Latest research in football - week 6 - 2018

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 Effect of cluster set warm-up configurations on sprint performance in collegiate male soccer players
Reference: Appl Physiol Nutr Metab. 2018 Jan 24. doi: 10.1139/apnm-2017-0610. [Epub ahead of print]
Authors: Nickerson BS, Mangine GT, Williams TD, Martinez IA
Summary: The purpose of this study was to determine if back squat cluster sets (CS) with varying inter-repetition rest periods would potentiate greater sprint performance compared to a traditional set parallel back squat in collegiate soccer players. Twelve collegiate male soccer players (21.0 ± 2.0 years; 180.0 ± 9.0 cm; 79.0 ± 9.5 kg) performed a 20-meter sprint prior to (PRE) a potentiation complex and at 1-, 4-, 7-, and 10-minutes post-exercise on three separate, randomized occasions. On each occasion, the potentiation complex consisted of 1 set of 3 repetitions at 85% one-repetition maximum (1RM) for the traditional parallel back squat. However, on one occasion the 3-repetition set was performed in a traditional manner (i.e., continuously), whereas on the other two occasions, 30- (CS30) and 60-seconds (CS60) of rest were allotted between each repetition. Repeated measures analysis of variance revealed greater (p = 0.022) mean barbell velocity on CS60 compared to the traditional set. However, faster (p < 0.040) 20-meter sprint times were observed for CS30 (3.15±0.16 sec) compared to traditional (3.20±0.17 sec) only at 10-minutes post-exercise. No other differences were observed. These data suggest that a single cluster set of three repetitions with 30-second inter-repetition rest periods at 85% 1RM acutely improves 20-meter sprinting performance. Strength and conditioning professionals and their athletes might consider its inclusion during the specific warm-up to acutely improve athletic performance during the onset (≤ 10 minutes) of training or competition.

#2 The Effects of Cupping on Hamstring Flexibility in Collegiate Soccer Players
Reference: J Sport Rehabil. 2018 Jan 24:1-18. doi: 10.1123/jsr.2017-0199. [Epub ahead of print]
Authors: Williams JG, Gard HI, Gregory JM, Gibson A, Austin J
Summary: Collegiate soccer players suffer hamstring injuries due to inflexibility and repetitive motions involving intense hamstring lengthening and contraction during sport. Although a popular intervention for muscular injury, there exists limited evidence of the effects of therapeutic cupping on hamstring flexibility. The objective was to determine the effect of cupping therapy on hamstring flexibility in collegiate soccer players. Twenty-five, asymptomatic, NCAA Division III soccer players (10 males, 15 females) (age = 19.4 ± 1.30 years, height = 175.1 ± 8.2 cm, mass = 69.5 ± 6.6 kg) participated in this study.  A 7-minute therapeutic cupping treatment was delivered to the treatment group. Four 2-inch cups were fixed atop trigger point locations within the hamstring muscle bellies of participants' dominant legs. Control group participants received no intervention between pre- and post-test measurements. Pretest and posttest measurements of hamstring flexibility, using a Passive Straight Leg Raise (PSLR), were performed on both groups were used as outcome measures. PSLR measurements were conducted by blinded examiners using a digital inclinometer. An independent samples t-test was used to analyze changes in hamstring flexibility from pre- to post-treatment with p-values set a priori at 0.05. An independent samples t-test demonstrated no significant difference in change in hamstring flexibility between participants in the treatment group and those in the control group (t23 = -.961, p = .35). The findings of this study demonstrated no statistically significant changes in hamstring flexibility following a cupping treatment.

