Latest research in football - week 42 - 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 Repeated-Sprint Ability in Division I Collegiate Male Soccer Players: Positional Differences and Relationships with Performance Tests
Reference: J Strength Cond Res. 2017 Oct 16. doi: 10.1519/JSC.0000000000001948. [Epub ahead of print]
Autors: Lockie RG, Moreno MR, Orjalo AJ, Stage AA, Liu TM, Birmingham-Babauta SA, Hurley JM, Torne IA, Beiley MD, Risso FG, Davis DL, Lazar A, Stokes JJ, Giuliano DV.
Summary: Repeated-sprint ability (RSA) in essential for soccer. Important considerations when assessing RSA is whether there are differences between positions (defenders, midfielders, forwards), and what physiological characteristics may contribute to RSA. This has not been assessed in collegiate male players. Eighteen Division I male field players from one school performed several performance tests. The RSA test involved 7 x 30-m sprints completed on 20-s cycles. Measurements included total time (TT), and performance decrement (percent change in time from the first to last sprint; PD). Subjects also completed tests of lower-body power (vertical [VJ] and standing broad [SBJ] jump); linear (30-m sprint; 0-5, 0-10, 0-30 m intervals) and change-of-direction (505) speed; and soccer-specific endurance (Yo-Yo Intermittent Recovery Test Level 2; YYIRT2). A one-way ANOVA (p < 0.05) determined between-position differences, and effect sizes were calculated. Pearson's correlations (p < 0.05) calculated relationships between RSA TT and PD with the other tests. There were no significant between-position differences for any test. There were large effects for the faster right-leg 505 and greater YYIRT2 distance for midfielders compared to defenders and forwards. Nonetheless, no between-position differences in RSA TT and PD were documented. There were relationships between RSA TT and the VJ (r = -0.59), SBJ (r = -0.61), 0-10 m (r = 0.64) and 0-30 m (r = 0.83) sprint intervals. There were no significant correlations for RSA PD. Male field players from one collegiate soccer team can demonstrate similar RSA across different positions. Greater lower-body power and sprinting speed could augment RSA.

#2 Pre-season dietary intake of professional soccer players
Reference: Nutr Health. 2017 Jan 1:260106017737014. doi: 10.1177/0260106017737014. [Epub ahead of print]
Authors: Raizel R, Godois ADM, Coqueiro AY, Voltarelli FA, Fett CA, Tirapegui J, Ravagnani FCP, Coelho-Ravagnani CF
Summary: Despite the well-documented importance of nutrition in optimizing performance and health, the dietary intake of soccer players has attracted little attention. We aimed to assess the pre-season dietary intake of professional soccer players and its adequacy in macro and micronutrients. The pre-season dietary intake of 19 male athletes was assessed using a semi-structured 3-day food record. To determine dietary adequacy and excess, energy and macronutrient intake were compared with the Brazilian dietary reference values for athletes, and micronutrients were compared with the Estimated Average Requirement - EAR (minimum recommendation) and Tolerable Upper Intake Level - UL (maximum recommendation). Mean daily energy intake (40.74±12.81 kcal/kg) was adequate. However, there was a low carbohydrate intake (5.44±1.86 g/kg/day) and a high amount of protein and fat (1.91±0.75 and 1.27±0.50 g/kg/day, respectively). Sodium intake (3141.77±939.76 mg/day) was higher than UL (2300 mg/day), while the majority of players showed daily intake of vitamin A (74%), vitamin D (100%), folate (58%), calcium and magnesium (68%) below the EAR (625, 10 and 320 µg/day, 800 and 330 mg/day, respectively). The dietary intake of professional soccer players was adequate in energy, but inadequate in macro and micronutrients, which suggests the need to improve nutritional practices to sustain the physical demands of soccer during pre-season.

#3 Head and neck size and neck strength predict linear and rotational acceleration during purposeful soccer heading
Reference: Sports Biomech. 2017 Oct 16:1-15. doi: 10.1080/14763141.2017.1360385. [Epub ahead of print]
Authors: Caccese JB, Buckley TA, Tierney RT, Arbogast KB, Rose WC, Glutting JJ, Kaminski TW
Summary: There is increasing societal concern about the long-term effects of repeated impacts from soccer heading, but there is little information about ways to reduce head impact severity. The purpose of this study was to identify factors that contribute to head acceleration during soccer heading. One-hundred soccer players completed 12 controlled soccer headers. Peak linear (PLA) and rotational (PRA) accelerations were measured using a triaxial accelerometer and gyroscope. Head acceleration contributing factors were grouped into 3 categories: size (head mass, neck girth), strength (sternocleidomastoid, upper trapezius) and technique [kinematics (trunk, head-to-trunk range-of-motion), sternocleidomastoid and upper trapezius activity]. Multiple regression analyses indicated size variables explained 22.1% of the variance in PLA and 23.3% of the variance in PRA; strength variables explained 13.3% of the variance in PLA and 17.2% of the variance in PRA; technique variables did not significantly predict PLA or PRA. These findings suggest that head and neck size and neck strength predict PLA and PRA. Anthropometric and neck strength measurements should be considered when determining an athlete's readiness to begin soccer heading.

