NCAA division III intercollegiate football athletes: a pilot study
Reference: Phys Sportsmed. 2017 Jun 20. doi: 10.1080/00913847.2017.1345288. [Epub ahead of print]
Authors: Wright CJ, Abbey EL, Brandon BA, Reisman EJ, Kirkpatrick CM
Summary: Concerns about the long-term cardiovascular health implications of American football participation have been investigated at the professional and Division I levels, but limited research is available at the less resourced Division III level. Therefore, the objective was to assess the cardiovascular disease risk profile of NCAA Division III intercollegiate football athletes. Eighty-nine varsity football athletes (age=19.6±1.7 years, height=1.81±0.07m, weight=92.7±16.2kg; n=21 linemen, n=68 non-linemen) at a private Division III university volunteered to participate. During a preseason pre-participation physical examination, all participants completed a health history screening form (to assess personal and family history of cardiac related pathologies), and were assessed for height, weight, body mass index (BMI), and blood pressure (BP). Linemen only additionally gave a blood sample for fasting blood glucose and cholesterol analysis, and were assessed for waist and hip circumference, metabolic syndrome, and percent body fat (%BF). These measures were reported as averages and frequencies of elevated cardiovascular. Independent t-tests compared linemen to non-linemen, all other data was presented descriptively. On average, linemen were significantly taller, heavier, had a higher BMI and higher systolic BP than non-linemen (all P<0.05); there was no difference in diastolic BP between the groups (P=0.331). The average anthropometric and cardiac risk characteristics for linemen were largely within normal ranges, however analyzed individually, a substantial number of participants were at elevated risk (BMI ≥30=85.7%, %BF ≥25=71.4%, waist circumference ≥1=42.9%, hypertension=9.5%, high density lipoproteins <40mg/dL=42.9%, and triglycerides ≥150mg/dL=6.7%; metabolic syndrome prevalence=19%). Similar to research in elite athletics, linemen at a single Division III university have elevated cardiovascular disease risk. Physicians and other healthcare providers should consider this elevated risk during pre-participation physical examinations and in planning educational or dietary programming targeted to promoting cardiovascular health.


#3 Effects of turf and cleat footwear on plantar load distributions in adolescent American football players during resisted pushing
Reference: Sports Biomech. 2017 Feb 28:1-11. doi: 10.1080/14763141.2016.1271448. [Epub ahead of print]
Authors: Taylor JB, Nguyen AD, Griffin JR, Ford KR
Summary: Metatarsal and midfoot injuries are common in American football. Footwear design may influence injury rates by altering plantar foot loading patterns in these regions. The purpose of this study was to determine the effect of cleat design on in-shoe plantar foot loading during a football-specific, resisted pushing task. Twenty competitive football players (age 14.7 ± 1.8 years, height 1.72 ± 0.10 m, and mass 71.8 ± 26.9 kg) completed three trials of pushing a weighted sled at maximal effort in a standard shoe (CLEAT) and artificial turf-specific shoe (TURF), with flexible in-shoe force measuring insoles. Repeated measures ANOVAs identified mean differences in maximum force and relative load under all regions of the foot. Results showed higher forces in the CLEAT under the medial (p < 0.001) and lateral (p = 0.004) midfoot, central (p = 0.007) and lateral (p < 0.001) forefoot, and lesser toes (p = 0.01), but lower forces in the hallux (p = 0.02) compared to the TURF shoe. Additionally, relative loading was higher in the CLEAT under the medial (p < 0.001) and lateral (p = 0.002) midfoot and lateral (p < 0.001) forefoot, but lower in the medial forefoot (p = 0.006) and hallux (p < 0.001) compared to the TURF shoe. The two shoes elicited distinct plantar loading profiles and may influence shoe selection decisions during injury prevention or rehabilitation practices.


Australian Football
#1 Preseason Workload Volume and High-Risk Periods for Noncontact Injury Across Multiple Australian Football League Seasons
Reference: J Strength Cond Res. 2017 Jul;31(7):1821-1829. doi: 10.1519/JSC.0000000000001669.
Authors: Colby MJ, Dawson B, Heasman J, Rogalski B, Rosenberg M, Lester L, Peeling P.
Summary: The purpose of this study was to assess the association between preseason workloads and noncontact injury risk in Australian football players. Individual player injury data were recorded over 4 full seasons (2012-15) from one professional club. Noncontact injury incidence (per 1,000 "on legs" field training and game hours) was compared across the preseason, precompetition, and in-season phases to determine relative noncontact injury risk. Preseason workloads (global positioning system-derived total distance run and sprint distance) and individual (fixed) injury risk factors (age, previous injury history) were incorporated into the analysis. A generalized estimating equation with a binary logistic function modeled potential risk factors with noncontact injury for selected periods across the annual cycle. Odds ratios were calculated to determine the relative injury risk. The (preseason) precompetition phase (19.1 injuries per 1,000 hours) and (in-season) rounds 12-17 (16.0 injuries per 1,000 hours) resulted in the highest injury incidence. Low cumulative total distances in late preseason (<108 km) and precompetition (76-88 km) periods were associated with significantly (p ≤ 0.05) greater injury risk during the in-season phase. In conclusion, these results suggest players are at the greatest injury risk during the precompetition period, with low preseason cumulative workloads associated with increased in-season injury risk. Therefore, strength and conditioning staff should place particular emphasis on achieving at least moderate training loads during and leading into this phase, where competitive game play is first introduced.


#2 Interchange rotation factors and player characteristics influence physical and technical performance in professional Australian Rules football
Reference: J Sci Med Sport. 2017 Jun 8. pii: S1440-2440(17)30455-3. doi: 10.1016/j.jsams.2017.06.008. [Epub ahead of print]
Authors: Dillon PA, Kempton T, Ryan S, Hocking J, Coutts AJ
Summary: The purpose was to examine the effects of match-related and individual player characteristics on activity profile and technical performance during rotations in professional Australian football. Global positioning system data and player rating scores were collected from 33 professional Australian football players during 15 Australian football League matches. Player rating scores were time aligned with their relative total and high-speed running (HSR) distance (>20kmh-1) for each on ground rotation. Individual players' maximal aerobic running speed (MAS) was determined from a two-kilometre trial. A multilevel linear mixed model was used to examine the influence of rotations on physical activity profiles and skill execution during match play. Rotation duration and accumulated distance resulted in a trivial-to-moderate reduction in relative total and HSR distances as well as relative rating points. The number of disposals in a rotation had a small positive effect on relative total and HSR distances and a large positive effect on relative rating points. MAS was associated with a moderate-to-large increase in relative total distance, but had a large negative effect on relative rating points. Previous rotation time, stoppages and the number of rotations in the quarter had a trivial-to-small negative effect on relative total and HSR distances. A greater speed (mmin-1) was associated with a trivial increase in rating points during a rotation, while there was a trivial decrease in relative total distance as rating points increased. The complex relationship between factors that influence activity profile and technical performance during rotations in Australian football needs to be considered when interpreting match performance.