#3 Reliability of internal and external load parameters in recreational football (soccer) for health
Reference: Res Sports Med. 2018 Jan 24:1-7. doi: 10.1080/15438627.2018.1431532. [Epub ahead of print]
Authors: Beato M, Jamil M, Devereux G
Summary: There is limited research focussed around the analysis of internal and external load parameters during football health programmes. The aim of this study was to assess the reliability of internal and external load parameters in this activity. Thrity subjects were enrolled (mean ± SDs; age = 43 ± 3 years, weight = 84 ± 14 kg, height = 176 ± 7 cm, BMI = 27.1 ± 3, VO2max = 40.7 ± 3.4 The football matches (five a-side) took place on an artificial grass outdoor field (pitch size of 36 × 18.5 m). Participants completed the match (60 min) and replicated the same match a week later. The analysis took into account several parameters: heart rate (HR), total distance (TD), high speed running (HSR), number of accelerations (>2 m.s-2) and metabolic power (MP). We found a good score of reliability in several parameters: TD (ICC = 0.66), accelerations (ICC = 0.62), mean HR (ICC = 0.82), HSR (ICC = 0.77) and MP (ICC = 0.66). The results reported in this study revealed good scores of absolute reliability and small/trivial effect size.

#4 Activity monitoring in men's college soccer: a single season longitudinal study
Reference: Res Sports Med. 2018 Jan 23:1-13. doi: 10.1080/15438627.2018.1431535. [Epub ahead of print]
Authors: Slater LV, Baker R, Weltman AL, Hertel J, Saliba SA, Hart JM
Summary: Performance in soccer has been characterized previously using time-motion analyses; however, it is unclear if men's college soccer shares performance characteristics with women's college or men's professional soccer. The purpose of this study was to compare proportions of matches spent walking, jogging, running, and sprinting in men's college soccer. Twenty-two male college soccer players wore global positioning system units during matches. Proportions of walking, jogging, running, high-speed running, and sprinting were calculated for each player based on time period (first half, second half, extra time) and outcome (win, loss, tie). Multivariate analyses of variance were run for each time period to compare positions. Means, 95% confidence intervals, and effect sizes were calculated for each position based on time period and match outcome. There were differences in low-speed and high-speed activities based on position, with forwards and midfielders demonstrating increased high-speed activities. Positional differences may require different physiological profiles and should be a consideration during training.

#5 Noninvasive Ventilation in Hypoxemic Patients: an Ongoing Soccer Game or a Lost One?
Reference: Turk J Anaesthesiol Reanim. 2017 Dec;45(6):329-331. doi: 10.5152/TJAR.2017.241102. Epub 2017 Dec 1.
Authors: Gregoretti C, Cortegiani A, Raineri SM, Giarrjatano A
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#6 Acute Effects of Ballistic vs Passive Static Stretching Involved in A Pre-Match Warm-Up Regarding Vertical Jump and Linear Sprint Performance in Soccer Players
Reference: J Strength Cond Res. 2018 Jan 30. doi: 10.1519/JSC.0000000000002477. [Epub ahead of print]
Authors: Mariscal SL, Garcia VS, Fernandez-Garcia JC, Saez de Villarreal E
Summary: The purpose of this study was to compare the effects of introducing passive static and ballistic stretching in a standard soccer match warm-up. The variables addressed were the Counter Movement Jump (CMJ), Abalakov jump and the 40 m linear sprint. The sample was composed of 33 male subjects, divided in two age groups. U16 and adult players formed the groups, in order to cross check if there were differences between them. Each group was further subdivided into two groups regarding the type of stretching carried out during the stretching phase. Prior to the warm-up, the tests previously described were assessed. In the experimental phase, standard stretching was carried out consisting of: an initial phase in which players had to execute continuous running; a general phase in which players had to make articulate moves; a technical phase, in which players had to execute exercises with the ball; a 5 vs. 5 small sided game was carried out during the tactical phase; and, in the final phase, activation exercises and sprints were carried out by the players. Eventually, the same variables were assessed again once the warm-up was finished. There were no statistically significant differences between the two types of stretching included in the pre-match warm-up. It can be concluded that ballistic and passive static stretching (<10s) did not cause, under these circumstances, any effect in the assessed variables related to soccer performance (linear sprint, CMJ and Abalakov). This has to be considered by coaches when devising soccer related warm-ups.

