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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
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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
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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.





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
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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
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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
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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
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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
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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
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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
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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.





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
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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
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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
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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
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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.





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
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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
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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
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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
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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.





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
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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
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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
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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
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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.





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.





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 body mass) and post-match (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>lunch (0.6>breakfast (0.3>evening snacks (0.1 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.





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
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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
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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
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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
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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.





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.






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:
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.





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
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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.





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

Ermanno Rampininni





Latest research in football - week 21 - 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 Hamstring Injury Prevention in Soccer: Before or After Training?
Reference: Scand J Med Sci Sports. 2017 May 24. doi: 10.1111/sms.12925. [Epub ahead of print]
Authors: Lovell R, Knox M, Weston M, Siegler JC, Brennan S, Marshall PWM
Summary: We examined the effects of a 12-week program of Nordic hamstring exercises (NHE), administered before or after football training, upon eccentric hamstring strength, muscle activity, and architectural adaptations. Amateur soccer players were randomized into 3 groups. The control group (CON; n=11) undertook core stability exercises, whereas a periodized NHE program was delivered either before (NHEBEF ; n=10) or after (NHEAFT ; n=14) bi-weekly training sessions. Outcome measures included peak torque and concomitant normalized peak surface electromyography signals (sEMG) of the biceps femoris (BF) and medial hamstring (MH) muscles during knee flexor maximal eccentric contractions, performed at 30°·s-1 . Ultrasonography was used to determine BF muscle thickness, muscle fiber pennation angle, and fascicle length. Performing the NHE derived likely moderate peak torque increases in both NHEBEF (+11.9%; 90% confidence interval: 3.6% to 20.9%) and NHEAFT (+11.6%; 2.6% to 21.5%) versus CON. Maximum sEMG increases were moderately greater in the BF of both NHE training groups versus CON. There were likely moderate increases in BF muscle thickness (+0.17 cm; 0.05 cm to 0.29 cm) and likely small pennation angle increases (+1.03°; -0.08° to 2.14°) in NHEAFT versus CON and NHEBEF . BF fascicle length increases were likely greater in NHEBEF (+1.58 cm; 0.48 cm to 2.68 cm; small effect) versus CON and NHEAFT . A 12-week eccentric hamstring-strengthening program increased strength and sEMG to a similar magnitude irrespective of its scheduling relative to the football training session. However, architectural adaptations to support the strength gains differed according to the timing of the injury prevention program.

#2 Heart Rate Variability Discriminates Competitive Levels in Professional Soccer Players
Reference: J Strength Cond Res. 2017 Jun;31(6):1719-1725. doi: 10.1519/JSC.0000000000001795.
Authors: Proietti R, di Fronso S, Pereira LA, Bortoli L, Robazza C, Nakamura FY, Bertollo M.
Summary: Heart rate variability (HRV) has been increasingly used to monitor team sports athletes. Besides the traditional time domain indices (i.e., the SD of successive RR intervals [SDNN] and the root mean square difference of successive normal RR intervals [RMSSD]), recently the use of the stress score (SS), which is an inverse function of the SD2 index derived from the Poincaré plot, and the sympathetic/parasympathetic ratio (S/PS) to monitor soccer players has been proposed. However, the reliability of these new indices and the ability of HRV to differentiate between soccer competitive levels are unknown. The aim of this study was to analyze the reliability of the different HRV-derived indices in professional soccer players during the competitive period and to compare HRV of professional soccer players from 3 teams of distinct competitive levels (i.e., Italian Second Division [2D], European League [EL], and Champions League [CL]). Fifty-four male professional soccer players from 3 different teams of 2 European countries (Italy and Germany) participated in the study. The intraclass correlation coefficient values of the HRV indices varied from 0.78 (very large) to 0.90 (near perfect). The coefficient of variation (CV) values for RMSSD and SDNN were all <5.00%, although the CV for SS was 6.13% and for S/PS, it was 21.33%. Both the CL and EL groups, assumed to be internationally qualified, presented higher lnRMSSD and lnSDNN and lower lnSS and S/PS than the 2D. Therefore, the HRV can be considered reliable in professional soccer players and is able to differentiate between international- and national-level players.

#3 Maximal Sprinting Speed of Elite Soccer Players During Training and Matches
Reference: J Strength Cond Res. 2017 Jun;31(6):1509-1517. doi: 10.1519/JSC.0000000000001642.
Authors: Djaoui L, Chamari K, Owen AL, Dellal A
Summary: The aim of the present study was to compare (a) the maximal sprinting speed (MSS) attained by soccer players during matches (MSSmatch) according to their level of play (professional first French division vs. elite amateur fourth French division) and the playing positions and (b) the MSS attained by professional soccer players during 14 different types of small-sided games (SSG, MSSSSG) and match-play. All players monitored through the study performed a 40-m sprint test to assess individual MSS (MSStest) and compare it to the training and match activity, with the calculation of the percentage of MSStest (%MSStest) reached. No differences were found according to the level of play; however, positional wide players achieved a higher MSSmatch, %MSStest, and MSSSSG than central players (both defenders and midfielders) during matches and SSG. MSSmatch were higher than all MSSSSG, and MSSSSG were positively correlated with the area of the pitch (0.45, p < 0.001), its length (0.53, p < 0.001), and the number of players involved (0.38, p < 0.001). The closer SSG was to match situation in terms of rules, the higher the MSSSSG. Wide players reached higher MSS in match and SSG than central players, confirming the relevance of using SSG close to match situation to specifically prepare elite players to the maximal running speed demand of the match.

#4 Quantifying the High-Speed Running and Sprinting Profiles of Elite Female Soccer Players During Competitive Matches Using an Optical Player Tracking System
Reference: J Strength Cond Res. 2017 Jun;31(6):1500-1508. doi: 10.1519/JSC.0000000000001629.
Authors: Mara JK, Thompson KG, Pumpa KL, Morgan S.
Summary: Quantifying the high-speed running and sprinting profiles of elite female soccer players during competitive matches using an optical player tracking system. J Strength Cond Res 31(6): 1500-1508, 2017-The aim of this study was to determine the high-speed running and sprinting profiles of elite female soccer players during competitive matches using a new Optical Player Tracking system. Eight stationary video cameras were positioned at vantage points surrounding the soccer field so that when each camera view was combined, the entire field could be viewed simultaneously. After each match, an optical player tracking system detected the coordinates (x, y) of each player for every video frame. Algorithms applied to the x and y coordinates were used to determine activity variables for 12 elite female players across 7 competitive matches. Players covered 9,220-10,581 m of total distance, 1,772-2,917 m of high-speed running (3.4-5.3 m·s) distance, and 417-850 m of sprinting (>5.4 m·s) distance, with variations between positional groups (p < 0.001; partial η = 0.444-0.488). Similarly, the number of high-speed runs differed between positional groups (p = 0.002; partial η = 0.342), and a large proportion of high-speed runs (81-84%) and sprints (71-78%) were performed over distances less than 10 m. Mean time between high-speed runs (13.9 ± 4.4 seconds) and sprints (86.5 ± 38.0 seconds) varied according to playing position (p < 0.001; partial η = 0.409) and time of the match (p < 0.001; partial η = 0.113-0.310). The results of this study can be used to design match-specific conditioning drills and shows that coaches should take an individualized approach to training load monitoring according to position.