Gaelic Football
#1 Physiological Profile and Activity Pattern of Minor Gaelic Football Players
Reference: J Strength Cond Res. 2017 Jul;31(7):1811-1820. doi: 10.1519/JSC.0000000000001667.
Authors: Cullen BD, Roantree MT, McCarren AL, Kelly DT, OʼConnor PL, Hughes SM, Daly PG, Moyna NM.
Summary: The purpose of this study was to evaluate the physiological profile and activity pattern in club- and county-level under-18 (U-18) Gaelic football players relative to playing position. Participants (n = 85) were analyzed during 17 official 15-a-side matches using global positioning system technology (SPI Pro X II; GPSports Systems, Canberra, Australia) and heart rate (HR) telemetry. During the second part of this study, 63 participants underwent an incremental treadmill test to assess their maximal oxygen uptake (V[Combining Dot Above]o2max) and peak HR (HRmax). Players covered a mean distance of 5,774 ± 737 m during a full 60-minute match. The mean %HRmax and %V[Combining Dot Above]O2max observed during the match play were 81.6 ± 4.3% and 70.1 ± 7.75%, respectively. The playing level had no effect on the distance covered, player movement patterns, or %HRmax observed during match play. Midfield players covered significantly greater distance than defenders (p = 0.033). Playing position had no effect on %HRmax or the frequency of sprinting or high-intensity running during match play. The frequency of jogging, cruise running, striding (p = 0.000), and walking (p = 0.003) was greater in the midfield position than in the forward position. Time had a significant effect (F(1,39) = 33.512, p-value = 0.000, and (Equation is included in full-text article.)= 0.462) on distance covered and %HRmax, both of which showed a reduction between playing periods. Gaelic football is predominantly characterized by low-to-moderate intensity activity interspersed with periods of high-intensity running. The information provided may be used as a framework for coaches in the design and prescription of training strategies. Positional specific training may be warranted given the comparatively greater demands observed in the midfield playing position. Replicating the demands of match play in training may reduce the decline in distance covered and %HRmax observed during the second half of match play.

Wed

05

Jul

2017

World Conference on Science and Soccer - Presentations Day 3 Part II

The following slides were presented on Day 3.

 

Sebastien Sangnier

John Fitzpatrick

Donna O'Connor

Andy Abraham

Daniel Leyhr

 

....and then there was the closing ceremony. The next World Congress on Science and Football (will be the next World Conference on Science and Soccer and therefore not only cover soccer, but all football codes, therefore also Australian Rules, Rugby, Gaelic football, American Football) will be held in Melbourne in 2019. If you want some information (when the time is right) I suggest you follow @WCSF_2019 to get updates.

 

Fri

30

Jun

2017

Latest research in football - week 24 - 2017

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Gender-related cardiac dimension differences between female and male professional soccer players
Reference: J Sports Med Phys Fitness. 2017 Jun 8. doi: 10.23736/S0022-4707.17.07422-9. [Epub ahead of print]
Authors: Sansonio de Morais A, Assuncao Ferreira G, Lima-Silva AE, Gomes Filho A
Summary: The aim of this study was to determine if cardiac hypertrophy differs between professional female and male soccer players. Twenty-two female and 20 male professional soccer players, and their respective non-athlete controls (22 females and 19 males) were submitted to an echocardiogram. Females had a shorter left ventricular intracavitary diameter and wall thicknesses than males in both groups. However, these differences disappeared when cardiac dimensions were expressed relative to body mass area (p > 0.05). Compared to their respective controls, female and male soccer players had a longer (p < 0.05) left ventricular end-systolic diameter (female: 1.87 ± 0.16 vs. 1.77 ± 0.15 cm/m2 and male: 1.83 ± 0.21 vs. 1.73 ± 0.16 cm/m2), left ventricular end-diastolic diameter (female: 2.86 ± 0.25 vs. 2.74 ± 0.22 cm/m2 and male: 2.81 ± 0.26 vs. 2.55 ± 0.66 cm/m2), left ventricular posterior wall thickness (female: 0.44 ± 0.06 vs. 0.39 ± 0.04 cm/m2 and male: 0.43 ± 0.04 vs. 0.39 ± 0.10 cm/m2), left ventricular septal wall thickness (female: 0.47 ± 0.06 vs. 0.41 ± 0.04 cm/m2 and male: 0.45 ± 0.04 vs. 0.40 ± 0.11 cm/m2), and left ventricular mass index (female: 91.8 ± 22.1 vs. 72.3 ± 10.5 g/m2 and male: 121.7 ± 20.3 vs. 99.8 ± 13.8 g/m2 ). Part of the gender differences in cardiac dimensions might be attributed to differences in body dimension. Soccer training increases cardiac dimensions even with BSA correction and females seem to have similar left ventricle remodeling compared to males.


#2 Comparison of the movement patterns between small- and large-side games training and competition in professional soccer players
Reference: J Sports Med Phys Fitness. 2017 Jun 8. doi: 10.23736/S0022-4707.17.07343-1. [Epub ahead of print]
Authors: Gimenez JV, Del-Coso J, Leicht AS, Gomez MA
Summary: The purpose of this investigation was to compare the movement patterns of professional soccer players during a small-sided game (SSG), a large-sided game (LSG) and a competitive friendly match (FM). Fourteen professional players participated in three training routines with a similar relative pitch area per player. The SSG and LSG consisted of 8 repetitions of 4-min game play, interspersed by 2-min of active recovery, and their data were compared to the first 32 minutes of a FM. All movement patterns from walking to sprint running were recorded using 10Hz GPS devices while player perception of exertion was recorded via visual analogue scale, post-trial. Total running distance (3852±405 vs. 3359±429 and 3088 ± 414 m), running distance at 5-6.9 m/s (222±98 vs. 75±53 and 49±35 m) and maximal running speed (7.0±0.7 vs. 6.1±0.4 and 6.0±0.7 m/s) were significantly greater during FM than for SSG and LSG. However, the number of accelerations (462±16 vs. 458±12 vs. 422±15) and decelerations (733±31 vs. 692 ±24 vs. 609±27), and the rating of perceived exertion (8±1 vs. 7±1 vs. 5±1) were significantly greater during SSG compared to LSG and FM. Although smaller game-based training routines do not replicate exactly the movement patterns of a competitive match, they can increase the execution of short-term and high-intensity movements for specialised training in professional soccer players.