#7 Optimal Reactive Strength Index: Is it an Accurate Variable to Optimize Plyometric Training Effects on Measures of Physical Fitness in Young Soccer Players?
Reference: J Strength Cond Res. 2018 Jan 30. doi: 10.1519/JSC.0000000000002467. [Epub ahead of print]
Authors: Ramirez-Campillo R, Alvarez C, Garcia-Pinillos F, Sanchez-Sanchez J, Yanci J, Castillo D, Loturco I, Chaabene H, Moran J, Izquierdo M
Summary: This study aimed to compare the effects of drop-jump training using a fixed drop-box height (i.e., 30-cm [FIXED]) versus an optimal drop-box height (i.e, 10-cm to 40-cm: generating an optimal [OPT] reactive strength index [RSI]) in youth soccer players' physical fitness. Athletes were randomly allocated to a control-group (CG: n=24; age=13.7 years), a fixed drop-box height group (FIXED, n=25; age=13.9 years) or an optimal drop-box height group (OPT, n=24; age=13.1 years). Before and after 7 weeks of training, tests for the assessment of jumping (countermovement jump [CMJ], five multiple bounds [MB]), speed (20-m sprint time), change of direction (Illinois change of direction test [CODT]), strength (RSI and 5 maximal squat repetition test [5RM]), endurance (2.4 km time trial), and kicking ability (maximal kicking distance) were undertaken. Analyses revealed main effects of time for all dependent variables (p<0.001, d=0.24-0.72), except for 20-m sprint time. Analyses also revealed group×time interactions for CMJ (p<0.001, d=0.51), DJ (p<0.001, d=0.30), 20-m sprint time (p<0.001, d=0.25), CODT (p<0.001, d=0.22), and 5RM (p<0.01, d=0.16). Post-hoc analyses revealed increases for the FIXED group (CMJ: 7.4%, d=0.36; DJ: 19.2%, d=0.49; CODA: -3.1%, d=-0.21; 5RM: 10.5%, d=0.32) and the OPT group (CMJ: 16.7%, d=0.76; DJ: 36.1%, d=0.79; CODA: -4.4%, d=-0.34; 5RM: 18.1%, d=0.47). Post-hoc analyses also revealed increases for the OPT group in 20-m sprint time (-3.7%, d=0.27). Therefore, to maximize the effects of plyometric training, an OPT approach is recommended. However, using adequate fixed drop-box heights may provide a rational and practical alternative.

#8 Accuracy, intra- and inter-unit reliability, and comparison between GPS and UWB-based position-tracking systems used for time-motion analyses in soccer
Reference: Eur J Sport Sci. 2018 Jan 31:1-8. doi: 10.1080/17461391.2018.1427796. [Epub ahead of print]
Authors: Bastida Castillo A, Gomez Carmona CD, De la Cruz Sanchez E, Pino Ortega J
Summary: There is interest in the accuracy and inter-unit reliability of position-tracking systems to monitor players. Research into this technology, although relatively recent, has grown exponentially in the last years, and it is difficult to find professional team sport that does not use Global Positioning System (GPS) technology at least. The aim of this study is to know the accuracy of both GPS-based and Ultra Wide Band (UWB)-based systems on a soccer field and their inter- and intra-unit reliability. A secondary aim is to compare them for practical applications in sport science. Following institutional ethical approval and familiarization, 10 healthy and well-trained former soccer players (20 ± 1.6 years, 1.76 ± 0.08 cm, and 69.5 ± 9.8 kg) performed three course tests: (i) linear course, (ii) circular course, and (iii) a zig-zag course, all using UWB and GPS technologies. The average speed and distance covered were compared with timing gates and the real distance as references. The UWB technology showed better accuracy (bias: 0.57-5.85%), test-retest reliability (%TEM: 1.19), and inter-unit reliability (bias: 0.18) in determining distance covered than the GPS technology (bias: 0.69-6.05%; %TEM: 1.47; bias: 0.25) overall. Also, UWB showed better results (bias: 0.09; ICC: 0.979; bias: 0.01) for mean velocity measurement than GPS (bias: 0.18; ICC: 0.951; bias: 0.03).