#5 Exercise Intensity and Technical Demands of Small-Sided Soccer Games for Under-12 and Under-14 Players: Effect of Area per Player
Reference: J Strength Cond Res. 2017 Jun;31(6):1486-1492. doi: 10.1519/JSC.0000000000001615.
Authors: Martone D, Giacobbe M, Capobianco A, Imperlini E, Mancini A, Capasso M, Buono P, Orru S
Summary: The aim of this study was to evaluate the effects of 6 different areas per player (AP) on exercise intensity (EI) measured during small-sided games (SSGs) and expressed as percentage of maximal heart rate (%MHR) and technical actions (TAs) involvement with the ball, crosses, headers, tackles, shots on goal, dribbling, passing, and target passing-in U-12 and U-14 soccer players during SSGs. Seventeen male U-12 soccer players (age 10.0 ± 0.5 years, body mass 39.3 ± 5.3 kg, and height 143.8 ± 4.6 cm) and 16 male U-14 soccer players (age 13.2 ± 0.3 years, body mass 46.6 ± 11.9 kg, and height 154.8 ± 8.5 cm) performed SSGs with different AP: 40, 50, 66.7, 90, 112.5, and 150 m. Our results indicate that at larger AP, the U-12 group's mean EI values were significantly higher than those at smaller AP (p ≤ 0.05); in addition, intergroup comparison showed that EI was higher in U-12 than that in U-14 players when AP of 112.5 and 150 m were considered (p ≤ 0.05). Technical action analysis evidenced that moving from smaller to larger AP, U-14 players adapted better to AP changes. In conclusion, these results suggest that AP influences differently EI and TAs in U-12 and U-14 players. Our results could be taken into account by conditioning coaches to better tailor the physiological and technical training in young players through the modulation of AP.

#6 Relationship Between Internal Load Indicators and Changes on Intermittent Performance After the Preseason in Professional Soccer Players
Reference: J Strength Cond Res. 2017 Jun;31(6):1477-1485. doi: 10.1519/JSC.0000000000001613.
Authors: Campos-Vazquez MA, Toscano-Bendala FJ, Mora-Ferrera JC, Suarez-Arrones LJ
Summary: The aim of this study was to examine the effects of accumulated internal training load (ITL) during the preseason (4 weeks) on changes in the intermittent performance, in a professional soccer team. Twelve professionals soccer players (Mean ± SD age: 27.7 ± 4.3 years; height: 177.1 ± 6.2 cm; body mass: 73.1 ± 5.2 kg; % body fat [Faulkner]: 10.2 ± 1.2) belonging to a Spanish second division team (2013-2014) participated in this study. The 30-15 intermittent fitness test was performed before and after the preseason, and the speed for the last period completed by each player was recorded (VIFT). During the preseason, the team alternated practice of training sessions (TRNs) with friendly matches (FMs). Session rating of perceived exertion (sRPE), heart rate (HR), and HR reserve were analyzed every TRN and FM to calculate ITL (ITL: sRPE-TL, Edward's-TL and Edward's-TLres). The players' VIFT substantially increased after the preseason period (20.1 ± 0.8 vs. 21.1 ± 0.8 km·h; effect size [ES] = 1.15 ± 0.25; almost certainly). The average value of sRPE throughout FMs was substantially greater than the value of the TRNs (7.4 ± 0.9 vs. 5.25 ± 0.2; ES = 2.31 ± 2.45; almost certainly). sRPE-TL, practice volume, and sum of RPE during the preseason were positively and largely correlated (r = 0.70-0.75) with changes on intermittent performance. No relationships were found between HR-derived measures of exercise load and changes on intermittent fitness. The present results suggest that practice volume and subjective measures of TL, related better than HR-based TL methods to changes on intermittent performance after the preseason, in professional soccer players.

#7 Effects of Different Combinations of Strength, Power, and Plyometric Training on the Physical Performance of Elite Young Soccer Players
Reference: J Strength Cond Res. 2017 Jun;31(6):1468-1476. doi: 10.1519/JSC.0000000000001609.
Authors: Kobal R, Loturco I, Barroso R, Gil S, Cuniyochi R, Ugrinowitsch C, Roschel H, Tricoli V
Summary: Effects of different combinations of strength, power, and plyometric training on the physical performance of elite young soccer players. J Strength Cond Res 31(6): 1468-1476, 2017-The combination of strength (ST) and plyometric training (PT) has been shown to be effective for improving sport-specific performance. However, there is no consensus about the most effective way to combine these methods in the same training session to produce greater improvements in neuromuscular performance of soccer players. Thus, the purpose of this study was to compare the effects of different combinations of ST and PT sequences on strength, jump, speed, and agility capacities of elite young soccer players. Twenty-seven soccer players (age: 18.9 ± 0.6 years) participated in an 8-week resistance training program and were divided into 3 groups: complex training (CP) (ST before PT), traditional training (TD) (PT before ST), and contrast training (CT) (ST and PT performed alternately, set by set). The experimental design took place during the competitive period of the season. The ST composed of half-squat exercises performed at 60-80% of 1 repetition maximum (1RM); the PT composed of drop jump exercises executed in a range from 30 to 45 cm. After the experimental period, the maximum dynamic strength (half-squat 1RM) and vertical jump ability (countermovement jump height) increased similarly and significantly in the CP, TD, and CT (48.6, 46.3, and 53% and 13, 14.2, and 14.7%, respectively). Importantly, whereas the TD group presented a significant decrease in sprinting speed in 10 (7%) and 20 m (6%), the other groups did not show this response. Furthermore, no significant alterations were observed in agility performance in any experimental group. In conclusion, in young soccer players, different combinations and sequences of ST and PT sets result in similar performance improvements in muscle strength and jump ability. However, it is suggested that the use of the CP and CT methods is more indicated to maintain/maximize the sprint performance of these athletes.

#8 Immediate effect of ankle balance taping on dynamic and static balance of soccer players with acute ankle sprain
Reference: J Phys Ther Sci. 2017 Apr;29(4):622-624. doi: 10.1589/jpts.29.622. Epub 2017 Apr 20.
Authors: Shin YJ, Kim MK
Download link:
Summary: This study aimed to evaluate the immediate effect of ankle balance taping on balance ability of soccer players with acute ankle sprain. This study was conducted with 16 subjects who were diagnosed with ankle sprain. A cross-over randomized design was used. Each subject performed three interventions in a random order. Subjects were randomly assigned to an ankle balance taping, placebo taping, and no taping. For dynamic and static balance, ability was measured using BIORescue (RM Ingenierie, Rodes, France). Limit of stability, sway length and sway speed for one minute were measured. The Limit of Stability, Sway length and Sway speed differed significantly among the three different taping methods. In this study, we found that ankle balance taping was effective in terms of improving balance ability of soccer players with an ankle sprain.