#3 High-speed running and sprinting as an injury risk factor in soccer: Can well-developed physical qualities reduce the risk?
Reference: J Sci Med Sport. 2017 May 25. pii: S1440-2440(17)30442-5. doi: 10.1016/j.jsams.2017.05.016. [Epub ahead of print]
Authors: Malone S, Owen A, Mendes B2, Hughes B, Collins K, Gabbett TJ
Summary: This study investigated the association between high-speed running (HSR) and sprint running (SR) and injuries within elite soccer players. The impact of intermittent aerobic fitness as measured by the end speed of the 30-15 intermittent fitness test (30-15VIFT) and high chronic workloads (average 21-day) as potential mediators of injury risk were also investigated. 37 elite soccer players from one elite squad were involved in a one-season study. Training and game workloads (session-RPE×duration) were recorded in conjunction with external training loads (using global positioning system technology) to measure the HSR (>14.4kmh-1) and SR (>19.8kmh-1) distance covered across weekly periods during the season. Lower limb injuries were also recorded. Training load and GPS data were modelled against injury data using logistic regression. Odds ratios (OR) were calculated with 90% confidence intervals based on 21-day chronic training load status (sRPE), aerobic fitness, HSR and SR distance with these reported against a reference group. Players who completed moderate HSR (701-750-m: OR: 0.12, 90%CI: 0.08-0.94) and SR distances (201-350-m: OR: 0.54, 90%CI: 0.41-0.85) were at reduced injury risk compared to low HSR (≤674-m) and SR (≤165-m) reference groups. Injury risk was higher for players who experienced large weekly changes in HSR (351-455-m; OR: 3.02; 90%CI: 2.03-5.18) and SR distances (between 75-105-m; OR: 6.12, 90%CI: 4.66-8.29). Players who exerted higher chronic training loads (≥2584 AU) were at significantly reduced risk of injury when they covered 1-weekly HSR distances of 701-750m compared to the reference group of <674m (OR=0.65, 90% CI 0.27-0.89). When intermittent aerobic fitness was considered based on 30-15VIFT performance, players with poor aerobic fitness had a greater risk of injury than players with better-developed aerobic fitness. Exposing players to large and rapid increases in HSR and SR distances increased the odds of injury. However, higher chronic training loads (≥2584 AU) and better intermittent aerobic fitness off-set lower limb injury risk associated with these running distances in elite soccer players.


#4 The match-to-match variation of match-running in elite female soccer
Reference: J Sci Med Sport. 2017 May 25. pii: S1440-2440(17)30435-8. doi: 10.1016/j.jsams.2017.05.009. [Epub ahead of print]
Authors: Trewin J, Meylan C, Varley MC, Cronin J
Summary: The purpose of this study was to examine the match-to-match variation of match-running in elite female soccer players utilising GPS, using full-match and rolling period analyses. Elite female soccer players (n=45) from the same national team were observed during 55 international fixtures across 5 years (2012-2016). Data was analysed using a custom built MS Excel spreadsheet as full-matches and using a rolling 5-min analysis period, for all players who played 90-min matches (files=172). Variation was examined using co-efficient of variation and 90% confidence limits, calculated following log transformation. Total distance per minute exhibited the smallest variation when both the full-match and peak 5-min running periods were examined (CV=6.8-7.2%). Sprint-efforts were the most variable during a full-match (CV=53%), whilst high-speed running per minute exhibited the greatest variation in the post-peak 5-min period (CV=143%). Peak running periods were observed as slightly more variable than full-match analyses, with the post-peak period very-highly variable. Variability of accelerations (CV=17%) and Player Load (CV=14%) was lower than that of high-speed actions. Positional differences were also present, with centre backs exhibiting the greatest variation in high-speed movements (CV=41-65%). Practitioners and researchers should account for within player variability when examining match performances. Identification of peak running periods should be used to assist worst case scenarios. Whilst micro-sensor technology should be further examined as to its viable use within match-analyses.


#5 Changes in sprint-related outcomes during a period of systematic training in a girls' soccer academy
Reference: J Strength Cond Res. 2017 Jun 8. doi: 10.1519/JSC.0000000000002055. [Epub ahead of print]
Authors: Wright MD, Atkinson G
Summary: Longitudinal data tracking performance indicators collected during structured training are lacking in young female soccer players. Therefore, changes in 5-m acceleration, 20-m speed, change-of-direction speed and repeated-sprint ability were quantified during a three-year period in an FA Centre of Excellence. Fourteen players (mean age = 12.1 years, SD = ±0.9) were recruited and their best performance scores from pre-season and in-season testing were averaged. Players were typically exposed to soccer (2 x 90 min per week) and strength and conditioning training (1 x 70 min per week) and played 20 soccer matches (50-80 min) during 35-week seasons. Mean (±90%CL) overall improvements over the three years were 5.9% (1.3) (most likely large) for speed, 4.0% (1.0) (most likely large) for repeated-sprint ability, 8.8% (1.1) for acceleration and 8.3% (1.4) for change-of-direction speed (both most likely very large). Improvements between years one and two ranged from most likely moderate to very large. Further small improvements in change-of-direction speed and 20-m speed (both likely) were observed between years two and three. Individual differences in response were apparent only for change-of-direction speed, which were moderate and small between years two and three. Most likely very large to near perfect within-player correlations were observed between maturation and sprint measures. These data from a single-arm longitudinal study indicate that systematic exposure to training, which includes one dedicated strength and conditioning session each week, is associated with improvements in sprint related physical qualities in girls.


#6 Distinguishing Playing Status Through a Functionally Relevant Performance Measure in Female Division I Collegiate Soccer Athletes
Reference: J Strength Cond Res. 2017 Jun 8. doi: 10.1519/JSC.0000000000002053. [Epub ahead of print]
Authors: Magrini MA, Colquhoun RJ, Sellers JH, Conchola EC, Hester GM, Thiele RM, Pope ZK, Smith DB
Summary: Although soccer is predominately an endurance sport, high velocity movements may be an important indicator of athletic success. The purpose of this investigation was to establish whether squat jumps (SJ) can differentiate starters from non-starters with a female collegiate division I soccer team. Eighteen female division I soccer athletes were separated into two groups: 9 starters (age: 19.5 ± 1.0; mass = 64.8 ± 11.5 kg; height = 167.5 ± 7.7 cm; games started = 18.2 ± 4.7; minutes played = 1633.8 ± 478.2 min) and 9 non-starters (age: 19.4 ± 1.4 years; mass = 63.3 ± 4.2 kg; height = 164.7 ± 6.8 cm; games started 0.7 ± 1.3; minutes played 158.2 ± 269.3). Each athlete performed 3 maximal SJs at a starting knee angle of 110° without arm swing. Each participant's SJ height, mean power (MP), peak power (PP), mean velocity (MV), and peak velocity (PV) were measured during each attempt by a linear position transducer (LPT). No statistically significant differences (p ≥ 0.05) in MP and PP between the starters and non-starters were observed. However, starters performed significantly better than non-starters in SJ height (p = 0.002), MV (p = 0.025), and PV (p = 0.015). Additionally, SJ height was strongly correlated with MV (r = 0.628) and PV (r = 0.647). These findings suggest that SJ height, MV and PV, may be important variables for discriminating differences between starters and non-starters in division I female soccer athletes and a strong indicator of explosive performance.