#9 Osteoarthritis of the hip and knee in former male professional soccer players
Reference: Br Med Bull. 2018 Jan 29. doi: 10.1093/bmb/ldy001. [Epub ahead of print]
Authors: Petrillo S, Papalia R, Maffulli N, Volpi P, Denaro V
Summary: Professional soccer (PS) players are at great risk of osteoarthritis (OA) of the knee and hip. Sources of data: Following the PRISMA guidelines, the key words 'osteoarthritis' and 'soccer' or 'football' were matched with 'players' or 'former' or 'retired' and with 'hip' or 'knee' on December 24, 2017 in the following databases: PubMed, Cochrane, Google scholar, Embase and Ovid. Only comparative studies reporting the prevalence rate of OA of both hip and knee joint in former PS athletes (fPSa) and age and sex matched controls were considered. In fPSa, the prevalence rate of OA of both hip and knee is significantly higher compared to age and sex matched controls. The pathological pathways responsible for the development of OA of the hip and knee in PS athletes (PSa) are still not clearly understood. The prevalence rate of clinical OA of the hip was 8.6% in fPSa and 5.6% in controls (odd ratio (OR) = 1.5; 95% CI: 1.06-2.31). The radiographic rate of OA was 21.2% in fPSa and 9.8% in controls (OR = 2.4; 95% CI: 1.66-3.69). A total of 14.6 and 53.7% of fPSa presented clinical and radiographic signs of OA of the knee, respectively, vs 12.9% (OR = 1.16; 95% CI: 0.86-1.55) and 31.9% (OR = 2.47; 95% CI: 2.03-3.00) of controls. Sonographic evidence of OA of the knee was found in 52% of fPSa and 33% of controls (OR = 2.2; 95% CI: 1.24-3.89). Preventive training programmes should be developed to reduce the number of fPSa presenting early OA.

#10 Key team physical and technical performance indicators indicative of team quality in the soccer Chinese super league
Reference: Res Sports Med. 2018 Jan 31:1-10. doi: 10.1080/15438627.2018.1431539. [Epub ahead of print]
Authors: Yang G, Leicht AS, Lago C, Gomez MA
Summary: The aim of this study was to identify the key physical and technical performance variables related to team quality in the Chinese Super League (CSL). Teams' performance variables were collected from 240 matches and analysed via analysis of variance between end-of-season-ranked groups and multinomial logistic regression. Significant physical performance differences between groups were identified for sprinting (top-ranked group vs. upper-middle-ranked group) and total distance covered without possession (upper and upper-middle-ranked groups and lower-ranked group). For technical performance, teams in the top-ranked group exhibited a significantly greater amount of possession in opponent's half, number of entry passes in the final 1/3 of the field and the Penalty Area, and 50-50 challenges than lower-ranked teams. Finally, time of possession increased the probability of a win compared with a draw. The current study identified key performance indicators that differentiated end-season team quality within the CSL.

#11 Influence of well-being variables and recovery state in physical enjoyment of professional soccer players during small-sided games
Reference: Res Sports Med. 2018 Jan 28:1-12. doi: 10.1080/15438627.2018.1431540. [Epub ahead of print]
Authors: Selmi O, Goncalves B, Ouergui I, Sampaio J, Bouassida A
Summary: This study aimed to assess the effects of the total quality of recovery and well-being indices (self-ratings of sleep during the preceding night, stress, fatigue and delayed onset muscle soreness) on rating of perceived exertion (RPE) and physical enjoyment (PE) during small-sided games. A total of 20 professional soccer players (25 ± 0.8 years) completed four 5-a-side game sessions of 25-min duration each (4 × 4 min work with 3-min passive recovery in-between). All variables were collected before each game session with the exception of RPE and Physical Activity Enjoyment Scale that were collected after. The results demonstrate that recovery state and pre-fatigue states were not contributing signals of affected internal intensity and enjoyment of players. The study established the objectivity and utility of RPE as a useful tool for determining internal intensity during soccer-specific training as well as PE for assessing emotional response during exercise or training session.

