Latest research in football - week 14 - 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 Injuries in male and female semi-professional football (soccer) players in Nigeria: prospective study of a National Tournament
Reference: BMC Res Notes. 2017 Mar 21;10(1):133. doi: 10.1186/s13104-017-2451-x.
Authors: Owoeye OB, Aiyegbusi AI, Fapojuwo OA, Badru OA, Babalola AR
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Summary: Research on the epidemiology of football injuries in Africa is very sparse despite its importance for injury prevention planning in a continent with limited sports medicine resources. The vast majority of studies available in literature were conducted in Europe and only a very few studies have prospectively reported the pattern of football injury in Africa. The purpose of this study was to evaluate the incidence and pattern of injuries in a cohort of male and female semi-professional football players in Nigeria. A prospective cohort design was conducted, in which a total of 756 players with an age range of 18-32 years (356 males and 300 females) from 22 different teams (12 male and 10 female teams), were prospectively followed in a National Football Tournament. Physiotherapists recorded team exposure and injuries. Injuries were documented using the consensus protocol for data collection in studies relating to football injury surveillance. An overall incidence of 113.4 injuries/1000 h (95% CI 93.7-136.0) equivalent to 3.7 injuries/match and time-loss incidence of 15.6 injuries/1000 h were recorded for male players and 65.9 injuries/1000 h (95% CI 48.9-86.8) equivalent to 2.2 injuries/match and time-loss incidence of 7.9 injuries/1000 h were recorded for female players. Male players had a significantly higher risk of injuries [IRR = 1.72 (95% CI 1.23-2.45)]. Injuries mostly affected the lower extremity for both genders (n = 81, 70% and n = 31, 62% for males and females respectively). Lower leg contusion (n = 22, 19%) and knee sprain (n = 9, 18%) were the most common specific injury types for male and female players respectively. Most of the injuries were as a result of contact with another player (n = 102, 88%-males; n = 48, 96%-females). Time-loss injuries were mostly estimated as minimal (n = 11, 69%) for male players and severe (n = 4, 66%) for female players. The overall incidence of injuries among Nigerian semi-professional football players is high but most of the injuries do not result in time-loss. Pattern of injuries is mostly consistent with previous studies. More prospective studies are needed to establish injury prevention initiatives among African players.

#2 Geographical Variations in the Interaction of Relative Age Effects in Youth and Adult Elite Soccer
Reference: Front Psychol. 2017 Mar 7;8:278. doi: 10.3389/fpsyg.2017.00278. eCollection 2017.
Authors: Steingrover C, Wattie N, Baker J, Helsen WF, Schorer J
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Summary: Selection biases based on the use of cut-off dates and the timing of athletes' birthdates have been termed relative age effects. These effects have been shown to differentially affect individuals involved in sport. For example, young male soccer players born early in their age group are overrepresented in elite teams while studies in adult soccer indicated potential carry-over effects from talent development systems. This two-study approach focuses on the processes within multi-year age groups in youth and adult elite soccer and on the role of players' age position within the age band with regard to players' birth year and birth month. Study 1 tests for an interaction of two different types of relative age effects among data from participants in the last five Under-17 FIFA World Cups (2007-2015). Analyses revealed a significant global within-year effect and varying birthdate distributions were found between confederations. Even stronger effects were found for constituent year effects. For the total sample, a multi-way frequency analysis (MFA) revealed an interaction with a pattern of a stronger within-year effect for the younger year group. This study highlights the need to consider interactions between different types of age effects. The main aim of Study 2 was to test for carry-over effects from previously found constituent year effects among players participating in the 2014 soccer World Cup and, therefore, to test for long-term effects of age grouping structures used during earlier stages of talent development. A secondary purpose of this study was to replicate findings on the existence of within-year effects and to test whether effects vary between continental confederations. No significant interaction between constituent year and within-year effects was shown by the MFA among the World Cup sample and previous findings on varying within-year effects were replicated. Results indicate that long-term effects of age grouping structures in earlier high-level talent development structures exist.