#7 Cameroonian professional soccer players and risk of atherosclerosis
Reference: BMC Res Notes. 2017 Jun 2;10(1):186. doi: 10.1186/s13104-017-2508-x.
Authors: Nansseu JR, Ama Moor VJ, Takam RDM, Zing-Awona B, Azabji-Kenfack M, Tankeu F, Tchoula CM, Moukette BM, Ngogang JY
Summary: Elevated titers of antibodies against oxidized low-density lipoproteins-cholesterol (ox-LDL-Ab) have been reported among professional athletes, paradoxically reflecting an increased risk of developing atherogenic and/or cardiovascular events. This study aimed to determine titers of ox-LDL-Ab in a group of Cameroonian professional soccer players, and evaluate their evolution during part of a competition season as well as the plasmatic antioxidant status to find out if this latter correlates with ox-LDL-Ab . We conducted a descriptive cohort study in 2012 including 18 healthy male soccer players. Three samplings were performed in March (T1), May (T2), and July 2012 (T3) to assess the lipid profile, titers of ox-LDL-Ab, and plasmatic concentrations of four antioxidants: the ferric reducing antioxidant power (FRAP), reduced glutathione (GSH), superoxide dismutase (SOD), and uric acid. Ages ranged from 16 to 28 years with a median (interquartile range) of 19.5 (19-23) years. Total cholesterol, high-density lipoproteins-cholesterol (HDL-C), low-density lipoproteins-cholesterol (LDL-C) and triglycerides varied within normal ranges throughout the three samplings. While total cholesterol and LDL-C titers increased significantly (p = 0.003 and p = 0.006, respectively), triglycerides and HDL-C values varied non-significantly throughout the measurements (p = 0.061 and p = 0.192, respectively). The median ox-LDL-Ab titers were respectively: 653.3 (468.2-838.8) mIU/ml at T1, 777.7 (553.7-1150.7) mIU/ml at T2, and 1037.7 (901.7-1481.5) mIU/ml at T3. Overall, ox-LDL-Ab titers increased significantly from T1 to T3 (p = 0.006). Concomitantly, uric acid and FRAP concentrations decreased significantly (p = 0.001 and p = 0.003, respectively); on the contrary, GSH and SOD values increased, but insignificantly (p = 0.115 and p = 0.110, respectively). There was a positive and significant correlation between ox-LDL-Ab and HDL-C (ρ = 0.519, p = 0.027), and between ox-LDL-Ab and SOD (ρ = 0.504, p = 0.033) at T2. Ox-LDL-Ab values were expected to increase with each new visit (β = 201.1; p = 0.041) and each IU/ml of SOD titers (β = 23.6; p = 0.019). These Cameroonian professional soccer players exhibited high levels of ox-LDL-Ab reflecting elevated levels of oxidatively-modified LDL-C particles with an increment over time, this being insufficiently counterbalanced by the antioxidant defense mechanisms. As a consequence, they may be at increased atherogenic and cardiovascular risks.


#8 How Do Soccer Players Adjust Their Activity in Team Coordination? An Enactive Phenomenological Analysis
Reference: Front Psychol. 2017 May 26;8:854. doi: 10.3389/fpsyg.2017.00854. eCollection 2017.
Authors: Gesbert V, Durny A, Hauw D
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5445190/pdf/fpsyg-08-00854.pdf
Summary: This study examined how individual team members adjust their activity to the needs for collective behavior. To do so, we used an enactive phenomenological approach and explored how soccer players' lived experiences were linked to the active regulation of team coordination during eight offensive transition situations. These situations were defined by the shift from defensive to offensive play following a change in ball possession. We collected phenomenological data, which were processed in four steps. First, we reconstructed the diachronic and synchronic dynamics of the players' lived experiences across these situations in order to identify the units of their activity. Second, we connected each player's units of activity side-by-side in chronological order in order to identify the collective units. Each connection was viewed as a collective regulation mode corresponding to which and how individual units were linked at a given moment. Third, we clustered each collective unit using the related objectives within three modes of regulation-local (L), global (G), and mixed (M). Fourth, we compared the occurrences of these modes in relation to the observable key moments in the situations in order to identify typical patterns. The results indicated four patterns of collective regulation modes. Two distinct patterns were identified without ball possession: reorganize the play formation (G and M) and adapt to the actions of putting pressure on the ball carrier (M). Once the ball was recovered, two additional patterns emerged: be available to get the ball out of the recovery zone (L) and shoot for the goal (L and M). These results suggest that team coordination is a fluctuating phenomenon that can be described through the more or less predictable chaining between these patterns. They also highlight that team coordination is supported by several modes of regulation, including our proposal of a new mode of interpersonal regulation. We conclude that future research should investigate the effect of training on the enaction of this mode in competition.


#9 Emergency response facilities including primary and secondary prevention strategies across 79 professional football clubs in England
Reference: Br J Sports Med. 2017 Jun 14. pii: bjsports-2016-097440. doi: 10.1136/bjsports-2016-097440. [Epub ahead of print]
Authors: Malhotra A, Dhutia H, Gati S, Yeo TJ, Finnochiaro G, Keteepe-Arachi T, Richards T, Walker M, Birt R, Stuckey D, Robinson L, Tome M, Beasley I, Papadakis M, Sharma S
Summary: The aim was to assess the emergency response planning and prevention strategies for sudden cardiac arrest (SCA) across a wide range of professional football clubs in England. A written survey was sent to all professional clubs in the English football league, namely the Premiership, Championship, League 1 and League 2. Outcomes included: (1) number of clubs performing cardiac screening and frequency of screening; (2) emergency planning and documentation; (3) automated external defibrillator (AED) training and availability; and (4) provision of emergency services at sporting venues. 79 clubs (86%) responded to the survey. 100% clubs participated in cardiac screening. All clubs had AEDs available on match days and during training sessions. 100% Premiership clubs provided AED training to designated staff. In contrast, 30% of lower division clubs with AEDs available did not provide formal training. Most clubs (n=66; 83%) reported the existence of an emergency action plan for SCA but formal documentation was variable. All clubs in the Premiership and League 1 provided an ambulance equipped for medical emergencies on match days compared with 75% of clubs in the Championship and 66% in League 2. The majority of football clubs in England have satisfactory prevention strategies and emergency response planning in line with European recommendations. Additional improvements such as increasing awareness of European guidelines for emergency planning, AED training and mentorship with financial support to lower division clubs are necessary to further enhance cardiovascular safety of athletes and spectators and close the gap between the highest and lower divisions.