#12 Effects of Soccer Training on Anthropometry, Body Composition, and Physical Fitness during a Soccer Season in Female Elite Young Athletes: A Prospective Cohort Study
Reference: Front Physiol. 2017 Dec 22;8:1093. doi: 10.3389/fphys.2017.01093. eCollection 2017.
Authors: Lesinski M, Prieske O, Helm N, Granacher U
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Summary: The objectives of this study were to (i) describe soccer training (e.g., volume, types), anthropometry, body composition, and physical fitness and (ii) compute associations between soccer training data and relative changes of anthropometry, body composition, and physical fitness during a soccer season in female elite young athletes. Seasonal training (i.e., day-to-day training volume/types) as well as variations in anthropometry (e.g., body height/mass), body composition (e.g., lean body/fat mass), and physical fitness (e.g., muscle strength/power, speed, balance) were collected from 17 female elite young soccer players (15.3 ± 0.5 years) over the training periods (i.e., preparation, competition, transition) of a soccer season that resulted in the German championship title in under-17 female soccer. Training volume/types, anthropometrics, body composition, and physical fitness significantly varied over a soccer season. During the two preparation periods, higher volumes in resistance and endurance training were performed (2.00 ≤ d ≤ 18.15; p < 0.05), while higher sprint and tactical training volumes were applied during the two competition periods (2.22 ≤ d ≤ 11.18; p < 0.05). Body height and lean body mass increased over the season (2.50 ≤ d ≤ 3.39; p < 0.01). In terms of physical fitness, significant performance improvements were found over the soccer season in measures of balance, endurance, and sport-specific performance (2.52 ≤ d ≤ 3.95; p < 0.05). In contrast, no statistically significant changes were observed for measures of muscle power/endurance, speed, and change-of-direction speed. Of note, variables of muscle strength (i.e., leg extensors) significantly decreased (d = 2.39; p < 0.01) over the entire season. Our period-specific sub-analyses revealed significant performance improvements during the first round of the season for measures of muscle power/endurance, and balance (0.89 ≤ d ≤ 4.01; p < 0.05). Moreover, change-of-direction speed significantly declined after the first round of the season, i.e., transition period (d = 2.83; p < 0.01). Additionally, significant medium-to-large associations were observed between training and anthropometrics/body composition/physical fitness (-0.541 ≤ r ≤ 0.505). Soccer training and/or growth/maturation contributed to significant variations in anthropometry, body composition, and physical fitness outcomes throughout the different training periods over the course of a soccer season in female elite young soccer players. However, changes in components of fitness were inconsistent (e.g., power, speed, strength). Thus, training volume and/or types should be carefully considered in order to develop power-, speed- or strength-related fitness measures more efficiently throughout the soccer season.

#13 Orthopaedics injuries in male professional football players in Brazil: a prospective comparison between two divisions
Reference: Muscles Ligaments Tendons J. 2018 Jan 10;7(3):524-531. doi: 10.11138/mltj/2017.7.3.524. eCollection 2017 Jul-Sep.
Authors: Arliani GG, Lara PHS, Astur DC, Pedrinelli A, Pagura JR, Cohen M
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Summary: Football is a high-speed contact sport and the risk of injury is high. The objective of this study was to compare the two main divisions (A1 and A2) of the São Paulo Football Championship and to perform a correlation analysis of the variables studied. A prospective study was conducted using an electronic questionnaire previously developed by the Medical Committee of the São Paulo Football Federation. The questionnaire was sent to the doctors of the teams playing in the A1 and A2 divisions of the São Paulo Football Championship after each round. Setting: 2016 São Paulo Football Championship. The comparison of divisions A1 and A2 showed few significant differences among the various variables analysed in this study. The only significant differences were for right-side involvement in division A1 (p=0.044) and morning matches in division A2 (p<0.001). The correlation analysis of the variables studied showed expected associations, including sprains with a higher rate of need for surgery, ultrasound with muscle strains and moderate severity (8-28 days lost) with muscle strains. Despite the differences between the two divisions regarding budgets and team characteristics, there was a little difference in the variables analysed and there were associations such as sprains with a higher rate of need for surgery, ultrasound with muscle strains and moderate severity (8-28 days lost) with muscle strains.