#9 A cross-sectional study on the relationship between nutritional knowledge and physical fitness in soccer players
Reference: Clin Nutr ESPEN. 2016 Jun;13:e70. doi: 10.1016/j.clnesp.2016.03.063. Epub 2016 May 20.
Authors: Nikolaidis PT, Theodoropoulou E

American Football
#1 Relationship between proxies for Type II fiber type and resting blood pressure in Division I American Football Athletes
Reference: Int J Health Sci (Qassim). 2017 Apr-Jun;11(2):16-20.
Authors: DiCesare CA, Adams JR, Claytor RP, Ward RM, Cox RH
Summary: The risk for cardiovascular disease is well-documented. Perhaps surprisingly, specific athletic populations, including American football players, exhibit increased risk for cardiovascular disease as presented by elevated blood pressure. There is evidence suggesting a link between muscle fiber type distribution and resting blood pressure. Acknowledging this association, it becomes important to clarify an individual's risk for developing cardiovascular disease later in adulthood. The purpose of this study was to assess football performance measures-in particular proxies for muscular power-and their effect on resting blood pressure in football athletes. A total of 80 collegiate-level football players participated in this study. Each participant's body fat %, body mass index, waist circumference, and mean arterial pressure (MAP) were measured. Participants performed one-repetition maximums of bench press, back squat, 40-yard dash, and vertical leap, and a power index (PI) defined as the product of vertical leap and mass. Linear regressions were run between body composition variables and performance measures for all players and a subset of skill players only. The PI was found to be positively, significantly correlated with MAP in all players (r = 0.269; P = 0.035) and the skill players subset (r = 0.425; P = 0.004). The results of the present study indicate an association between muscle fiber type distribution, as indicated by muscular power capacity, and resting blood pressure.

#2 Nutrition practices and knowledge among NCAA Division III football players
Reference: J Int Soc Sports Nutr. 2017 May 19;14:13. doi: 10.1186/s12970-017-0170-2. eCollection 2017.
Authors: Abbey EL, Wright CJ, Kirkpatrick CM
Download link:
Summary: Participation in collegiate American football is physically demanding and may have long-term health implications, particularly in relation to cardiovascular and neurological health. National Collegiate Athletic Association (NCAA) Division III (DIII) football players are a relatively unstudied population, particularly in terms of their dietary habits and knowledge. The aim of the present study was to descriptively evaluate the dietary intake of DIII football players including a subset of linemen and assess the nutritional knowledge and sources of information of these athletes. The study sample was 88 DIII football players including a subset of nine linemen. All participants completed a food frequency questionnaire, and a nutritional knowledge questionnaire that included a quiz and questions about their main sources of nutrition information. Heights and body masses were also recorded. The linemen submitted written 3-day diet records for assessment of their dietary intake. Of the 88 participants, >50% reported consuming starches/grains, meat and dairy daily, but <50% reported consuming fruits and vegetables daily. Protein powders were the most commonly used supplements (33% reported daily use). Compared to dietary recommendations, linemen consumed high amounts of total fat, saturated fat, dietary cholesterol, sodium, and potassium, but were low in carbohydrates, fiber, and essential fats. The mean nutrition knowledge quiz score for the 88 participants was 55.2%. Those who had taken a nutrition or health course in college scored significantly higher on the quiz than those who had not. Participants reported relying primarily on coaches, websites, and athletic trainers (ATs) for nutritional guidance; ATs were the most trusted source. DIII football players had dietary habits that may both mitigate and increase their risk of chronic diseases. These athletes have room to improve their nutrition knowledge. Their reliance on athletic team staff for nutrition guidance highlights the importance of nutrition education for both athletes and staff and the potential role of a registered dietitian nutritionist.

Australian Football
#1 Australian football players experiencing groin pain exhibit reduced subscale scores of Activities of Daily Living and Sport and Recreation on the HAGOS questionnaire: A case-control study
Reference: Phys Ther Sport. 2017 Apr 20;26:7-12. doi: 10.1016/j.ptsp.2017.04.004. [Epub ahead of print]
Authors: Drew MK, Lovell G, Palsson TS, Chiarelli PE, Osmotherly PG
Summary: The objective was to report normative responses to the HAGOS questionnaire for Australian football players and to determine whether any of the HAGOS questionnaire sub scales can differentiate players with and without groin pain. Professional (n = 66) and semi-professional (n = 9) Australian football (AF) players with current groin pain (n = 16) and controls (n = 57) without current groin pain. The HAGOS subscales were compared between players with and without groin pain using the Wilcoxon rank-sum test with effect sizes (ES) calculated. Floor and ceiling effects were examined. A post-hoc factor analysis was undertaken. Participants with current groin pain showed lower Physical Function of Daily Living (PFDL) and Physical Function in Sport and Recreation (PFSR) subscale scores (p < 0.05, ES: 0.77 and 0.90 respectively). Any groin pain (current and/or historical) lowered the Pain and Quality of Life (QOL) subscale scores (p < 0.05, ES: 0.38 and 0.72 respectively). Factor analysis showed 8 significant factors with one main factor identified representing items describing forceful activities (Eigenvalue = 18.02, Proportion = 0.49). The HAGOS can distinguish AF players with current groin pain in the PFDL and PFSR subscales but not in the other four subscales. Any current or historical groin pain lowers scores on the QOL and Pain sub scales.

#2 Optimising Pre-Season Training Loads in Australian Football
Reference: Int J Sports Physiol Perform. 2017 May 22:1-19. doi: 10.1123/ijspp.2016-0695. [Epub ahead of print]
Authors: Carey DL, Crow J, Ong KL, Blanch P, Morris ME, Dascombe BJ, Crossley KM
Summary: The purpose was to investigate whether pre-season training plans for Australian football can be computer generated using current training load guidelines to optimise injury risk reduction and performance improvement. A constrained optimisation problem was defined for daily total and sprint distance, using the pre-season schedule of an elite Australian football team as a template. Maximising total training volume and maximising Banister model projected performance were both considered as optimisation objectives. Cumulative workload and acute:chronic workload ratio constraints were placed on training programs to reflect current guidelines on relative and absolute training loads for injury risk reduction. Optimisation software was then used to generate pre-season training plans. The optimisation framework was able to generate training plans that satisfied relative and absolute workload constraints. Increasing the off-season chronic training loads enabled the optimisation algorithm to prescribe higher amounts of 'safe' training and attain higher projected performance levels. Simulations showed that using a Banister model objective led to plans that included a taper in training load prior to competition in order to minimise fatigue and maximise projected performance. In contrast, when the objective was to maximise total training volume, more frequent training were prescribed in order to accumulate as much load as possible. Feasible training plans that maximise projected performance and satisfy injury risk constraints can be automatically generated by an optimisation problem for Australian football. The optimisation methods allow for individualised training plan design and the ability to adapt to changing training objectives and different training load metrics.





World Conference on Science and Soccer - Presentations Day 2

The following slides will display some of the content of the second day of the World Conference on Science and Soccer that I have visited.