#10 Validity of heart rate-based indices to measure training load and intensity in elite football players
Reference: J Strength Cond Res. 2017 Jun 12. doi: 10.1519/JSC.0000000000002057. [Epub ahead of print]
Authors: Silva P, Santos ED, Grishin M, Rocha JM
Summary: This study aimed to identify the most sensible heart rate-based indices to physical measures of training load and intensity. Twenty professional football players competing in the Russian league and in the UEFA Champions League were monitored during 15 training sessions (270 individual records) using GPS devices (10 Hz) and heart rate telemetry. Expert knowledge and a collinearity r < .5 were used initially to select the external physical markers for the final analysis. A multivariate-adjusted within-subjects model was employed to quantify the correlations between heart rate indices with various measures of training intensity and load. The number of accelerations > 2.5 m/s and the number of high intensity bursts remained in the final multivariate model for training load. The adjusted correlations with Banister's TRIMP were r = .49 and r = .3, respectively. For training intensity, the same previous variables expressed as per minute plus the volume of high speed running per minute remained in the final model. The adjusted correlations with the percentage of time spent above 80% of individual maximum heart rate (tHR80%) were, in the same order, r = .3, r = .22 and r = .18. The results of this study demonstrate the validity of TRIMP and tHR80% as measures of training load and intensity, respectively, and identified accelerations and high intensity repeated efforts (high intensity bursts) as being moderately predictive of heart rate responses.


#11 Federation Internationale de Football Association (FIFA) 2014 World Cup Impact on Hospital-Treated Suicide Attempt (Overdose) in Tehran
Reference: Suicide Life Threat Behav. 2017 Jun 13. doi: 10.1111/sltb.12359. [Epub ahead of print]
Authors: Hassanian-Moghaddam H, Ghorbani F, Rahimi A, Farahani TF, Sani PSV, Lewin TJ, Carter GL
Summary: Social influences on suicidal behaviors may be important but are less frequently studied than the influences of mental illness, physical illness, and demographic variables. Major international sporting events may have an impact on suicidal behaviors at the national and local level, an effect possibly mediated by gender and age. We examined the association of hospital-treated deliberate self-poisoning episodes (by gender and by age) in Tehran: before, during, and after the 2014 FIFA World Cup held in Brazil, in which the Iranian national team participated and was eliminated after the pool games. We used a time series analysis within an autoregressive integrated moving average model and found a significant increase in hospital-treated deliberate self-poisoning during the 4-week period of the 2014 FIFA World Cup in Brazil in females but a nonsignificant increase in males. A significant increase was also seen in the youngest age group (12-20 years), but not in the two older age groups. If the effects of nonsuccess at major international sporting events could be shown to have a potential harmful effect on aggregate local or national rates of suicidal behaviors, the possibility of preventative interventions and preemptive additional service provision could be planned in advance of these events.



American Football
#1 A Season of American Football is not Associated with Changes in Plasma Tau
Reference: J Neurotrauma. 2017 Jun 14. doi: 10.1089/neu.2017.5064. [Epub ahead of print]
Authors: Oliver J, Jones M, Anzalone A, Kirk M, Gable D, Repshas J, Johnson T, Hogland K, Blennow K, Zetterberg H
Summary: American football athletes are routinely exposed to sub-concussive impacts over the course of the season. This study sought to examine the effect of a season of American football on plasma tau, a potential marker of axonal damage. Nineteen (n =19) National Collegiate Association (NCAA) American football athletes underwent serial blood sampling over the course of the 2014-2015 season at those times in which the number and magnitude of head impacts likely changed. Non-contact, sport-control, NCAA men's swim athletes (n=19) provided a single plasma sample for comparison. No significant differences were observed between control swim athletes and American football athletes following a period of non-contact (p = 0.569) or a period of contact (p = 0.076). Those American football athletes categorized as starters (n=11) had higher tau concentrations than non-starters (n=8) following a period of non-contact (p = 0.039) and contact (p = 0.036), but not higher than swimmers (p = 1.000 and p = 1.000, respectively). No difference was noted over the course of the season in American football athletes irrespective of starter status. Despite routine head impacts, common to the sport of American football, no changes were observed over the course of the season in American football athletes, irrespective of starter status. Further, no difference was observed between American football athletes and non-contact control swim athletes following a period of non-contact or contact. These data suggest that plasma tau is not sensitive enough to detect damage associated with repetitive sub-concussive impacts sustained by collegiate level American football athletes.



Australian Football
#1 Identifying high risk loading conditions for in-season injury in elite Australian football players
Reference: J Sci Med Sport. 2017 May 25. pii: S1440-2440(17)30438-3. doi: 10.1016/j.jsams.2017.05.012. [Epub ahead of print]
Authors: Stares J, Dawson B, Peeling P, Heasman J, Rogalski B, Drew M, Colby M, Dupont G, Lester L
Summary: The purpose was to examine different timeframes for calculating acute to chronic workload ratio (ACWR) and whether this variable is associated with intrinsic injury risk in elite Australian football players. Internal (session rating of perceived exertion: sRPE) and external (GPS distance and sprint distance) workload and injury data were collected from 70 players from one AFL club over 4 seasons. Various acute (1-2 weeks) and chronic (3-8 weeks) timeframes were used to calculate ACWRs: these and chronic load categories were then analysed to determine the injury risk in the subsequent month. Poisson regression with robust errors within a generalised estimating equation were utilised to determine incidence rate ratios (IRR). Altering acute and/or chronic timeframes did not improve the ability to detect high injury risk conditions above the commonly used 1:4 week ACWR. Twenty-seven ACWR/chronic load combinations were found to be "high risk conditions" (IRR>1, p<0.05) for injury within 7 days. Most (93%) of these conditions occurred when chronic load was low or very low and ACWR was either low (<0.6) or high (>1.5). Once a high injury risk condition was entered, the elevated risk persisted for up to 28 days. Injury risk was greatest when chronic load was low and ACWR was either low or high. This heightened risk remained for up to 4 weeks. There was no improvement in the ability to identify high injury risk situations by altering acute or chronic time periods from 1:4 weeks.