#3 The effects of an increased calorie breakfast consumed prior to simulated match-play in Academy soccer players
Reference: Eur J Sport Sci. 2017 Mar 21:1-9. doi: 10.1080/17461391.2017.1301560. [Epub ahead of print]
Authors: Briggs MA, Harper LD, McNamee G, Cockburn E, Rumbold PL, Stevenson EJ, Russell M
Summary: Dietary analysis of Academy soccer players highlights that total energy and carbohydrate intakes are less than optimal, especially, on match-days. As UK Academy matches predominantly kick-off at ∼11:00 h, breakfast is likely the last pre-exercise meal and thus may provide an intervention opportunity on match-day. Accordingly, the physiological and performance effects of an increased calorie breakfast consumed ∼135-min before soccer-specific exercise was investigated. English Premier League Academy soccer players (n = 7) repeated a 90-min soccer match simulation on two occasions after consumption of habitual (Bhab; ∼1100 kJ) or increased (Binc; ∼2100 kJ) energy breakfasts standardised for macronutrient contributions (∼60% carbohydrates, ∼15% proteins and ∼25% fats). Countermovement jump height, sprint velocities (15-m and 30-m), 30-m repeated sprint maintenance, gut fullness, abdominal discomfort and soccer dribbling performances were measured. Blood samples were taken at rest, pre-exercise, half-time and every 15-min during exercise. Although dribbling precision (P = .522; 29.9 ± 5.5 cm) and success (P = .505; 94 ± 8%) were unchanged throughout all time-points, mean dribbling speed was faster (4.3 ± 5.7%) in Binc relative to Bhab (P = .023; 2.84 vs 2.75 m s-1). Greater feelings of gut fullness (67 ± 17%, P = .001) were observed in Binc without changes in abdominal discomfort (P = .595). All other physical performance measures and blood lactate and glucose concentrations were comparable between trials (all P > .05). Findings demonstrate that Academy soccer players were able to increase pre-match energy intake without experiencing abdominal discomfort; thus, likely contributing to the amelioration of energy deficits on match-days. Furthermore, whilst Binc produced limited benefits to physical performance, increased dribbling speed was identified, which may be of benefit to match-play.

#4 Effects of Plyometric Training on Physical Fitness in Prepuberal Soccer Athletes
Reference: Int J Sports Med. 2017 Mar 17. doi: 10.1055/s-0042-122337. [Epub ahead of print]
Authors: Negra Y, Chaabene H, Sammoud S, Bouguezzi R, Abbes MA, Hachana Y, Granacher U
Summary: This study aimed at examining the effects of plyometric training on stable (SPT) vs. unstable (UPT) surfaces on physical fitness in prepuberal soccer players. Male athletes were randomly assigned to SPT (n=18; age=12.7±0.2 years) or UPT (n=16; age=12.2±0.5 years). Both groups conducted 3 regular soccer training sessions per week combined with either 2 SPT or UPT sessions. Assessment of jumping ability (countermovement jump [CMJ], and standing long jump [SLJ]), speed (10-m, 20-m, 30-m sprint), agility (Illinois agility test [IAT]), and balance (stable [SSBT], unstable [USBT] stork balance test; stable [SYBT], unstable [UYBT] Y balance test) was conducted pre-and post-training. An ANCOVA model was used to test for between-group differences (SPT vs. UPT) at post-test using baseline values as covariates. No significant differences were found for CMJ height (p>0.05, d=0.54), SLJ (p>0.05; d=0.81), 10-m, 20-m, and 30-m sprint performances (p>0.05, d=0.00-0.24), IAT (p>0.05, d=0.48), and dynamic balance (SYBT and UYBT, both p>0.05, d=0.39, 0.08, respectively). Statistically significant between-group differences were detected for the USBT (p<0.01, d=1.86) and the SSBT (p<0.01, d=1.75) in favor of UPT. Following 8 weeks of SPT or UPT in prepuberal athletes, similar performance levels were observed in both groups for measures of jumping ability, speed, dynamic balance, and agility. However, if the goal is to additionally enhance static balance, UPT has an advantage over SPT.