Filipe Manuel Clemente

Maickel Padilha

Alan McCall

George Nassis

Bruno Grueninger





World Conference on Science and Soccer - Presentations Day 1

As mentioned in previous post, I have attended the World Conference on Science and Soccer.

Beside presenting myself I visited a couple of session/presentations, of which I took some pictures.


Brian Dawson

Barry Drust

Aaron Coutts

Arne Jaspers

Maurizio Fanchini

Matthew Walan

Robert McCunn

At the end of the first day, the Conference Gala Dinner Reception was held at the Roazhon Park, the home (stadium) of Rennes FC.






Latest research in football - week 20 - 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 Body Size of Male Youth Soccer Players: 1978-2015
Reference: Sports Med. 2017 May 18. doi: 10.1007/s40279-017-0743-x. [Epub ahead of print]
Authors: Malina RM, Figueiredo AJ, Coelho-E-Silva MJ
Summary: Studies of the body size and proportions of athletes have a long history. Comparisons of athletes within specific sports across time, though not extensive, indicate both positive and negative trends. The objective of the study was to evaluate secular variation in heights and weights of male youth soccer players reported in studies between 1978 and 2015. Reported mean ages, heights, and weights of male soccer players 9-18 years of age were extracted from the literature and grouped into two intervals: 1978-99 and 2000-15. A third-order polynomial was fitted to the mean heights and weights across the age range for each interval, while the Preece-Baines model 1 was fitted to the grand means of mean heights and mean weights within each chronological year to estimate ages at peak height velocity and peak weight velocity for each time interval. Third-order polynomials applied to all data points and estimates based on the Preece-Baines model applied to grand means for each age group provided similar fits. Both indicated secular changes in body size between the two intervals. Secular increases in height and weight between 1978-99 and 2000-15 were especially apparent between 13 and 16 years of age, but estimated ages at peak height velocity (13.01 and 12.91 years) and peak weight velocity (13.86 and 13.77 years) did not differ between the time intervals. Although the body size of youth soccer players increased between 1978-99 and 2000-15, estimated ages at peak height velocity and peak weight velocity did not change. The increase in height and weight likely reflected improved health and nutritional conditions, in addition to the selectivity of soccer reflected in systematic selection and retention of players advanced in maturity status, and exclusion of late maturing players beginning at about 12-13 years of age. Enhanced training programs aimed at the development of strength and power are probably an additional factor contributing to secular increases in body weight.

#2 A Study of Relationships among Technical, Tactical, Physical Parameters and Final Outcomes in Elite Soccer Matches as Analyzed by a Semiautomatic Video Tracking System
Reference: Percept Mot Skills. 2017 Jun;124(3):601-620. doi: 10.1177/0031512517692904. Epub 2017 Jan 1.
Authors: Filetti C, Ruscello B, D'Ottavio S, Fanelli V
Summary: The performance of a soccer team depends on many factors such as decision-making, cognitive and physical skills, and dynamic ever-changing space-time interactions between teammate and opponents in relation to the ball. Seventy ( n = 70) matches of the Italian SERIE A season 2013-2014 were investigated to analyze the mean performance of 360 players in terms of physical (physical efficiency index; PEI) and technical-tactical (technical efficiency index; TEI) standpoints. Using a semiautomatic video analysis system that has incorporated new parameters able to measure technical-tactical and physical efficiency (Patent IB2010/002593, 2011-ISA), the correlation between these new variables and how much it relates to the likelihood of winning were verified. Correlations between TEI and PEI were significant ( n = 140, r = .60, p < .001), and TEI showed a higher likelihood of winning than PEI factors ( p < .0001 vs. .0001, CI 95% [1.64, 3.00] vs. [1.28, 2.07]). Higher TEI and TEI + PEI differences between the teams were associated with a greater likelihood of winning, but PEI differences were not. Key performance indicators and this performance assessment method might be useful to better understand what determines winning and to assist the overall training process and match management.

#3 Postactivation potentiation in elite young soccer players
Reference: J Exerc Rehabil. 2017 Apr 30;13(2):153-159. doi: 10.12965/jer.1734912.456. eCollection 2017 Apr.
Authors: Titton A, Franchini E
Download link:
Summary: The aim of this study was to investigate the acute effects of 16 different combinations to cause the postactivation potentiation (PAP) in elite young soccer players. Squat exercise in 4 different intensities (40%, 60%, 80%, and 100% one-repetition maximum [1RM]) was performed and its effects were evaluated in the performance of countermovement jump (CMJ), after 4 different recovery times (1, 3, 5, and 10 min). For this purpose, 25 young soccer players, underwent five experimental sessions. At the first session the control to determine 1RM in half-squat was carried out. The following four experimental sessions were comprised of four intensity combinations with four different recovery intervals in order to perform the CMJ test later, randomly determined and with 30-min interval between each combination. The conditions were compared using an analysis of variance with repeated measurements, followed by Bonferroni test, using 5% significance level (P<0.05). The different intensities investigated did not provide significant increases in CMJ height, but significant differences were noted in recovery time, where, at CMJ maximum height, 1-min interval was better than after 3 min (P<0.05), 5, and 10 min (P<0.001). On the average jump performances, 1-min interval resulted in better results (P<0.001) compared to other intervals. The 10-min recovery resulted in poorer performances compared to the other intervals (P<0.001). Our results indicate that regardless the intensity used in the half-squat exercise with elite young soccer players, the 1-min recovery time was more appropriate to promote an increase in vertical jump.

#4 Assessing long-term return to play after hip arthroscopy in football players evaluating risk factors for good prognosis
Reference: Knee Surg Sports Traumatol Arthrosc. 2017 May 17. doi: 10.1007/s00167-017-4573-z. [Epub ahead of print]
Authors: Barastegui D, Seijas R, Alvarez-Diaz P, Rivera E, Alentorn-Geli E, Steinbacher G, Cusco X, Cugat R
Summary: Groin pain is the third most common disease in football players and has often been associated with hip pathology such as femoroacetabular impingement and labral lesions. Hip arthroscopy offers possibilities of function restoration via minimally invasive procedures. The aim of this study is to evaluate professional football player's injuries and their return to play after hip arthroscopy for FAI and labral injuries. Patients that underwent hip arthroscopy between 2009 and 2014 were selected retrospectively. From this population, only professional soccer players competing at national level were included (Tegner 10). Arthroscopic surgery was proposed in patients with persistent pain. All patients were assessed for VAS score preoperatively and at 3, 6, 12 and 24 months post-op. HOS (sport and DLA) and mHHS tests were performed at the same time periods. All patients were men with a mean age of 26.5 ± 7.1 years old. Preoperative VAS (7.4 ± 1.3), HOS ADL (67.7 ± 5.5), HOS sport (37.6 ± 18.7) and mHHS (72.5 ± 8.8) showed improved scores during long-term follow-up. Time to return to play was 10.8 months (SD ± 4.3), with range between 4 and 20 months. Mean follow-up was 45.4 ± 15.6 months (range from 26 to 72 months). No differences were observed between non-active and active patients at final follow-up with respect to chondral lesions, but significant differences were observed with reference to management of the labrum (p = 0.031), where a higher rate of labrectomies existed among inactive patients and a higher rate of suture among active patients. Hip arthroscopy is a safe procedure with very good return to play results, but for optimized return to football one should consider patient age at the time of surgery, the condition of the labrum and low scores on the Harris Hip Score (mHHS) and HOS (sport version) as predictive factors for poor prognosis. Level of evidence IV.