Tue

27

Jun

2017

Latest research in football - week 23 - 2017

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 The Effect of a Simulated Soccer Match on Anterior Cruciate Ligament Injury Risk Factors
Reference: Int J Sports Med. 2017 Jun 2. doi: 10.1055/s-0043-109238. [Epub ahead of print]
Authors: Wright M, Chesterton P, Wijnbergen M, O'Rourke A, Macpherson T
Summary: The purpose was to investigate the effect of within match fatigue on knee kinematics and jump kinetics in girls' soccer players, a quasi-experiment time series design was employed collecting data before, after and at 15-min intervals during a 90-min simulated soccer match. 15 girl players (age 13.1±1.4 years) performed a counter movement jump and a single-leg drop jump. Mean concentric force and flight time to contraction time ratio were derived from the counter movement jump. Knee valgus and flexion angles were calculated during the single-leg drop from 3-dimensional motion capture. Subjective ratings of perceived exertion (RPE) and readiness were collected at each time series. Small to large increases in RPE and reductions in readiness were observed throughout the match from baseline. Moderate to large improvements in mean concentric force were shown at 15, 75 and 90-min when compared to baseline. Flight time to contraction time ratio increased moderately at 15 min. Changes in kinematics were typically trivial or unclear however, small increases in knee valgus were shown after 30 min compared to baseline. Subjective measures may provide useful information to understand the physical response of young players to match play.


#2 Perceptions of the Coach-Athlete Relationship Predict the Attainment of Mastery Achievement Goals Six Months Later: A Two-Wave Longitudinal Study among F. A. Premier League Academy Soccer Players
Reference:  Front Psychol. 2017 May 18;8:684. doi: 10.3389/fpsyg.2017.00684. eCollection 2017.
Authors: Nicholls AR, Earle K, Earle F, Madigan DJ
Summary: All football teams that compete within the F. A. Premier League possess an academy, whose objective is to produce more and better home-grown players that are capable of playing professionally. These young players spend a large amount of time with their coach, but little is known about player's perception of the coach-athlete relationship within F. A. Premier League Academies. The objectives of this study were to examine whether perceptions of the coach-athlete relationship changed over six months and if the coach-athlete relationship predicted self-reported goal achievement among F. A. Premier League academy players. This study included cross-sectional (n = 104) and longitudinal (n = 52) assessments, in which academy soccer players completed a measure of the coach-athlete relationship and goal achievement across either one or two time periods. The cross-sectional data were subjected to bivariate correlations, whereas the longitudinal data were analyzed using multiple regressions. Perceptions of the coach-athlete relationship remained stable over time. The coach-athlete relationship predicted the achievement of mastery goals six months later. Enhancing the quality of the coach-athlete relationship among elite adolescent athletes appears to be a suitable way of maximizing mastery achievement goals, particularly among developmental athletes who participate in team sports.


#3 Soccer small-sided games in young players: rule modification to induce higher physiological responses
Reference: Biol Sport. 2017 Jun;34(2):163-168. doi: 10.5114/biolsport.2017.64590. Epub 2017 Jan 1.
Authors: Halouani J, Chtourou H, Dellal A, Chaouachi A, Chamari K
Summary: The aim of this study was to identify the physiological responses of 3 forms of players' numbers during two different games rules of small-sided games (SSG: stop-ball vs. small-goals rules). Eighteen youth amateur soccer players (age 13.5±0.7 years; height 168.9±6.1cm; body mass 63.1±7.7 kg) participated in this study and performed 3 SSGs with varying players' number (2vs.2; 3vs.3 and 4vs.4): stop-ball SSG (SB-SSG) vs. small-goals SSG (SG-SSG) in a randomized and counter-balanced order on a constant pitch dimension (20×25m). The players performed 4×4 min SSG with 2-min of passive recovery in-between. Heart rate (HR), (expressed in bpm and % HRmax), lactate ([La-]), and rating of perceived exertion (RPE) were collected during each session. SB-SSG induced the higher HR values in comparison with the SG-SSG for the 3 game formats (2vs.2; 3vs.3 and 4vs.4). Also, compared with SG-SSG, SB-SSG induced the higher HR values during 2vs.2 compared with 4vs.4 games rules (178 vs. 174 and 175 vs. 171 bpm, respectively). However, the SB-SSG was more intense compared with SG-SSG in the 2 vs. 2 game rule compared with the two others (3 vs.3 and 4 vs. 4) for [La-] and RPE (7.58 vs. 7; 7.25 vs. 6.75 and 6.5 vs. 6.16 mmol ∙ L-1, and 7.75 vs. 7.33; 7.41 vs. 7.08 and 7.16 vs. 6.83, respectively). Therefore, the use of 2 vs. 2 and 3 vs. 3 SSG with SB-SSG seems to represent an alternative to coaches to increase cardiovascular and metabolic demands in youth soccer players.


#4 In-season training periodization of professional soccer players
Reference: Biol Sport. 2017 Jun;34(2):149-155. doi: 10.5114/biolsport.2017.64588. Epub 2017 Jan 1.
Authors: Los Arcos A, Mendez-Villanueva A, Martinez-Santos R
Summary: The aim of this study was to quantify the seasonal perceived respiratory and muscular training loads (i.e., sRPEres-TL and sRPEmus-TL) completed by elite-oriented young professional soccer players. Twenty-four players (20.3 ± 2.0 years) belonging to the same reserve team of a Spanish La Liga club participated in this study. Only the players that were available to train for a whole week with the team and also to play the weekly game were considered: Starters, players that participated in the match for at least 45 min and Non-Starters, players that did not participate or played less than 45 minutes in the match. The competitive period was analysed after the division into 5x6-8 week blocks and 35x1 week microcycles. Data were also analysed with respect to number of days before the immediate match. Weekly TL variation across the in-season blocks was trivial-small for both groups except between Block 2 and Block 3 (ES= moderate). Substantial TL differences (ES= small-very likely) were found between training days, the TL pattern being a progressive increase up to MD-3 followed by a decrease until MD-1. Except for the match, sRPEres-/sRPEmus-TL was very similar between Starters and Non-Starters. In summary, perceived TL across the season displayed limited variation. Coaches periodized training contents to attain the highest weekly TL 72 hours before the match to progressively unload the players between MD-3 and the match day. The data revealed that the TL arising from the weekly game was solely responsible for the observed higher weekly TL of Starters in comparison with Non-Starters.