#5 Interrelationships among Jumping Power, Sprinting Power and Pubertal Status after Controlling for Size in Young Male Soccer Players
Reference: Percept Mot Skills. 2017 Apr;124(2):329-350. doi: 10.1177/0031512516686720. Epub 2017 Jan 16.
Authors: Cunha GS, Cumming SP, Valente-Dos-Santos J, Duarte JP, Silva G, Dourado AC, Leites GT, Gaya AC, Reischak-Oliveira A, Coelho-E-Silva M
Summary: This study examined power output on jumping and sprinting tests in young soccer players of differing pubertal status, while controlling for body size with allometric scaling exponents. A total of 46 males aged 12-18 years (14.17 years) were divided into three groups: pre-pubescent ( n = 12), pubescent ( n = 22), and post-pubescent ( n = 12). Participants performed a series of tests, including the squat jump (SJ), countermovement jump (CMJ), and 10-meter and 30-meter sprint test protocols. The Post-PUB group was older ( F = 112.411, p < 0.001), more experienced in competitive soccer ( F = 8.055, p = 0.001), taller ( F = 28.940, p < 0.001), and heavier ( F = 20.618, p < 0.001), when compared to peers in the other groups. Mean differences in jumping and sprinting performances suggested a significant effect for pubertal status on performance in the 10-meter sprint (large effect size, F = 8.191, p < 0.001) and 30-meter sprint (large effect size, F = 8.093, p < 0.001) after allometric scaling. Power output derived from SJ (small effect size, F = 0.536, p = 0.001) and CMJ (small effect size, F = 1.058, p = 0.356) showed no significant differences across players of varying pubertal status. Biological maturation showed a large effect on maximal power output for sprints, but not for jumps, when the effect of body size was adjusted by statistically derived allometric exponents in young male soccer players.

#6 Redox status alterations during the competitive season in élite soccer players: focus on peripheral leukocyte-derived ROS
Reference: Intern Emerg Med. 2017 Mar 30. doi: 10.1007/s11739-017-1653-5. [Epub ahead of print]
Authors: Becatti M, Mannucci A, Barygina V, Mascherini G, Emmi G, Silvestri E, Wright D, Taddei N, Galanti G, Fiorillo C
Summary: It is well known that exercise training can deeply affect redox homeostasis by enhancing antioxidant defenses. However, exhaustive exercise can induce excessive reactive oxygen species (ROS) production, leading to oxidative stress-related tissue injury and impaired muscle contractility. Hence, ROS represent important signaling molecules whose level has to be maintained to preserve normal cellular function, but which can also accumulate in response to repetitive muscle contraction. In fact, low levels of oxidants have been suggested to be essential for muscle contraction. Both aerobic and anaerobic exercise induce ROS production from several sources (mitochondria, NADPH oxidases and xanthine oxidases); however, the exact mechanisms underlying exercise-induced oxidative stress remain undefined. Professional athletes show a high risk for oxidative stress, and consequently muscle injury or decreased performance. Based on this background, we investigated leukocyte redox homeostasis alterations during the soccer season in élite soccer players. Overall blood redox status was investigated in twenty-seven male soccer players from primary division (Italian "Serie A" team) at four critical time points during the soccer season: T0: just before the first team training session; T1: at the beginning of the season; T2: in the middle of the season and T3: at the end of the season. The main markers of muscular damage (CK, myoglobin, LDH), assessed by standard routine methods, are significantly altered at the considered time points (T0 vs T1 P < 0.01). In peripheral leukocyte subpopulations, ROS production shows significant alterations at the considered time points during the soccer season, and strictly and significantly correlates with CK values at every considered time point. Our experimental data indicate that deep redox homeostasis alterations are evident during the soccer season in élite soccer players, and that oxidative stress can be easily monitored, besides using the standard plasma biochemical parameters, by leukocyte ROS production analysis.

#7 Return to play after hamstring injuries in football (soccer): a worldwide Delphi procedure regarding definition, medical criteria and decision-making
Reference: Br J Sports Med. 2017 Mar 30. pii: bjsports-2016-097206. doi: 10.1136/bjsports-2016-097206. [Epub ahead of print]
Authors: van der Horst N, Backx F, Goedhart EA, Huisstede BM; HIPS-Delphi Group
Summary: There are three major questions about return to play (RTP) after hamstring injuries: How should RTP be defined? Which medical criteria should support the RTP decision? And who should make the RTP decision? The study aimed to provide a clear RTP definition and medical criteria for RTP and to clarify RTP consultation and responsibilities after hamstring injury. The study used the Delphi procedure. The results of a systematic review were used as a starting point for the Delphi procedure. Fifty-eight experts in the field of hamstring injury management selected by 28 FIFA Medical Centres of Excellence worldwide participated. Each Delphi round consisted of a questionnaire, an analysis and an anonymised feedback report. After four Delphi rounds, with more than 83% response for each round, consensus was achieved that RTP should be defined as 'the moment a player has received criteria-based medical clearance and is mentally ready for full availability for match selection and/or full training'. The experts reached consensus on the following criteria to support the RTP decision: medical staff clearance, absence of pain on palpation, absence of pain during strength and flexibility testing, absence of pain during/after functional testing, similar hamstring flexibility, performance on field testing, and psychological readiness. It was also agreed that RTP decisions should be based on shared decision-making, primarily via consultation with the athlete, sports physician, physiotherapist, fitness trainer and team coach. The consensus regarding aspects of RTP should provide clarity and facilitate the assessment of when RTP is appropriate after hamstring injury, so as to avoid or reduce the risk of injury recurrence because of a premature RTP.