American Football
#1 Incidence, Severity, and Time Loss Associated With Collegiate Football Fractures, 2004-2005 to 2013-2014
Reference: Am J Sports Med. 2018 Jan 1:363546517749914. doi: 10.1177/0363546517749914. [Epub ahead of print]
Authors: Cairns MA, Hasty EK, Herzog MM, Ostrum RF, Kerr ZY
Summary: The inherent risk of any time loss from physical injury in football has been extensively discussed, with many such injuries having a profound effect on the lives of National Collegiate Athletic Association (NCAA) football players. However, the incidence of fractures in collegiate football has not been well established. The purpose of the study was to examine the epidemiology of fractures in NCAA football. Fracture data reported in college football during the 2004-2005 to 2013-2014 academic years were analyzed from the NCAA Injury Surveillance Program (NCAA-ISP). Fracture rates per 1000 athlete-exposures, surgery and time loss distributions, injury rate ratios, injury proportion ratios (IPRs), and 95% CIs were reported. Overall, 986 fractures were reported. The rate of competition fractures was larger than the rate of practice fractures (1.80 vs 0.17 per 1000 athlete-exposures; injury rate ratio = 10.56; 95% CI, 9.32-11.96). Fractures of the hand/fingers represented 34.6% of all injuries, while fibula fractures (17.2%) were also common. A majority (62.5%) of all fractures resulted in time loss >21 days. Altogether, 34.4% of all fractures required surgery, and 6.3% were recurrent. The proportion of fractures resulting in time loss >21 days was higher for fractures requiring surgery than fractures not requiring surgery (85.0% vs 50.7%; IPR = 1.68; 95% CI, 1.53-1.83). The proportion of recurrent and nonrecurrent fractures requiring surgery did not differ (35.5% vs 34.3%; IPR = 1.03; 95% CI, 0.73-1.46); however, recurrent fractures were more likely to require surgery than nonrecurrent fractures when restricted to the hand/fingers (66.7% vs 27.2%; IPR = 2.45; 95% CI, 1.36-4.44). Fractures in collegiate football were sustained at a higher rate in competition than practice and frequently required extended time lost from participation, particularly among those requiring surgery. Prevention strategies are warranted to reduce incidence and severity of fractures.

#2 Association Between Playing American Football in the National Football League and Long-term Mortality
Reference: JAMA. 2018 Feb 1. doi: 10.1001/jama.2018.0140. [Epub ahead of print]
Authors: Venkataramani AS, Gandhavadi M, Jena AB
Summary: Studies of the longevity of professional American football players have demonstrated lower mortality relative to the general population but they may have been susceptible to selection bias. The objective was to examine the association between career participation in professional American football and mortality risk in retirement. Retrospective cohort study involving 3812 retired US National Football League (NFL) players who debuted in the NFL between 1982 and 1992, including regular NFL players (n = 2933) and NFL "replacement players" (n = 879) who were temporarily hired to play during a 3-game league-wide player strike in 1987. Follow-up ended on December 31, 2016. NFL participation as a career player or as a replacement player. The primary outcome was all-cause mortality by December 31, 2016. Cox proportional hazards models were estimated to compare the observed number of years from age 22 years until death (or censoring), adjusted for birth year, body mass index, height, and position played. Information on player death and cause of death was ascertained from a search of the National Death Index and web-based sources. Of the 3812 men included in this study (mean [SD] age at first NFL activity, 23.4 [1.5] years), there were 2933 career NFL players (median NFL tenure, 5 seasons [interquartile range {IQR}, 2-8]; median follow-up, 30 years [IQR, 27-33]) and 879 replacement players (median NFL tenure, 1 season [IQR, 1-1]; median follow-up, 31 years [IQR, 30-33]). At the end of follow-up, 144 NFL players (4.9%) and 37 replacement players (4.2%) were deceased (adjusted absolute risk difference, 1.0% [95% CI, -0.7% to 2.7%]; P = .25). The adjusted mortality hazard ratio for NFL players relative to replacements was 1.38 (95% CI, 0.95 to 1.99; P = .09). Among career NFL players, the most common causes of death were cardiometabolic disease (n = 51; 35.4%), transportation injuries (n = 20; 13.9%), unintentional injuries (n = 15; 10.4%), and neoplasms (n = 15; 10.4%). Among NFL replacement players, the leading causes of death were cardiometabolic diseases (n = 19; 51.4%), self-harm and interpersonal violence (n = 5; 13.5%), and neoplasms (n = 4; 10.8%). Among NFL football players who began their careers between 1982 and 1992, career participation in the NFL, compared with limited NFL exposure obtained primarily as an NFL replacement player during a league-wide strike, was not associated with a statistically significant difference in long-term all-cause mortality. Given the small number of events, analysis of longer periods of follow-up may be informative.