#5 Specific physical trainability in elite young soccer players: efficiency over 6 weeks' in-season training
Reference: Biol Sport. 2017 Jun;34(2):137-148. doi: 10.5114/biolsport.2017.64587. Epub 2017 Jan 1.
Authors: Chtara M, Rouissi M, Haddad M, Chtara H, Chaalali A, Owen A, Chamari K
Summary: The aim of the present study was to compare the effects of 3 training protocols (plyometric [PLYO], agility [AG], or repeated shuttle sprints [RS]) on physical performance in the same population of young soccer players. Forty-two youth-level male players (13.6±0.3-years; 1.65±0.07 m; 54.1±6.5 kg; body fat: 12.8±2.6%) participated in a short-term (6-week) randomized parallel fully controlled training study (pre-to-post measurements): PLYO group, n=10; AG group, n=10; RS group, n=12; and control group [CON] n=10. PLYO training = 9 lower limb exercises (2-3 sets of 8-12 repetitions). The AG group performed planned AG drills and direction changes. RS training consisted of 2-4 sets of 5-6x 20 to 30 m shuttle sprints (20 seconds recovery in between). Progressive overload principles were incorporated into the programme by increasing the number of foot contacts and varying the complexity of the exercises. Pre/post-training tests were: bilateral standing horizontal jump, and unilateral horizontal jumps, sprint (30 m with 10 m lap time), agility (20 m zigzag), and repeated sprint ability (RSA) (i.e. 6x30 m shuttle sprints: 2x15 m with 180° turns). Significant main effects for time (i.e. training application) and group (training type) were detected. Improvements in horizontal jumping were higher (p<0.01: ES=large) in PLYO. The RS group improved significantly more (p<0.01; ES=large) than other groups: 30 m sprint, RSAbest and RSAmean performances. Significantly greater increases in 20 m zigzag performance were observed following AG and RS training (4.0 and 3.8%, respectively) compared with PLYO (2.0%) and CON training (0.8%). No significant differences were reported in the RSAdec between groups. Elite young male soccer players' physical performances can be significantly and specifically improved either using PLYO or AG or RSA training over short-term in-season training.


#6 The influence of relative age on success and dropout in male soccer players
Reference: Am J Hum Biol. 1998;10(6):791-798. doi: 10.1002/(SICI)1520-6300(1998)10:6<791::AID-AJHB10>3.0.CO;2-1.
Authors: Helsen WF, Starkes JL, Van Winckel J
Summary: The consistent asymmetry in the birth-date distribution of senior professional soccer players has led us to investigate whether similar asymmetries emerge throughout youth categories in soccer. Birth dates were considered for professional players, national youth teams, youth players transferred to top teams, and regular youth league players. Kolmogorov Smirnov tests assessed differences between observed and expected birth-date distributions. Regression analyses examined the relationship between month of birth and number of participants at various levels of play in soccer. Results indicated that youth players born from August to October (the early part of the selection year), beginning in the 6-8 year age group, are more likely to be identified as talented and to be exposed to higher levels of coaching. Eventually, these players are more likely to be transferred to top teams, to play for national teams, and to become involved professionally. In comparison, players born late in the selection year tended to dropout as early as 12 years of age. Recommendations suggest a review of the 24-month age band and current methods for talent detection and selection.


#7 Infrared thermography applied to lower limb muscles in elite soccer players with functional ankle equinus and non-equinus condition
Reference: PeerJ. 2017 May 25;5:e3388. doi: 10.7717/peerj.3388. eCollection 2017.
Authors: Rodriguez-Sanz D, Losa-Iglesias ME, Lopez-Lopez D, Calvo-Lobo C, Palomo-Lopez P, Becerro-de-Bengoa-Vallejo R
Download link: https://peerj.com/articles/3388.pdf
Summary: Gastrocnemius-soleus equinus (GSE) is a foot-ankle complaint in which the extensibility of the gastrocnemius (G) and soleus muscles (triceps surae) and ankle are limited to a dorsiflexion beyond a neutral ankle position. The asymmetric forces of leg muscles and the associated asymmetric loading forces might promote major activation of the triceps surae, tibialis anterior, transverses abdominal and multifidus muscles. Here, we made infrared recordings of 21 sportsmen (elite professional soccer players) before activity and after 30 min of running. These recordings were used to assess temperature modifications on the gastrocnemius, tibialis anterior, and Achilles tendon in GSE and non-GSE participants. We identified significant temperature modifications among GSE and non-GSE participants for the tibialis anterior muscle (mean, minimum, and maximum temperature values). The cutaneous temperature increased as a direct consequence of muscle activity in GSE participants. IR imaging capture was reliable to muscle pattern activation for lower limb. Based on our findings, we propose that non-invasive IR evaluation is suitable for clinical evaluation of the status of these muscles.


#8 Quantitative EEG evaluation for performance level analysis of professional female soccer players
Reference: Cogn Neurodyn. 2017 Jun;11(3):233-244. doi: 10.1007/s11571-017-9427-3. Epub 2017 Feb 24.
Authors: Tharawadeepimuk K, Wongsawat Y
Summary: Quantitative electroencephalography (QEEG) was used to investigate the brain activity of Thai professional female soccer team players who exhibit high performance. The QEEGs of 29 players were recorded three times: twice before a competition (once a week) and a week after a competition. The results of the brain topographic map (absolute power) in the alpha frequency band and the brain connectivity (coherence) in the delta frequency bands represented their anxiety and decision-making levels, respectively. These phenomena occurred in the brain activities of the athletes, which could be used to predict their performances during the competition. Moreover, the value of the correlation coefficient between the brain activity ranking and average performance score revealed a moderate to good relationship (rs = .586, p = .001). These results support the association between brain activity and performance level during competition.


#9 Decrements in neuromuscular performance and increases in creatine kinase impact training outputs in elite soccer players
Reference: J Strength Cond Res. 2017 May 23. doi: 10.1519/JSC.0000000000001997. [Epub ahead of print]
Authors: Malone S, Mendes B, Hughes B, Roe M, Devenney S, Collins K, Owen A.
Summary: The aim of the current investigation was to understand the impact of pre-training neuromuscular performance and creatine kinase status on subsequent training performance in elite soccer players. Thirty soccer players (age: 25.3 ± 3.1 years; height: 183 ± 7 cm; mass: 72 ± 7 kg) were involved in this observational study. Each morning prior to training, players completed assessments for neuromuscular performance (countermovement jump; CMJ) and creatine kinase (CK) levels. Global positioning technology provided external load: total distance, high-speed distance, sprint distance, accelerations, decelerations, average metabolic power, explosive distance, high metabolic power distance (>25.5 W·kg). Mixed-effect linear models revealed significant effects for CK and CMJ Z-score on total high speed distance, very high speed distance, accelerations, decelerations, explosive distance and maximal velocity. Effects are reported with 90% confidence limits. A CK Z-score of +1 corresponded to a -5.5 ± 1.1, -3.9 ± 0.5, -4.3 ± 2.9%, 4.1 ± 2.9%, 3.1 ± 2.9% and -4.6 ± 1.9%, reduction in total high-speed distance, very high-speed distance, accelerations, decelerations, explosive distance and maximal velocity respectively. CMJ Z-score of -1 corresponded to a -3.5 ± 1.1, -2.9 ± 0.5, -2.1 ± 1.4, -5.3 ± 2.9%, 3.8 ± 2.9%, 1.1 ± 2.9% and -5.6 ± 1.2% reduction in these external load measures. Magnitude-based analysis revealed that the practical size of the effect of a pre-training CMJ Z-score of -1 and CK Z-score of +1 would have on total high speed distance, very high speed distance, high metabolic power distance (>25.5 W·kg), accelerations, decelerations, explosive distance and maximal velocity was likely negative. The results of this study suggest that systematic pre-training monitoring of neuromuscular and muscle stress within soccer cohorts can provide coaches with information about the training output that can be expected from individual players during a training session.