#8 Repeated sprint ability is not enhanced by caffeine, arginine, and branched-chain amino acids in moderately trained soccer players
Reference: J Exerc Rehabil. 2017 Feb 28;13(1):55-61. doi: 10.12965/jer.1732722.361. eCollection 2017.
Authors: Ermolao A, Zanotto T, Carraro N, Fornasier T, Zaccaria M, Neunhaeuserer D, Bergamin M
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Summary: The aim was to investigate the effect of a dietary supplementation on the repeated sprint ability (RSA) performance in recreationally trained team sports athletes. Twelve young men underwent a RSA exercise protocol in five trials, in which participants ingested carbohydrates (CHO) plus caffeine (Caf), CHO plus arginine (Arg), CHO plus branched-chain amino acids (BCAA), CHO plus Caf, Arg, and BCAA (ALL), and CHO only. Heart rate, oxygen saturation, hematic lactate, ratings of perceived exertion, average sprint time, total time, best sprint time, peak power, and average power were taken. Data revealed no significant effects neither on physiological nor performance parameters with any of the supplements.

#9 Within Session Sequence of Balance and Plyometric Exercises Does Not Affect Training Adaptations with Youth Soccer Athletes
Reference: J Sports Sci Med. 2017 Mar 1;16(1):125-136. eCollection 2017.
Authors: Chaouachi M, Granacher U, Makhlouf I, Hammami R, Behm DG, Chaouachi A
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Summary: The integration of balance and plyometric training has been shown to provide significant improvements in sprint, jump, agility, and other performance measures in young athletes. It is not known if a specific within session balance and plyometric exercise sequence provides more effective training adaptations. The objective of the present study was to investigate the effects of using a sequence of alternating pairs of exercises versus a block (series) of all balance exercises followed by a block of plyometric exercises on components of physical fitness such as muscle strength, power, speed, agility, and balance. Twenty-six male adolescent soccer players (13.9 ± 0.3 years) participated in an 8-week training program that either alternated individual balance (e.g., exercises on unstable surfaces) and plyometric (e.g., jumps, hops, rebounds) exercises or performed a block of balance exercises prior to a block of plyometric exercises within each training session. Pre- and post-training measures included proxies of strength, power, agility, sprint, and balance such as countermovement jumps, isometric back and knee extension strength, standing long jump, 10 and 30-m sprints, agility, standing stork, and Y-balance tests. Both groups exhibited significant, generally large magnitude (effect sizes) training improvements for all measures with mean performance increases of approximately >30%. There were no significant differences between the training groups over time. The results demonstrate the effectiveness of combining balance and plyometric exercises within a training session on components of physical fitness with young adolescents. The improved performance outcomes were not significantly influenced by the within session exercise sequence.