#5 A football player with an evident knee trauma
Reference: Ned Tijdschr Geneeskd. 2017;161(0):D1068. [Article in Dutch]
Authors: Goudriaan WA, Huis In 't Veld R, Hoogeslag RAG
Summary: A 22-year-old male presented with medial sided instability of the right knee three days after shooting a blocked ball. Physical examination, which is usually feasible in the acute phase, showed grade 3 laxity of the superficial medial collateral ligament. MRI confirmed a distal rupture, which needs repair within 2 weeks after onset.

#6 The functional movement test 9+ is a poor screening test for lower extremity injuries in professional male football players: a 2-year prospective cohort study
Reference: Br J Sports Med. 2017 May 16. pii: bjsports-2016-097307. doi: 10.1136/bjsports-2016-097307. [Epub ahead of print]
Authors: Bakken A, Targett S, Bere T, Eirale C, Farooq A, Tol JL, Whiteley R, Khan KM, Bahr R
Summary: The 9+ screening battery test consists of 11 tests to assess limitations in functional movement. The aim was to examine the association of the 9+ with lower extremity injuries and to identify a cut-off point to predict injury risk. Professional male football players in Qatar from 14 teams completed the 9+ at the beginning of the 2013/2014 and 2014/2015 seasons. Time-loss injuries and exposure in training and matches were registered prospectively by club medical staff during these seasons. Univariate and multivariate Cox regression analyses were used to calculate HR and 95% CI. Receiver operating characteristic (ROC) curves were calculated to determine sensitivity and specificity and identify the optimal cut-off point for risk assessment. 362 players completed the 9+ and had injury and exposure registration. There were 526 injuries among 203 players (56.1%) during the two seasons; injuries to the thigh were the most frequent. There was no association between 9+ total score and the risk of lower extremity injuries (HR 1.02, 95% CI 0.99 to 1.05, p=0.13), even after adjusting for other risk factors in a multivariate analysis (HR 1.01, 95% CI 0.98 to 1.04, p=0.37). ROC curve analysis revealed an area under the curve of 0.48, and there was no cut-off point that distinguished injured from non-injured players. The 9+ was not associated with lower extremity injury, and it was no better than chance for distinguishing between injured and uninjured players. Therefore, the 9+ test cannot be recommended as an injury prediction tool in this population.

#7 Community-level football injury epidemiology: traumatic injuries treated at Swedish emergency medical facilities
Reference: Eur J Public Health. 2017 May 16. doi: 10.1093/eurpub/ckx053. [Epub ahead of print]
Authors: Timpka T, Schyllander J, Stark Ekman D, Ekman R, Dahlstrom O, Hagglund M, Kristenson K, Jacobsson J
Summary: Despite the popularity of the sport, few studies have investigated community-level football injury patterns. This study examines football injuries treated at emergency medical facilities using data from three Swedish counties. An open-cohort design was used based on residents aged 0-59 years in three Swedish counties (pop. 645 520). Data were collected from emergency medical facilities in the study counties between 1 January 2007 and 31 December 2010. Injury frequencies and proportions for age groups stratified by sex were calculated with 95% confidence intervals (95% CIs) and displayed per diagnostic group and body location. Each year, more than 1/200 person aged 0-59 years sustained at least one injury during football play that required emergency medical care. The highest injury incidence was observed among adolescent boys [2009 injuries per 100 000 population years (95% CI 1914-2108)] and adolescent girls [1413 injuries per 100 000 population years (95% CI 1333-1498)]. For female adolescents and adults, knee joint/ligament injury was the outstanding injury type (20% in ages 13-17 years and 34% in ages 18-29 years). For children aged 7-12 years, more than half of the treated injuries involved the upper extremity; fractures constituted about one-third of these injuries. One of every 200 residents aged 0-59 years in typical Swedish counties each year sustained a traumatic football injury that required treatment in emergency healthcare. Further research on community-level patterns of overuse syndromes sustained by participation in football play is warranted.

#8 Determination of clinically relevant differences in frontal plane hop tests in women’s collegiate Basketball and soccer players
Reference: Int J Sports Phys Ther. 2017 Apr;12(2):182-189.
Authors: Hardesty K, Hegedus EJ, Ford KR, Nguyen AD, Taylor JB
Summary: ACL injury prevention programs are less successful in female basketball players than in soccer players. Previous authors have identified anthropometric and biomechanical differences between the athletes and different sport-specific demands, including a higher frequency of frontal plane activities in basketball. Current injury risk screening and preventive training practices do not place a strong emphasis on frontal plane activities. The medial and lateral triple hop for distance tests may be beneficial for use in the basketball population. The hypothesis is to 1) establish normative values for the medial and lateral triple hop tests in healthy female collegiate athletes, and 2) analyze differences in test scores between female basketball and soccer players. It was hypothesized that due to the frequent frontal plane demands of their sport, basketball players would exhibit greater performance during these frontal plane performance tests. Thirty-two NCAA Division-1 female athletes (20 soccer, 12 basketball) performed three trials each of a medial and lateral triple hop for distance test. Distances were normalized to height and mass in order to account for anthropometric differences. Repeated measures ANOVAs were performed to identify statistically significant main effects of sport (basketball vs. soccer), and side (right vs. left), and sport x side interactions. After accounting for anthropometric differences, soccer players exhibited significantly better performance than basketball players in the medial and lateral triple hop tests (p < 0.05). Significant side differences (p  = 0.02) were identified in the entire population for the medial triple hop test, such that participants jumped farther on their left (400.3 ± 41.5 cm) than right (387.9 ± 43.4 cm) limbs, but no side differences were identified in the lateral triple hop. No significant side x sport interactions were identified. Women's basketball players exhibit decreased performance of frontal plane hop tests when compared to women's soccer players. Additionally, the medial triple hop for distance test may be effective at identifying side-to-side asymmetries.