#10 The effects of game types on intensity of small-sided games among pre-adolescent youth football players
Reference: Biol Sport. 2017 Jun;34(2):157-162. doi: 10.5114/biolsport.2017.64589. Epub 2017 Jan 1.
Authors: Halouani J, Chtourou H, Dellal A, Chaouachi A, Chamari K
Summary: The aim of this study was to examine the effects of variations in pitch dimensions on pre-adolescent youth soccer players' physiological responses during two different types of small-sided games (SSG). Sixteen young soccer players (age: 13.2 ± 0.6 years; body mass: 52.5 ± 7 kg; height: 163.4 ± 6 cm) participated in this study. They performed 4 vs. 4 stop-ball SSG (SB-SSG) vs. small-goals SSG (SG-SSG) with 4×4 min and 2 min of passive recovery in between, using 3 different pitch sizes (small: 10×15, medium: 15×20, and large: 20×25 m). Heart rate (HR), lactate concentration ([La-]), and rating of perceived exertion (RPE) were measured during each session. The results show that SB-SSG induced higher HR responses than SG-SSG for the 3 pitch sizes: for HR (167.2±3.0 vs. 164.5±3.0, 172.3±2.9 vs. 169.2±3.1, and 175.4±3.1 vs. 171.1±2.7 bpm; P<0.05, for small, medium, and large, respectively) and [La-] (7.1±1.0 vs. 6.5±1.04, 7.3±1.0 vs. 6.8±1.2, and 7.8±0.9 vs. 7.1±0.8 mmol·l-1; P<0.05 on small, medium, and large pitches, respectively), whereas RPE scores were significantly higher during SB-SSG compared to SG-SSG (6.2±1.0 vs. 5.8±0.9; P<0.05, respectively) on the small pitch. In the present study higher physiological responses were observed in SSG in pre-adolescent young soccer players when using the stop-ball conditions in comparison with the small-goal rule for all pitch sizes - small, medium, and large. Stop-ball conditions in comparison with the small-goal rule for all pitch sizes - small, medium, and large.



American Football
#1 Greater circadian disadvantage during evening games for the National Basketball Association (NBA), National Hockey League (NHL) and National Football League (NFL) teams travelling westward
Reference: J Sleep Res. 2017 Jun 1. doi: 10.1111/jsr.12565. [Epub ahead of print]
Authors: Roy J, Forest G
Summary: We investigated the effects of a circadian disadvantage (i.e. playing in a different time zone) on the winning percentages in three major sport leagues in North America: the National Basketball Association, the National Hockey League and the National Football League. We reviewed 5 years of regular season games in the National Basketball Association, National Hockey League and National Football League, and noted the winning percentage of the visiting team depending on the direction of travel (west, east, and same time zone) and game time (day and evening games). T-tests and analysis of variance were performed to evaluate the effects of the circadian disadvantage, its direction, the number of time zones travelled, and the game time on winning percentages in each major league. The results showed an association between the winning percentages and the number of time zones traveled for the away evening games, with a clear disadvantage for the teams travelling westward. There was a significant difference in the teams' winning percentages depending on the travelling direction in the National Basketball Association (F2,5908  = 16.12, P < 0.0001) and the National Hockey League (F2,5639  = 4.48, P = 0.011), and a trend was found in the National Football League (F2,1279  = 2.86, P = 0.058). The effect of the circadian disadvantage transcends the type of sport and needs to be addressed for greater equity among the western and eastern teams in professional sports. These results also highlight the importance of circadian rhythms in sport performance and athletic competitions.


#2 Return to Play After Shoulder Instability Surgery in National Collegiate Athletic Association Division I Intercollegiate Football Athletes
Reference: Am J Sports Med. 2017 May 1:363546517705635. doi: 10.1177/0363546517705635. [Epub ahead of print]
Authors: Robins RJ, Daruwalla JH, Gamradt SC, McCarty EC, Dragoo JL, Hancock RE, Guy JA, Cotsonis GA, Xerogeanes JW; ASP Collaborative Group, Greis PE, Tuman JM, Tibone JE, Javernick MA, Yochem EM, Boden SA, Pilato A, Miley JH
Summary: Recent attention has focused on the optimal surgical treatment for recurrent shoulder instability in young athletes. Collision athletes are at a higher risk for recurrent instability after surgery. The purpose was to evaluate variables affecting return-to-play (RTP) rates in Division I intercollegiate football athletes after shoulder instability surgery. Invitations to participate were made to select sports medicine programs that care for athletes in Division I football conferences (Pac-12 Conference, Southeastern Conference [SEC], Atlantic Coast Conference [ACC]). After gaining institutional review board approval, 7 programs qualified and participated. Data on direction of instability, type of surgery, time to resume participation, and quality and level of play before and after surgery were collected. There were 168 of 177 procedures that were arthroscopic surgery, with a mean 3.3-year follow-up. Overall, 85.4% of players who underwent arthroscopic surgery without concomitant procedures returned to play. Moreover, 15.6% of athletes who returned to play sustained subsequent shoulder injuries, and 10.3% sustained recurrent instability, resulting in reduction/revision surgery. No differences were noted in RTP rates in athletes who underwent anterior labral repair (82.4%), posterior labral repair (92.9%), combined anterior-posterior repair (84.8%; P = .2945), or open repair (88.9%; P = .9362). Also, 93.3% of starters, 95.4% of utilized players, and 75.7% of rarely used players returned to play. The percentage of games played before the injury was 49.9% and rose to 71.5% after surgery ( P < .0001). Athletes who played in a higher percentage of games before the injury were more likely to return to play; 91% of athletes who were starters before the injury returned as starters after surgery. Scholarship status significantly correlated with RTP after surgery ( P = .0003). The majority of surgical interventions were isolated arthroscopic stabilization procedures, with no statistically significant difference in RTP rates when concomitant arthroscopic procedures or open stabilization procedures were performed. Athletes who returned to play often played in a higher percentage of games after surgery than before the injury, and many played at the same or a higher level after surgery.

Fri

16

Jun

2017

World Conference on Science and Soccer - Presentations Day 3 Part I

Day 3 of the World Conference on Science and Soccer started with some Talent Identification. Below are some slides from the first session.

Paul Larkin

Maxime Hertzog