#10 Comparison of Skillful vs. Less Skilled Young Soccer Players on Anthropometric, Maturation, Physical Fitness and Time of Practice
Reference: Int J Sports Med. 2017 Mar 24. doi: 10.1055/s-0042-122815. [Epub ahead of print]
Authors: Gouvea MA, Cyrino ES, Valente-Dos-Santos J, Ribeiro AS, Silva DR, Ohara D, Coelho-E-Silva MJ, Ronque ER
Summary: This study compared maturation, body composition and physical fitness between youth soccer athletes with different technical skills levels. Sixty-two young athletes (11-17 years) were categorized dichotomously in more skilled (n=31) and less skilled (n=31) groups based on 3 specific technical tests (Dribbling Speed Test [DST], Shuttle Dribble Test [SDT] and Slalom Dribble Test [SLDT]). Chronological and skeletal age, time of practice, body composition and 4 physical fitness tests were performed for comparisons. As expected, the 3 technical tests were correlated (r=0.47-0.54, P<0.05). More skilled subjects in DST and SDT showed (respectively) higher time of practice (effect size [ES]=0.72 and 0.90), and greater performance sit-ups (ES=1.23 and 0.81), squat jump (ES=1.10 and 1.08), countermovement jump (ES=1.11 and 1.10), and Yo-Yo test (ES=1.17 and 1.40) compared to the less skilled subjects (P<0.05). However, more skilled subjects in SLDT showed greater performance (P<0.05) only in the squat jump (ES=0.67) and Yo-Yo tests (ES=0.83). The results suggest that technical performance is associated with greater time of practice and some physical capabilities. Moreover, the DST and SDT tests seem to be good options to discriminate technical performance in youth soccer athletes.


#11 Preferred Hip Strategy During Landing Reduces Knee Abduction Moment In Collegiate Female Soccer Players
Reference: J Sport Rehabil. 2017 Mar 24:1-19. doi: 10.1123/jsr.2016-0026. [Epub ahead of print]
Authors: Nguyen AD, Taylor JB, Wimbish TG, Keith JL, Ford KR
Summary: Hip focused interventions are aimed to decrease frontal plane knee loading related to anterior cruciate ligament (ACL) injuries. Whether a preferred hip landing strategy decreases frontal plane knee loading is unknown. The objective was to determine if a preferred hip landing strategy during a drop vertical jump (DVJ) is utilized during a single leg landing (SLL) task and whether differences in frontal plane knee loading are consistent between a DVJ and a SLL task. Participants were dichotomized into a hip (HIP, n=9) or knee/ankle (KA, n=14) strategy group based on the percentage distribution of each lower extremity joint relative to the summated moment (% distribution) during the DVJ. Separate one-way ANOVAs examined the differences in joint specific % distribution and external knee abduction moment between the HIP and KA groups. The HIP group had significantly greater % distribution of hip moment and less % distribution of knee moment compared to the KA group during the DVJ and SLL. External knee abduction moment was also significantly less in the HIP group compared to the KA group during the DVJ. Female soccer athletes who land with a preferred hip strategy during a DVJ also land with a preferred hip strategy during a SLL. The preferred hip strategy also resulted in less external knee abduction moments during the DVJ.

#12 Effects of Bout Duration on Players' Internal and External Loads During Small-Sided Games in Young Soccer Players
Reference: Int J Sports Physiol Perform. 2017 Mar 24:1-23. doi: 10.1123/ijspp.2016-0584. [Epub ahead of print]
Authors: Koklu Y, Alemdaroglu U, Cihan H, Wong DP
Summary: This study investigated the effects of different bout durations on internal and external loads of young soccer players during different small-sided games (SSGs). Fifteen male young soccer players (average age 17 ± 1 years) participated in 2 vs 2, 3 vs 3 and 4 vs 4 SSGs. All games lasted 12 min playing time in total, but each SSG format further consisted of four bout durations: continuous (CON: 1 bout x 12 min) or interval with short (SBD: 6 bouts x 2 min), medium (MBD: 3 bouts x 4 min) or long (LBD: 2 bouts x 6 min) bout durations. During the SSGs, heart rate (HR) responses, and distance covered in different speed zones - walking, low-intensity, moderate-intensity and high-intensity running were measured. Rating of Perceived Exertion (RPE) and blood lactate (La-) were determined at the end of each SSG. The SBD format elicited significantly lower %HRmax responses compared to LBD and CON in all formats (p<0.05). The SBD format also showed significantly shorter distances covered in walking and greater distances covered in moderate-intensity running as well as significantly greater total distance covered compared to LBD and CON in all formats (p<0.05). In addition, LBD produced significantly lower La- and RPE responses than SBD and CON in all formats (p<0.05). These results suggest that coaches and sports scientists who want to achieve higher internal loads could use SBD and CON timing protocols, while those who want to achieve higher external loads might prefer to use SBD and MBD when planning to all SSG formats.