#4 Difference in kick motion of adolescent soccer players in presence and absence of low back pain
Reference: Gait Posture. 2017 Oct 7;59:89-92. doi: 10.1016/j.gaitpost.2017.10.012. [Epub ahead of print]
Authors: Tojima M, Torii S
Summary: Many adolescent soccer players experience low back pain (LBP). However, there are no reports studying the kick motion of adolescent soccer players experiencing LBP. This study aimed to clarify the kick motion of adolescent soccer players in the presence and absence of LBP. We recruited 42 adolescent soccer players and divided them into two groups according to the presence of LBP (LBP group, n=22) and absence of LBP (NBP group, n=20). We measured real-time kick motion using a three-dimensional motion analysis system. We placed 65 spherical markers on each anatomical landmark and calculated the angle of the lumbar spine, center of mass (COM) of the whole body, and displacement of the support foot. We used an unpaired t-test to compare the data between the groups. Compared with the NBP group, the LBP group showed a lateral shift in COM, which increased the duration of kick motion. The presence of LBP affected the posterior positioning of the support foot and restricted the player's lumbar spine from bending laterally. A lateral shift in COM and larger rotation of the lumbar spine could stress the lumbar spine during kick motion. Therefore, coaches and athletic trainers should pay attention to soccer players' lumbar spine rotation and the COM shift during kick motion. This would be important for preventing LBP in adolescent soccer players.

#5 Hamstring muscle injuries in elite football: translating research into practice
Reference: Br J Sports Med. 2017 Oct 19. pii: bjsports-2017-097573. doi: 10.1136/bjsports-2017-097573. [Epub ahead of print]
Authors: Buckthorpe M, Gimpel M, Wright S, Sturdy T, Stride M

#6 A social network analysis of the goal scoring passing networks of the 2016 European Football Championships
Reference: Hum Mov Sci. 2017 Oct 16. pii: S0167-9457(17)30539-0. doi: 10.1016/j.humov.2017.10.001. [Epub ahead of print]
Authors: Mclean S, Salmon PM, Gorman AD, Stevens NJ, Solomon C
Summary: In the current study, social network analysis (SNA) and notational analysis (NA) methods were applied to examine the goal scoring passing networks (GSPN) for all goals scored at the 2016 European Football Championships. The aim of the study was to determine the GSPN characteristics for the overall tournament, between the group and knock out stages, and for the successful and unsuccessful teams. The study also used degree centrality (DC) metrics as a novel method to determine the relative contributions of the pitch locations involved in the GSPN. To determine changes in GSPN characteristics as a function of changing score line, the analysis considered the match status of the game when goals were scored. There were significant differences for SNA metrics as a function of match status, and for the DC metrics in the comparison of the different pitch locations. There were no differences in the SNA metrics for the GSPN between teams in the group and knock out stages, or between the successful and unsuccessful teams. The results indicate that the GSPN had low values for network density, cohesion, connections, and duration. The networks were direct in terms of pitch zones utilised, where 85% of the GSPN included passes that were played within zones or progressed through the zones towards the goal. SNA and NA metrics were significantly different as a function of changing match status. The current study adds to the previous research on goal scoring in football, and demonstrates a novel method to determine the prominent pitch zones involved in the GSPN. These results have implications for match analysis and the coaching process.

#7 "Football is a boys' game": children's perceptions about barriers for physical activity during recess time
Reference: Int J Qual Stud Health Well-being. 2017;12(sup2):1379338. doi: 10.1080/17482631.2017.1379338.
Authors: Martinez-Andres M, Bartolome-Gutierrez R, Rodriguez-Martin B, Pardo-Guijarro MJ, Martinez-Vizcaino V
Summary: The aim of the study was to know the factors that influence boys and girls' perceptions for performing physical activity during playground recess from their own perspective. Ninety-eight schoolchildren aged 8-11 years from five schools from Cuenca (Spain) participated in 22 focus groups and carried out 98 drawings following the socioecological model as a theoretical framework. A content analysis of the transcripts from the focus groups and drawings was carried out by three researchers. Results showed that, in spite of boys and girls identified same barriers, there were gender differences in their perceptions. Gender socialization was the key as central category and helped to understand these differences. Boys preferred play football and this sport had a monopoly on the recess space. Weather was a barrier for boys. Girls and boys, who did not play football, were relegated to peripheral areas and lack of materials was a barrier for them. Teachers were a barrier for all children who did not play football. Thus, in order to promote recess physical activity, researchers, teachers and educational policy makers should take into account gender socialization and promote inclusive non-curricular physical activity in schools.

