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.

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