American Football

#1 The effect of repetitive subconcussive collisions on brain integrity in collegiate football players over a single football season: A multi-modal neuroimaging study
Reference: Neuroimage Clin. 2017 Mar 21;14:708-718. doi: 10.1016/j.nicl.2017.03.006. eCollection 2017
Authors: Slobounov SM, Walter A, Breiter HC, Zhu DC, Bai X, Bream T, Seidenberg P, Mao X, Johnson B, Talavage TM
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Summary: The cumulative effect of repetitive subconcussive collisions on the structural and functional integrity of the brain remains largely unknown. Athletes in collision sports, like football, experience a large number of impacts across a single season of play. The majority of these impacts, however, are generally overlooked, and their long-term consequences remain poorly understood. This study sought to examine the effects of repetitive collisions across a single competitive season in NCAA Football Bowl Subdivision athletes using advanced neuroimaging approaches. Players were evaluated before and after the season using multiple MRI sequences, including T1-weighted imaging, diffusion tensor imaging (DTI), arterial spin labeling (ASL), resting-state functional MRI (rs-fMRI), and susceptibility weighted imaging (SWI). While no significant differences were found between pre- and post-season for DTI metrics or cortical volumes, seed-based analysis of rs-fMRI revealed significant (p < 0.05) changes in functional connections to right isthmus of the cingulate cortex (ICC), left ICC, and left hippocampus. ASL data revealed significant (p < 0.05) increases in global cerebral blood flow (CBF), with a specific regional increase in right postcentral gyrus. SWI data revealed that 44% of the players exhibited outlier rates (p < 0.05) of regional decreases in SWI signal. Of key interest, athletes in whom changes in rs-fMRI, CBF and SWI were observed were more likely to have experienced high G impacts on a daily basis. These findings are indicative of potential pathophysiological changes in brain integrity arising from only a single season of participation in the NCAA Football Bowl Subdivision, even in the absence of clinical symptoms or a diagnosis of concussion. Whether these changes reflect compensatory adaptation to cumulative head impacts or more lasting alteration of brain integrity remains to be further explored.

#2 Changes in Creatine Kinase and Hormones over the Course of an American Football Season
Reference: J Strength Cond Res. 2017 Apr 4. doi: 10.1519/JSC.0000000000001920. [Epub ahead of print]
Authors: Stone JD, Kreutzer A, Mata JD, Nystrom MG, Jagim AR, Jones MT, Oliver JM.
Summary: The purpose of this study was to examine changes in creatine kinase and hormones over the course of an entire season of American football. A secondary purpose was to determine differences between starters and non-starters. Fasting blood samples were obtained from nineteen National Collegiate Athletic Association Division I (n = 19; 20 ± 1 years) football athletes over the course of a season beginning prior to the start of summer off-season conditioning (T1), before (T2) and after pre-season (T3) football camp, with remaining samples taken throughout the competitive season (T4-T8). A magnitude-based inference approach was used to define outcomes. Testosterone was higher in starters prior to the start of the season (T1, Effect Size [ES] = 0.8) and during pre-conference (T4; ES = 0.7). Post-Camp (T3) testosterone was lower in all players, though greater in starters (starters, 0.0%/0.3%/99.7%; non-starters, 0.2%/2.9%/96.9%). An increase cortisol relative to baseline (T1) was observed in starters early in season (T4, ES = 0.7; T5, ES = 0.5). Creatine kinase was elevated at all time-points in all athletes, with starters having higher circulating levels throughout season. These data demonstrate that changes in hormonal markers may be experienced over a season of football and differ by playing status. Differences between starters and non-starters may be indicative of greater damage and stress experienced by starters, which may result from a greater number of repetitions.