#8 Effectiveness of above real-time training on decision-making in elite football: A dose-response investigation
Reference: Prog Brain Res. 2017;234:101-116. doi: 10.1016/bs.pbr.2017.08.007. Epub 2017 Sep 22.
Authors: Farahani JJ, Javadi AH, O'Neill BV, Walsh V
Summary: We examined the effects of video-based training in elite footballers' decision-making by presenting videos with training and testing scenarios at above real-time speeds. We also examined different training protocols to establish how much training is beneficial. We found that above real-time training improved accuracy and response time in football decision-making. In terms of scheduling, we found that the benefits were short lasting and did not last beyond 2 weeks.

#9 Elite professional soccer players’ experience of injury prevention
Reference: Cogent Medicine
Authors: Kristiansen JB, Larsson I.
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Summary: Injuries are common in professional soccer and might interfere with the ability of the team and the individual player to perform. Several studies have shown the benefits of exercise as a means to prevent injuries in soccer, but research is needed to substantiate, how injury prevention strategies are best implemented. The purpose of this study was to describe and interpret soccer players’ experience of injury prevention. A hermeneutic phenomenological approach was used as described by van Manen. Eight professional Danish soccer players were interviewed with open-ended interviews. The players’ lived experience of injury prevention across all the interviews were shown as the interaction between three overreaching themes: (1) being a part of a performance environment, (2) the need for an individual approach and (3) strong personal ambitions. Interaction between the three themes empowered the players to engage in injury prevention. Professional soccer players’ experience of injury prevention can be interpreted within the four components of the empowerment model: (1) impact, (2) competence, (3) meaningfulness and (4) choice. The presence of the four components empowered the players to engage in injury prevention in the soccer club.

Australian Football
#1 SCAT3 changes from baseline and associations with X2 Patch measured head acceleration in amateur Australian football players
Reference: J Sci Med Sport. 2017 Oct 6. pii: S1440-2440(17)31637-7. doi: 10.1016/j.jsams.2017.09.591. [Epub ahead of print]
Authors: Willmott C, McIntosh AS, Howard T, Mitra B, Dimech-Betancourt B, Donovan J, Rosenfeld JV
Summary: The purpose was to investigate changes from baseline on SCAT3 as a result of football game exposure, and association with X2 Patch measured head acceleration events in amateur Australian footballers. Peak linear acceleration (PLA) of the head (>10 g) was measured by wearable head acceleration sensor X2 Biosystems X-Patch in male (n=34) and female (n=19) Australian footballers. SCAT3 was administered at baseline (B) and post-game (PG). 1394 head acceleration events (HEA) >10 g were measured. Mean and median HEA PLA were recorded as 15.2 g (SD=9.2, range=10.0-115.8) and 12.4 g (IQR=11.0-15.6) respectively. No significant difference in median HEA PLA (g) was detected across gender (p=0.55), however, more HEAs were recorded in males (p=0.03). A greater number (p=0.004) and severity (p<0.001) of symptoms were reported PG than at B. No significant association between number of HEA or median PLA, and SCAT3 change scores (p>0.05 for all), was identified for either gender. Increase in symptom severity post game was not associated with X2 measured HEA. Males sustained more HEA, however HEA PLA magnitude did not differ across gender. Further work on the validation of head acceleration sensors is required and their role in sports concussion research and medical management.

#2 The Influence of Physical Qualities on Activity Profiles of Female Australian Football Match-Play
Reference: Int J Sports Physiol Perform. 2017 Oct 16:1-20. doi: 10.1123/ijspp.2016-0723. [Epub ahead of print]
Authors: Black GM, Gabbett TJ, Johnston RD, Cole MH, Naughton G, Dawson B
Summary: The rapid transition of female Australian football players from amateur to semi-elite competitions has the potential for athletes to be underprepared for match-play. To gain an understanding the match demands of female football, the aims of this study were three-fold: (1) to highlight the physical qualities that discriminate selected and non-selected female Australian Football players, (2) to investigate activity profiles of female Australian Football players, and (3) to gain an understanding of the influence of physical qualities on running performance in female Australian Football match-play. Twenty-two female Australian football (AF) state academy players (mean ± SD age, 23.2 ± 4.5 years) and 27 non-selected players (mean ± SD age, 23.4 ± 4.9 years) participated in this study. The Yo-Yo Intermittent Recovery Test (Level 1), countermovement jump and 30m sprint tests were completed prior to the competitive season. During 14 matches, players wore global positioning system (GPS) units to describe the running demands of female AF match-play. Selected players were faster over 30 metres (ES=0.57; p=0.04) and covered greater distances on the Yo-Yo IR1 test (ES=1.09; p<0.001). Selected midfielders spent greater time on the field and covered greater total distances (ES=0.73-0.85; p<0.009). No differences were reported in relative distances covered between selected and non-selected players (p=0.08). Players who were faster over 5 metres (r= -0.612), and 30-metres (r= -0.807) and performed better on the Yo-Yo IR1 (r=0.489) covered greater high-speed distances during match-play. Selected female AF players were faster and had greater intermittent running ability than players not selected to a State academy program. An emphasis should be placed on the development of physical fitness in this playing group to ensure optimal preparation for the national competition.