American Football
#1 Environmental and Physiological Factors Affect Football Head Impact Biomechanics
Reference: Med Sci Sports Exerc. 2017 May 15. doi: 10.1249/MSS.0000000000001325. [Epub ahead of print]
Authors: Mihalik JP, Sumrall AZ, Yeargin SW, Guskiewicz KM, King KB, Trulock SC, Shields EW
Summary: Recent anecdotal trends suggest a disproportionate number of head injuries in collegiate football players occur during preseason football camp. In warmer climates, this season also represents the highest risk for heat-related illness among collegiate football players. Since concussion and heat illnesses share many common symptoms, we need 1) to understand if environmental conditions, body temperature, and hydration status affect head impact biomechanics; and 2) to determine if an in-helmet thermistor could provide a valid measure of gastrointestinal temperature. A prospective cohort of 18 Division I college football players (age = 21.1 ± 1.4 yrs; height = 187.7 ± 6.6 cm; mass = 114.5 ± 23.4 kg). Data were collected during three experimental and one control session. During each session, the Head Impact Telemetry System recorded head impact biomechanics (linear acceleration, rotational acceleration, and severity profile) and in-helmet temperature. A wet bulb globe device recorded environmental conditions, and CorTemp Ingestible Core Body Temperature Sensor recorded gastrointestinal temperature. Our findings suggest that linear acceleration (P = 0.57), rotational acceleration (P = 0.16), and HITsp (P =0.33) are not influenced by environmental or physiological conditions. We did not find any single or combination of predictors for impact severity. Rotational acceleration was approaching significance between our early experimental sessions when compared to our control session. More research should be conducted to better understand if rotational accelerations are a component of impact magnitudes that are affected due to changes in environmental conditions, body temperature, and hydration status.





World Conference on Science and Soccer - Posters

Since Wednesday I have been at the World Conference on Science and Soccer at Rennes (France).

As part of every conference, delegates can submit their research as a poster that are hang up in a separate room for visitors.

Below are (nearly) all poster of the conference.






Latest research in football - week 19 - 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 Effects of Sleep Deprivation on Soccer Skills
Reference: Percept Mot Skills. 2017 Jan 1:31512517707412. doi: 10.1177/0031512517707412. [Epub ahead of print]
Authors: Pallesen S, Gundersen HS, Kristoffersen M, Bjorvatn B, Thun E, Harris A
Summary: Many athletes sleep poorly due to stress, travel, and competition anxiety. In the present study, we investigated the effects of sleep deprivation on soccer skills (juggling, dribbling, ball control, continuous kicking, 20 and 40 m sprint, and 30 m sprint with changes of direction). In all, 19 male junior soccer players (14-19 years old) were recruited and participated in a cross-balanced experimental study comprising two conditions; habitual sleep and 24 hours sleep deprivation. In both conditions, testing took place between 8 a.m. and 10 a.m. Order of tests was counterbalanced. Each test was conducted once or twice in a sequence repeated three times. The results revealed a negative effect of sleep deprivation on the continuous kicking test. On one test, 30 meter sprint with directional changes, a significant condition × test repetition interaction was found, indicating a steeper learning curve in the sleep deprived condition from Test 1 to Test 2 and a steeper learning curve in the rested condition from Test 2 to Test 3. The results are discussed in terms of limitations and strengths, and recommendations for future studies are outlined.

#2 The influence of a 12% carbohydrate-electrolyte beverage on self-paced soccer-specific exercise performance
Reference: J Sci Med Sport. 2017 Apr 21. pii: S1440-2440(17)30399-7. doi: 10.1016/j.jsams.2017.04.015. [Epub ahead of print]
Authors: Harper LD, Stevenson EJ, Rollo I, Russell M
Summary: The purpose was to assess the physiological and performance effects of a 12% carbohydrate-electrolyte beverage consumed at practically applicable time-points (i.e., before each half) throughout simulated soccer match-play. Fed players (n=15) performed 90-min of soccer-specific exercise (including self-paced exercise at the end of each half). Players consumed carbohydrate-electrolyte (CHO; 60g×500ml-1, Na+ 205mg×500ml-1), placebo-electrolyte (PL) or water (Wat) beverages at the end of the warm-up (250ml) and half-time (250ml plus ad-libitum water). Blood was drawn before each half and every 15-min during exercise. Physical (15-m sprinting, countermovement jumps, self-paced distance, acceleration/deceleration count), technical (dribbling) and cognitive (memory, attention, decision-making) performance was assessed. Ratings of perceived exertion (RPE) and abdominal discomfort were measured. Against Wat and PL, CHO increased (all p<0.05) mean accelerations >1.5m·s-2 during self-paced exercise (>+25%) and dribbling speed from 60-min onwards (>+3%). Mean sprinting speed improved (+2.7%) in CHO versus Wat. Blood glucose increased before and during each half in CHO versus PL and Wat (all p<0.05). A 27% decline in glycaemia occurred at 60-min in CHO. RPE was comparable between trials. Cognition reduced post-exercise (p<0.05); this decline was not attenuated by CHO. Abdominal discomfort increased during exercise but was similar between trials. Using more realistic fluid ingestion timings than have been examined previously, consuming a 12% carbohydrate-electrolyte beverage increased blood glucose, self-paced exercise performance, and improved dribbling speed in the final 30-min of exercise compared to water and placebo. Carbohydrates did not attenuate post-exercise reductions in cognition.

#3 Profile of match performance and heart rate response in Japanese amputee soccer
Reference: J Sports Med Phys Fitness. 2017 May 5. doi: 10.23736/S0022-4707.17.07246-2. [Epub ahead of print]
Authors: Maehana H, Miyamoto A, Koshiyama K, Tanaka Yanagiya T, Yoshimura M
Summary: The purpose of this study was to profile the match performance and heart rate response in Japanese amputee soccer. Twelve amputee soccer players participated in this study. Match data were collected 20 samples in 4 matches. Match performances data such as total distance, high-intensity running (HIR: ≥13km·h-1) were collected using a global positioning systems technology. Heart rate (HR) was recorded using short-range radio telemetry. In addition, the rating of perceived exertion (RPE) was assessed immediately using Borg's original after the first half and the second half. This study showed that the distance covered over the 50 minutes of the match was 2984.2±56.1m, and it was significantly shorter in the second half than the first half (p<0.05). The distance covered by HIR was 205.3±100.5m, and there was no significant difference between the first half and the second half. Moreover, the mean HR during match was 176.8±7.9beats·min-1, which corresponded to 96.3% of HRmax. RPE was a high value of more 15 in both of the first half and the second half. This study was the first to evaluate competitive performance during matches in amputee soccer. Results of this study indicated that the exercise intensity was high in amputee soccer. It would be considered that causes were amputee soccer own rules and exercise style. These findings would serve as the reference when advance the future studies of amputee soccer.

#4 Reliability of concentric and eccentric strength of hip abductor and adductor muscles in young soccer players
Reference: Biol Sport. 2015 Dec;32(4):351-356. doi: 10.5604/20831862.1189202. Epub 2015 Dec 29.
Authors: Gerodimos V, Karatrantou K, Paschalis V, Zafeiridis A, Katsareli E, Bilios P, Kellis S
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Summary: The concentric and eccentric strength profile and muscular balance of the hip joint are important parameters for success in soccer. This study evaluated the reliability for the assessment of hip abduction and adduction isokinetic strength over a range of angular velocities (30 and 90°/s) and types of muscular actions (concentric and eccentric) in young soccer players. The reliability for the assessment of reciprocal (conventional and functional) and bilateral torque ratios was also examined. Fifteen male soccer players (15±1 years) performed two sessions, separated by three days. The testing protocol consisted of five maximal concentric and eccentric hip abductions and adductions of both legs at angular velocities of 30°/s and 90°/s. The peak torque was evaluated in young soccer players using an isokinetic dynamometer (Cybex Norm), and the reciprocal strength ratios (conventional and functional) and bilateral ratios (non-preferred to preferred leg ratios) were calculated. The test-retest reliability for the assessment of peak torque (ICC = 0.71-0.92) and of reciprocal muscle group ratios (ICC = 0.44-0.87) was found to be moderate to high. Bilateral torque ratios exhibited low to moderate reliability (ICC = 0.11-0.64). In conclusion, isokinetic strength of hip abductor and adductor muscles and the conventional and functional strength ratios can be reliably assessed in young soccer players, especially at low angular velocities. The assessment, however, of bilateral strength ratios for hip abductor/adductor muscles should be interpreted with more caution.