#3 Anthropometric and Athletic Performance Combine Test Results Among Positions within Grade Levels of High School-Aged American Football Players
Reference: J Strength Cond Res. 2018 Jan 30. doi: 10.1519/JSC.0000000000002481. [Epub ahead of print]
Authors: Leutzinger TJ, Gillen ZM, Miramonti AM, McKay BD, Mendez AI, Cramer JT
Summary: The purpose of the present study was to investigate differences among player positions at three grade levels in elite, collegiate-prospective American football players. Participants' data (n = 7,160) were analyzed for this study [mean height (Ht) ± standard deviation (SD) = 178 ± 7 cm, weight (Wt) = 86 ± 19 kg]. Data were obtained from 12 different high school American football recruiting combines hosted by Zybek Sports (Boulder, Colorado). Eight two-way (9x3) mixed factorial ANOVAs [position (defensive back (DB), defensive end (DE), defensive lineman (DL), linebacker (LB), offensive lineman (OL), quarterback (QB), running back (RB), tight end (TE), and wide receiver (WR) x grade (freshmen, sophomores, and juniors)] were used to test for differences among the mean test scores for each combine measure [Ht, Wt, 40-yard (40yd) dash, pro-agility drill (PA), L-cone drill (LC), vertical jump (VJ), and broad jump (BJ)]. There were position-related differences (p ≤ 0.05) for Ht, 40yd dash, and BJ, within each grade level and for Wt, PA, LC, and VJ independent of grade level. Generally, the results showed that OL were the tallest, weighed the most, and exhibited the lowest performance scores among positions. RBs were the shortest, while DBs and WRs weighed the least, and exhibited the highest performance scores among positions. These results demonstrate the value of classifying high school-aged American football players according to their specific position rather than categorical groupings such as 'line' vs. 'skill' vs. 'big skill' when evaluating anthropometric and athletic performance combine test results.

#4 Initial symptom presentation after high school football-related concussion varies by time point in a season: an initial investigation
Reference: Sports Med Open. 2018 Jan 31;4(1):8. doi: 10.1186/s40798-018-0121-8.
Authors: Brett BL, Kuhn AW, Yengo-Kahn AM, Kerr ZY, Bonfield CM, Solomon GS, Zuckerman SL
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Summary: Schedule-based and in-season factors (e.g., competition type) have been shown to be associated with symptom reporting patterns and injury severity in sport-related concussion (SRC). To determine if acute neurocognitive and symptom presentation following SRC differ by time point within a high school football season. Multicenter ambispective cohort of high school football players who sustained a SRC (N = 2594). Timing (early, mid, and late season) of SRC was based on median dates for the start of the pre-season, regular season, and playoffs of each states' football schedules. Analysis of covariance (ANCOVA) investigated differences across season period groups for: (1) neurocognitive test scores, (2) total symptom scores (TSS), and (3) individual symptom increases from baseline within 1-week post-injury. Significant group differences were observed in TSS, F(2, 2589) = 15.40, p <  0.001, ηp2 = 0.01, and individual symptom increases from baseline, F(2, 2591) = 16.40, p <  0.001, ηp2 = 0.01. Significant increases were seen from baseline to both midseason and late season in both TSS, χ2 = 24.40, p <  0.001, Φ = 0.10 and individual symptoms, χ2  = 10.32, p = 0.006, Φ = 0.10. Post hoc tests indicated a linear trend, with late-season injured athletes reporting approximately twice the TSS (13.10 vs. 6.77) and new symptoms (5.70 vs. 2.68) as those with early-season injuries. In a cohort of American high school football student-athletes, those suffering SRC in the late-season time period had increased acute symptom burden. SRC sustained later in-season may require more conservative management.

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