#3 Influence of Glenoid Defect Size and Bone Fragment Size on the Clinical Outcome After Arthroscopic Bankart Repair in Male Collision/Contact Athletes
Reference: Am J Sports Med. 2017 Apr 1:363546517700864. doi: 10.1177/0363546517700864. [Epub ahead of print]
Authors: Nakagawa S, Mae T, Yoneda K, Kinugasa K, Nakamura H
Summary: The usefulness of arthroscopic Bankart repair for collision/contact athletes has varied in previous reports. The purpose of the study was to investigate the influence of glenoid rim morphologic characteristics on the clinical outcome after arthroscopic Bankart repair without additional reinforcement procedures in male collision/contact athletes, including athletes with a large glenoid defect. Eighty-six athletes (93 shoulders) followed for a minimum of 2 years were retrospectively investigated. The sports were rugby (36 shoulders), American football (29 shoulders), and other collision/contact sports (28 shoulders). Preoperative glenoid defect size, bone fragment size, and bone union after bony Bankart repair were investigated regarding factors influencing postoperative recurrence. Postoperative changes in glenoid defect size and bone fragment size were investigated as well as their influence on the clinical outcome. Postoperative recurrence of instability was noted in 22 shoulders (23.7%). The recurrence rate was 33.3% in rugby, 17.2% in American football, and 17.9% in other collision/contact sports. The recurrence rate was only 7.1% in 28 shoulders without a preoperative glenoid defect, but it increased to 43.8% in 16 shoulders that did not have a bone fragment even though there was a preoperative glenoid defect. Additionally, the recurrence rate was 7.7% in 26 shoulders with bone union after arthroscopic bony Bankart repair but rose to 45% in 20 shoulders without bone union. In the shoulders with bone union, the mean bone fragment size increased from 8.2% preoperatively to 15.2% postoperatively, while the mean glenoid defect size decreased from 18.0% to 2.8%, respectively. The recurrence rate was 8.3% in shoulders with a final glenoid defect 5% or less versus 38.1% in shoulders with a defect greater than 5%. While the recurrence rate was low among athletes other than rugby players with a final defect of 10% or less, it was low in only the rugby players with a defect of 0%. In male collision/contact athletes, while the overall clinical outcome was unsatisfactory, a favorable outcome was achieved in athletes without a preoperative glenoid defect and athletes with bone union. The glenoid defect decreased in size postoperatively due to remodeling of the united bone fragment, and the recurrence rate was low when the final glenoid defect size was 5% or less.

#4 Epidemiology of Knee Sprains in Youth, High School, and Collegiate American Football Players
Reference: J Athl Train. 2017 Apr 17. doi: 10.4085/1062-6050-52.3.09. [Epub ahead of print]
Authors: Clifton DR, Onate JA, Schussler E, Djoko A, Dompier TP, Kerr ZY
Summary: Variations in knee-sprain incidence among competition levels are unclear but may help inform prevention strategies in American football players. The purpose of the study was to describe the epidemiology of knee sprains in youth, high school, and collegiate football players. Injury and athlete-exposure (AE) data were collected from 3 injury-surveillance programs at the youth, high school, and collegiate competition levels. Data from 310 youth, 184 high school, and 71 collegiate football team-seasons were collected during the 2012 through 2014 seasons. Knee-sprain rates and risks were calculated for each competition level. Injury rate ratios (IRRs) and risk ratios (RRs) compared knee-sprain rates by competition level. Injury proportion ratios (IPRs) compared differences in surgery needs, recurrence, injury mechanism, and injury activity by competition level. Knee-sprain rates in youth, high school, and collegiate football were 0.16/1000 AEs, 0.25/1000 AEs, and 0.69/1000 AEs, respectively. Knee-sprain rates increased as the competition level increased (high school versus youth: IRR = 1.60; 95% confidence interval [CI] = 1.12, 2.30; collegiate versus high school: IRR = 2.73; 95% CI = 2.38, 3.96). Knee-sprain risk was highest in collegiate (4.3%), followed by high school (2.0%) and youth (0.5%) athletes. Knee-sprain risk increased as the competition level increased (high school versus youth: RR = 3.73; 95% CI = 2.60, 5.34; collegiate versus high school: RR = 2.14; 95% CI = 1.83, 2.51). Collegiate football had the lowest proportion of knee sprains that were noncontact injuries (collegiate versus youth: IPR = 0.54; 95% CI = 0.31, 0.95; collegiate versus high school: IPR = 0.59; 95% CI = 0.44, 0.79) and the lowest proportion that occurred while being tackled (collegiate versus youth: IPR = 0.44; 95% CI = 0.26, 0.76; collegiate versus high school: IPR = 0.71; 95% CI = 0.51, 0.98). Knee-sprain incidence was highest in collegiate football. However, level-specific variations in the distributions of knee sprains by injury activity may highlight the need to develop level-specific policies and prevention strategies that ensure safe sports play.