#5 Implication of dynamic balance in change of direction performance in young elite soccer players is angle dependent?
Reference: J Sports Med Phys Fitness. 2017 Apr 26. doi: 10.23736/S0022-4707.17.06752-4. [Epub ahead of print]
Authors: Rouissi M, Haddad M, Bragazzi NL, Owen AL, Moalla W, Chtara M, Chamari K
Summary: Team sports require rapid whole body change of direction (COD) in order to regain, maintain possession of the ball or to avoid opponent. These actions are often performed through unilateral process, with the contralateral leg incurring no ground contact. As a result, maintaining unilateral dynamic balance remains important. The aim of this study was to examine the relationship between dynamic balance (DB) and (COD) performance in young elite soccer players. 20 right-footed young elite soccer players (age=16.42±0.55 year, height=176±2.5cm; leg length=95.70±3.34cm, body-mass=67.03±5.20kg) participated in this study. All players performed star excursion balance test (SEBT) with dominant (DL) and nondominant leg (NDL). 10m sprint with COD of 45°, 90°, 135° or 180° after 5m were also assessed with COD on both right and left sides. Correlations analysis showed significant negative relationships (moderate to high) between COD tests (with DL and NDL) and some selected reaching directions of the SEBT. Stepwise multiple regression analysis showed that DB performance explained between 20% and 75% of the variance of COD tests. Likewise, dynamic balance contribution was dependent upon the angle of COD and the leg used to turn. Some selected reaching directions of the SEBT were significantly correlated with COD's performance in young elite soccer players which, possibly due to similarities in movement demands and muscle recruitment. Furthermore, the contribution of dynamic balance on COD performance was angle dependent and individualized specific dynamic stability exercises may be required to compensate players' deficit in each COD angle.

#6 Effect of a specialized injury prevention program on static balance, dynamic balance and kicking accuracy of young soccer players
Reference: World J Orthop. 2017 Apr 18;8(4):317-321. doi: 10.5312/wjo.v8.i4.317. eCollection 2017 Apr 18.
Authors: Dunsky A, Barzilay I, Fox O
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Summary: The purpose was to study the effect of balance intervention program using the "FIFA 11+" program on static and dynamic balance and kicking accuracy of young soccer players. Twenty young soccer players were allocated to experimental (n = 10) or control (n = 10) groups. The experimental group performed the "FIFA 11+" program three times a week for six weeks. The control group performed their normal warm-up routine. The primary outcomes were measured pre and post intervention, and assessed kicking accuracy, static balance and dynamic balance. No differences were found in kicking accuracy following intervention, for both groups, however, static balance improved significantly among the experimental group with significant interaction with the control group, and with high effect size. In addition, the dynamic balance of the left leg of the experimental group, with medium effect size for interaction between groups. The large effect size of balance improvement that was observed following six weeks of intervention sessions, implies that soccer trainers and coaches should consider the inclusion of "FIFA 11+" as components of programs aimed at improving balance ability/control in young soccer players, as improvement in balance abilities may prevent injuries.

#7 In Place But Not Always Used: Automated External Defibrillators in Amateur Football
Reference: Curr Sports Med Rep. 2017 May/Jun;16(3):126-128. doi: 10.1249/JSR.0000000000000352.
Authors: Vernooij RWM, Goedhart E, Pardo-Hernandez H.

#8 Thunderstorm Asthma, Relative Anemia, and Football Carnage
Reference: Curr Sports Med Rep. 2017 May/Jun;16(3):116-117. doi: 10.1249/JSR.0000000000000349.
Authors: Eichner ER.

#9 Incidence of injury and illness in South African professional male football players: a prospective cohort study
Reference: J Sports Med Phys Fitness. 2017 May 9. doi: 10.23736/S0022-4707.17.07452-7. [Epub ahead of print]
Authors: Bayne H, Schwellnus M, Janse Van Rensburg D, Botha J, Pillay L
Summary: Medical illnesses and sports-related injuries both have an effect on athlete health and performance. Epidemiology of injury and illness has been extensively researched during international football tournaments and the European football season. Reports on injury location and severity differ across geographical regions, and there is limited information on injury epidemiology in African football leagues. No studies have investigated the illness burden in football in Africa. This was a prospective cohort study involving two football teams over the 10- month duration of the 2015/16 Premier Soccer League in South Africa. Team medical staff recorded daily football exposure, illness and injuries. Team-based match and training exposure was calculated and used to determine injury and illness incidence and burden over the football season. Overall injury incidence was 2.2 / 1000 h, with match injury incidence of 24.8 / 1000 h and training injury incidence of 0.9 / 1000 h. Time loss injuries accounted for 33 of the 44 injuries recorded. The most common time loss injury location was the knee (14 injuries, 42%). There were 7 minimal, 4 mild, 12 moderate and 10 severe injuries. Sprain/ligament injury (8 injuries) was the most common type, followed by meniscus/cartilage injury (7 injuries). Eleven illnesses were reported during the season, with an incidence of 0.7 / 1000 player days, and most were minimal in severity (8/11). The illness burden was 1.7 / 1000 player days. The respiratory (46%) and gastrointestinal (36%) systems were most commonly affected. The incidence of injury was comparable with data reported internationally and mirrors the increased risk of injury during matches versus training. The nature of injury differed in that the knee was more frequently affected than the ankle or thigh, joint injuries were more common than muscle injuries, and there was a larger proportion of severe injuries. The illness burden was very low.