American football
#1 High-magnitude head impact exposure in youth football
Reference: J Neurosurg Pediatr. 2017 Oct 17:1-9. doi: 10.3171/2017.5.PEDS17185. [Epub ahead of print]
Authors: Campolettano ET, Gellner RA, Rowson S
Summary: Even in the absence of a clinically diagnosed concussion, research suggests that neurocognitive changes may develop in football players as a result of frequent head impacts that occur during football games and practices. The objectives of this study were to determine the specific situations in which high-magnitude impacts (accelerations exceeding 40 g) occur in youth football games and practices and to assess how representative practice activities are of games with regard to high-magnitude head impact exposure. METHODS A total of 45 players (mean age 10.7 ± 1.1 years) on 2 youth teams (Juniors [mean age 9.9 ± 0.6 years; mean body mass 38.9 ± 9.9 kg] and Seniors [mean age 11.9 ± 0.6 years; mean body mass 51.4 ± 11.8 kg]) wore helmets instrumented with accelerometer arrays to record head impact accelerations for all practices and games. Video recordings from practices and games were used to verify all high-magnitude head impacts, identify specific impact characteristics, and determine the amount of time spent in each activity. RESULTS A total of 7590 impacts were recorded, of which 571 resulted in high-magnitude head impact accelerations exceeding 40 g (8%). Impacts were characterized based on the position played by the team member who received the impact, the part of the field where the impact occurred, whether the impact occurred during a game or practice play, and the cause of the impact. High-magnitude impacts occurred most frequently in the open field in both games (59.4%) and practices (67.5%). "Back" position players experienced a greater proportion of high-magnitude head impacts than players at other positions. The 2 teams in this study structured their practice sessions similarly with respect to time spent in each drill, but impact rates differed for each drill between the teams. CONCLUSIONS High-magnitude head impact exposure in games and practice drills was quantified and used as the basis for comparison of exposure in the 2 settings. In this cohort, game impact rates exceeded those for practice. Back players, who were often positioned in the open field, were shown to experience elevated levels of head impact exposure relative to players at other positions. The analysis also suggests that practice intensity, which may be influenced by coaching style, may also affect high-magnitude head impact exposure. Future studies should investigate this aspect as a factor affecting head impact exposure.

#2 Examination of Risk for Sleep Disordered Breathing among College Football Players
Reference: J Sport Rehabil. 2017 Oct 16:1-24. doi: 10.1123/jsr.2017-0127. [Epub ahead of print]
Authors: Peck B, Renzi T, Peach H, Gaultney J, Marino JS
Summary: Professional football linemen are at risk for sleep disordered breathing (SDB) compared to other types of athletes. It is currently unknown whether collegiate football linemen display a similar risk profile. The objectives were 1) Determine for the first time whether collegiate football linemen show risk for SDB, and 2) Test the hypothesis that SDB risk is higher in collegiate football linemen compared to an athletic comparison group. Male football linemen (n = 21) and track (n = 22) Division I athletes between the ages of 18 and 22 participated in this study.  Participants completed the Multivariable Apnea Prediction (MAP) Index and Epworth Sleepiness Scale (ESS) surveys, validated measures of symptoms of sleep apnea and daytime sleepiness, respectively. Neck and waist circumferences, blood pressure, Mallampati Index (MMPI) and Tonsil Size were determined, followed by body composition assessment using DEXA. Scores from surveys, anthropometric data, MMPI and body composition were used in the statistical analysis. Survey data demonstrated a deficiency in sleep quality and efficiency, coinciding with increased self-reported symptoms of apnea (MAP index=0.79) in college linemen relative to track athletes. Neck circumference (45cm), waist circumference (107.07cm), body mass index (36.64kg/m2) and body fat % (30.19%), all of which exceeded the clinical predictors of risk for obstructive sleep apnea, were significantly greater in linemen compared to track athletes. MAP variables were significantly correlated with MMPI, neck circumference, body fat %, body mass index, and systolic blood pressure (r ≥ .31, p < 0.05), indicating that college football linemen are at increased risk for SDB. Risk factors for SDB recognized in professional football linemen are also present at the collegiate level. Screening may minimize present or future risk for SDB, as well as the downstream risk of SDB-associated metabolic and cardiovascular disease.

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