#5 Long-Term Cognitive and Neuropsychiatric Consequences of Repetitive Concussion and Head-Impact Exposure
Reference: J Athl Train. 2017 Mar;52(3):309-317. doi: 10.4085/1062-6050-52.1.14.
Authors: McAllister T, McCrea M
Summary: Initially, interest in sport-related concussion arose from the premise that the study of athletes engaged in sports associated with high rates of concussion could provide insight into the mechanisms, phenomenology, and recovery from mild traumatic brain injury. Over the last decade, concerns have focused on the possibility that, for some athletes, repetitive concussions may raise the long-term risk for cognitive decline, neurobehavioral changes, and neurodegenerative disease. First conceptualized as a discrete event with variable recovery trajectories, concussion is now viewed by some as a trigger of neurobiological events that may influence neurobehavioral function over the course of the life span. Furthermore, advances in technology now permit us to gain a detailed understanding of the frequency and intensity of repetitive head impacts associated with contact sports (eg, football, ice hockey). Helmet-based sensors can be used to characterize the kinematic features of concussive impacts, as well as the profiles of typical head-impact exposures experienced by athletes in routine sport participation. Many large-magnitude impacts are not associated with diagnosed concussions, whereas many diagnosed concussions are associated with more modest impacts. Therefore, a full understanding of this topic requires attention to not only the effects of repetitive concussions but also overall exposure to repetitive head impacts. This article is a review of the current state of the science on the long-term neurocognitive and neurobehavioral effects of repetitive concussion and head-impact exposure in contact sports.


Australian football

#1 Competition Sleep Is Not Compromised Compared To Habitual In Elite Australian Footballers
Reference: Int J Sports Physiol Perform. 2017 Apr 19:1-23. doi: 10.1123/ijspp.2016-0776. [Epub ahead of print]
Authors: Lalor BJ, Halson SL, Tran J, Kemp JG, Cormack SJ
Summary: The purpose was to assess the impact of match start time and days relative to match compared to the habitual sleep characteristics of elite Australian Football (AF) players. 45 elite male AF players were assessed during the pre-season (habitual) and across four home matches during the season. Players wore an activity monitor the night before (-1), night of (0), one night after (+1), and two nights (+2) after each match and completed a self-reported rating of sleep quality. A two-way ANOVA with Tukey's post hoc was used to determine differences in sleep characteristics between match start times and days relative to the match. Two-way nested ANOVA was conducted to examine differences between competition and habitual phases. The Effect size ± 90% confidence interval (ES ± 90% CI) was calculated to quantify the magnitude of pairwise differences. Differences observed in sleep onset latency (ES=0.11 ± 0.16), sleep rating (ES=0.08 ± 0.14) and sleep duration (ES=0.08 ± 0.01) between competition and habitual periods were trivial. Sleep efficiency (%) was almost certainly higher during competition than habitual, however this was not reflected in the subjective rating of sleep quality. Elite AF competition does not cause substantial disruption to sleep characteristics compared to habitual sleep. Whilst match start time has some impact on sleep variables, it appears that the match itself is more of a disruption than the start time. Subjective ratings of sleep from well-being questionnaires appear limited in their ability to accurately provide an indication of sleep quality.

#2 The association between fundamental athletic movements and physical fitness in elite junior Australian footballers
Reference: J Sports Sci. 2017 Apr 13:1-6. doi: 10.1080/02640414.2017.1313996. [Epub ahead of print]
Authors: Woods CT, McKeown I, Keogh J, Robertson S
Summary: This study investigated the associations between fundamental athletic movement and physical fitness in junior Australian football (AF). Forty-four under 18 players performed a fundamental athletic movement assessment consisting of an overhead squat, double lunge, single leg Romanian deadlift and a push up. Movements were scored on three assessment criterions using a three-point scale. Additionally, participants performed five physical fitness tests commonly used for talent identification in AF. A Spearman's nonparametric correlation matrix was built, with correlation coefficients being visualised using a circularly rendered correlogram. Score on the overhead squat was moderately positively associated with dynamic vertical jump height on left (rs = 0.40; P ≤ 0.05) and right (rs = 0.30; P ≤ 0.05) leg take-off, stationary vertical jump (rs = 0.32; P ≤ 0.05) and negatively associated with 20-m sprint time (rs = -0.35; P ≤ 0.05). Score on the double lunge (left/right side) was moderately positively associated with the same physical fitness tests as well as score on the multistage fitness test. Results suggest that improvements in physical fitness qualities may occur through concurrent increases in fundamental athletic movement skill, namely the overhead squat and double lunge movements. These findings may assist with the identification and development of talent.

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