#10 Intra-system reliability of SICS: video-tracking system (Digital.Stadium®) for performance analysis in football
Reference: J Sports Med Phys Fitness. 2017 May 9. doi: 10.23736/S0022-4707.17.07267-X. [Epub ahead of print]
Authors: Beato M, Jamil M
Summary: The correct evaluation of external load parameters is a key factor in professional football. The instrumentations usually utilised to quantify the external load parameters during official matches are Video-Tracking Systems (VTS). VTS is a technology that records two- dimensional position data (x and y) at high sampling rates (over 25 Hz). The aim of this study was to evaluate the intra-system reliability of Digital.Stadium® VTS. 28 professional male football players taking part in the Italian Serie A (age 24 ± 6 years, body mass 79.5 ± 7.8 kg, stature 1.83 ± 0.05 m) during the 2015/16 season were enrolled in this study (Team A and Team B). Video-analysis was done during an official match and data analysis was performed immediately after the game ended and then replicated a week later. This study reported a near perfect relationship between the initial analysis (analysis 1) and the replicated analysis undertaken a week later (analysis 2). R2 coefficients were highly significant for each of the performance parameters, p < 0.001. This study reported a mean TD = 8095 ± 3271 and 8073 ± 3263 m in analysis 1 and analysis 2, respectively. Players reported a mean distance covered over 25 w kg-1 equivalent to 1304 ± 673 m and 1294 ± 672 m, and they reported a mean metabolic power of 9.65 ± 1.64 w kg-1 and 9.58 ± 1.61 w kg-1, in analysis 1 and analysis 2, respectively. The findings reported in this study underlined that all data reported by Digital.Stadium® VTS showed high levels of absolute and relative reliability.

#11 Quantitative T2 * relaxation time analysis of articular cartilage of the tibiotalar joint in professional football players and healthy volunteers at 3T MRI
Reference: J Magn Reson Imaging. 2017 May 9. doi: 10.1002/jmri.25757. [Epub ahead of print]
Authors: Behzadi C, Maas KJ, Welsch G, Kaul M, Schoen G, Laqmani A, Adam G, Regier M
Summary: The purpose was to compare T2 * relaxation times of the tibiotalar cartilage between professional football players and matched healthy male volunteers. Twenty-two ankles of professional football players (24.3 ± 3.8 years) and 20 age- and body mass index-matched healthy individuals (25.6 ± 2.4 years) were investigated. The study protocol consisted of multiplanar T1 -weighted, fat-saturated proton-density weighted (Pdw) and a 3D multiecho T2 * sequence with 22 echo times (4.6-53.6 msec). The articular cartilage was subdivided into six segments. Regions of interest were manually drawn in three zones (lateral, central, medial). Differences and confidence intervals were estimated applying a random effects models. Fixed effects were professional football players versus healthy individuals and areas. The random effect was defined as the person cluster of the different individuals. T2 * values were significantly prolonged in football players compared to male volunteers in all predefined cartilage segments (mean, 17.5 vs. 15.5 msec; P < 0.001). In both groups, the highest relaxation times were found in the lateral zone, with statistically higher relaxation times in professional football players (18.5 vs. 16.5 msec, P = 0.003). Separate evaluation revealed the longest relaxation times in the posterior tibiotalar cartilage, with 21.0 msec for professional football players compared to 19.4 msec for healthy volunteers (P = 0.064). Based on these initial results, T2 * values of the tibiotalar cartilage seem to be elevated in professional football players compared to healthy volunteers. Prospective longitudinal studies should be encouraged to show if these results represent early subtle cartilage lesions prior to clinical manifestation or rather temporary adaptation related to daily high-level loading.

#12 Public opinion on alcohol consumption and intoxication at Swedish professional football events

Reference: Subst Abuse Treat Prev Policy. 2017 May 8;12(1):21. doi: 10.1186/s13011-017-0103-8.
Authors: Skoglund C, Durbeej N, Elgan TH, Gripenberg J
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Summary: Alcohol-related problems at professional sporting events are of increasing concern and alarming reports are often reported in international media. Although alcohol consumption increases the risk for interpersonal violence, it is viewed as a focal element of large football events. Sweden has a long tradition of high public support for strict alcohol-control policies. However, little is known about public opinions on alcohol intoxication and the support for interventions to decrease intoxication at football events. The current study explored the public opinion towards alcohol use, intoxication and alcohol policies at professional football matches in Sweden. A cross-sectional design was utilized and a random general population sample of 3503 adult Swedish residents was asked to participate in a web survey during 2016 (response rate 68%). In total, 26% of the respondents supported alcohol sales at football events. Over 90% reported that obviously intoxicated spectators should be denied entrance or evicted from arenas. The support for regulations limiting alcohol availability varied with background factors such as gender, alcohol use and frequency of football event attendance.There is a strong public consensus for strategies and policies to reduce alcohol sales and intoxication levels at football matches. This public support has implications for our preventive efforts and will facilitate the implementation of strategies and policy changes.

American Football
#1 The Effect of the Number of Carries Among College Running Backs on Future Injury Risk and Performance in the National Football League

Reference: Orthop J Sports Med. 2017 Apr 21;5(4):2325967117703054. doi: 10.1177/2325967117703054. eCollection 2017 Apr.
Authors: Kraeutler MJ1, Belk JW1, McCarty EC1.
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Summary: There has been speculation that running backs with an excessive number of carries in college are less likely to be successful in the National Football League (NFL). The purpose was to determine whether there is a correlation between number of carries by college running backs and future performance and injury risk in the NFL. Using the ESPN archives of National Collegiate Athletic Association and NFL running backs, the following inclusion criteria were used: running backs who played their last college season from 1999 through 2012 and who were drafted in the first 4 rounds of the NFL draft following their college career. Players were grouped by number of carries during their final college season (group A, 100-200 carries; group B, 250+ carries). Performance and injury risk were compared between groups during the first 3 eligible seasons in the NFL. Groups were compared based on total number of carries, mean yards per carry, number of games missed due to injury, and the specific injuries resulting in missed playing time. During the seasons studied, a total of 103 running backs were included (group A, n = 42; group B, n = 61). There was a trend toward a significantly greater mean total number of carries through 3 NFL seasons in group B (group A, n = 276 carries; group B, n = 376 carries; P = .058). Mean yards per carry did not differ between groups (group A, n = 3.9 yards/carry; group B, n = 4.0 yards/carry; P = .67). Groups A and B missed a mean 5.8 and 5.7 games, respectively, due to injury during their first 3 NFL seasons (P = .98). A significantly greater proportion of players in group A suffered a concussion compared with group B (P = .014). There is no correlation between the number of carries by college running backs and future injury risk or performance during their early NFL career.

#2 Concussion mechanisms and activities in youth, high school, and college football
Reference: J Neurotrauma. 2017 May 10. doi: 10.1089/neu.2017.5032. [Epub ahead of print]
Authors: Lynall RC, Campbell KR, Wasserman EB, Dompier TP, Kerr Z
Summary: Our purpose was to determine concussion mechanism and activity differences between 3 cohorts of football players; youth, high school, and college. Participants in this prospective cohort study included youth (ages 5-14, 118 teams, 310 team-seasons), high school (96 teams, 184 team-seasons), and college (34 teams, 71 team-seasons) football players. Athletic trainers collected athlete-exposure (AE) and concussion data during the 2012-2014 seasons. Injury mechanism referred to the object that made contact with the concussed player, resulting in the concussion. Injury activity referred to the type of football specific activity the player was involved in when the concussion was sustained. Injury proportion ratios (IPR) compared distributions of concussion mechanisms and activities among age levels. 1,429 concussions were reported over 1,981,284 AE across all levels (Rate: 0.72/1000AE). Overall, most concussions were due to player contact (84.7%). During games, a greater proportion of youth football concussions (14.7%) were due