Latest research in football - week 47 - 2014

 As previous literature updates, we 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 Field Test Performances between Elite and Sub-Elite Academy Soccer Players
Reference:  J Athl Enhancement 3:4 doi:10.4172/2324-9080.1000158 (2014)
Authors: Stewart A, Bloom L, Clarkson B, Comfort P
Summary: The findings of this study highlight that there are no significant differences (p>0.05) in the height (175.1 ± 5.4 cm vs. 171.8 ± 5.8 cm) and body mass (69.5 ± 6.9 kg vs. 68.1 ± 5.8 kg) of Elite and Sub- Elite squads respectively. In contrast the Elite squad demonstrated significant quicker sprint performances in the 5 m (0.98 ± 0.05 s vs. 1.02 ± 0.06 s; p=0.01) and 20 m (2.95 ± 0.09 s vs. 3.06 ± 0.15 s; p=0.003) sprints, higher SJ (51.8 ± 3.9 cm vs. 37.8 ± 3.8 cm; p<0.001) and CMJ (55.1 ± 4.5 cm vs. 38.6 ± 3.9 cm; p<0.001) performance and significantly greater relative strength (2.14 ± 0.25 kg/kg vs. 1.81 ± 0.34 kg/kg, p<0.001) compared to the Sub-elite squad, respectively. Results suggest that strength, jump and sprint tests can all differentiate between elite and sub-elite youth soccer players, highlighting the importance of appropriate conditioning to develop strength and power in youth soccer players.

#2 The Contribution of Youth Sport Football to Weekend Physical Activity for Males Aged 9- to 16- Years: Variability Related to Age and Playing Position
Reference: Pediatr Exerc Sci. 2014 Nov 10. [Epub ahead of print]
Authors: Fenton S AM, Duda JL, Barrett T.
Summary: The aims of this study were (1) to determine minutes of moderate-to-vigorous physical activity (MVPA) and vigorous physical activity (VPA) accrued in youth sport football (also internationally referred to as soccer), and the contribution towards daily weekend MVPA and VPA for males aged 9 to 16 years, and (2) to investigate variability in these outcomes related to age and playing position. One hundred and nine male grassroots footballers (Mean age = 11.98 ± 1.75 years) wore a GT3X accelerometer for 7 days. Weekend youth sport football participation and playing position were recorded. Youth sport football MVPA (M = 51.51 ± 17.99) and VPA (M = 27.78 ± 14.55) contributed 60.27% and 70.68% towards daily weekend MVPA and VPA, respectively. Overall, 36.70% of participants accumulated ≥ 60 minutes MVPA and 69.70% accrued ≥ 20 minutes of VPA during youth sport. For participants aged 13 to16 years, youth sport football MVPA and VPA were significantly higher, and contributed a greater amount towards daily weekend MVPA and VPA than for participants aged 9 to 12 years (p = <.01). Youth sport football is an important source of MVPA and VPA at the weekend for male youth, and particularly for adolescents. Participation may offer opportunity for weekend engagement in VPA towards health enhancing levels.

#3 Biceps femoris and semitendinosus-teammates or competitors? New insights into hamstring injury mechanisms in male football players: a muscle functional MRI study
Reference: Br J Sports Med. 2014 Dec;48(22):1599-606. doi: 10.1136/bjsports-2014-094017.
Authors: Schuermans J, Van Tiggelen D, Danneels L, Witvrouw E
Summary: The hamstring injury mechanism was assessed by investigating the exercise-related metabolic activity characteristics of the hamstring muscles using a muscle functional MRI (mfMRI) protocol. 27 healthy male football players and 27 football players with a history of hamstring injuries (recovered and playing fully) underwent standardised mfMR Imaging. The mfMRI protocol consisted of a resting scan, a strenuous bilateral eccentric hamstring exercise and a postexercise scan. The exercise-related T2 increase or the signal intensity shift between both scans was used to detect differences in metabolic activation characteristics (1) between the different hamstring muscle bellies and (2) between the injury group and the control group. A more symmetrical muscle recruitment pattern corresponding to a less economic hamstring muscle activation was demonstrated in the formerly injured group (p<0.05). The injured group also demonstrated a significantly lower strength endurance capacity during the eccentric hamstring exercise. These findings suggest that the vulnerability of the hamstring muscles to football-related injury is related to the complexity and close coherence in the synergistic muscle recruitment of the biceps femoris and the semitendinosus. Discrete differences in neuromuscular coordination and activity distribution, with the biceps femoris partly having to compensate for the lack of endurance capacity of the semitendinosus, probably increase the hamstring injury risk.

#4 Seasonal Training Load Quantification in Elite English Premier League Soccer Players
Reference: Int J Sports Physiol Perform. 2014 Nov 13. [Epub ahead of print]
Authors: Malone JJ, Di Michele R, Morgans R, Burgess D, Morton JP, Drust B.
Summary: The purpose was to quantify the seasonal training load completed by professional soccer players of the English Premier League. Thirty players were sampled (using GPS, heart rate and RPE) during the daily training sessions comprising the 2011-2012 pre-season and in-season period. Pre-season data were analysed across 6 x 1 week microcycles. In-season data were analysed across 6 x 6 week mesocycle blocks and 3 x 1 week microcycles at start, mid and end time points. Data were also analysed with respect to number of days prior to a match. Typical daily training load (i.e. total distance, high speed distance, % HRmax, s-RPE) did not differ during each week of the pre-season phase. However, daily total distance covered was 1304 (95% CI: 434 - 2174) m greater in the first mesocycle compared with the sixth. %HRmax values were also greater (3.3 (1.3 - 5.4) %) in the third mesocycle compared with the first. Furthermore, training load was lower on the day before match (MD-1) compared with two (MD-2) to five (MD-5) days before match, though no difference was apparent between these latter time-points. We provide the first report of seasonal training load in elite soccer players and observed periodization of training load was typically confined to MD-1 (regardless of mesocycle) whereas no differences were apparent during MD-2 to MD-5. Future studies should evaluate whether this loading and periodization is facilitative of optimal training adaptations and match day performance.

#5 Effects of Regular Away Travel on Training Loads, Recovery and Injury Rates in Professional Australian Soccer Players
Reference: Int J Sports Physiol Perform. 2014 Nov 13. [Epub ahead of print]
Authors: Fowler P, Duffield R, Waterson A, Vaile J.
Summary: The present study examined the acute and longitudinal effects of regular away travel on training loads (TL), player wellness and injury surrounding competitive soccer (football) matches. Eighteen male professional football players, representing a team competing in the highest national competition in Australia, volunteered to participate in the study. Training loads, player wellness and injury incidence, rate, severity and type, together with the activity at the time of injury were recorded on the day prior to, the day of and for four days following each of the 27 matches of the 2012/2013 season. This included 14 home and 13 away matches, further subdivided based on the mid-point of the season into early (1-13) and late competition (14-27) phases. Whilst TL were significantly greater on day 3 at home compared to away during the early competition phase (p=0.03), no other significant effects of match location were identified (p>0.05). Total TL and mean wellness over the six days surrounding matches, and TL on day 3 were significantly reduced during the late compared to the early competition phase at home and away (p<0.05). Though not significant (p>0.05), training missed due to injury was 60 and 50 % greater during the late compared to the early competition phase at home and away, respectively. In conclusion, no significant interactions between match location and competition phase were evident during the late competition phase, which suggests away travel had negligible cumulative effects on the reduction in player wellness in the latter half of the season.

#6 Not quite so fast: effect of training at 90% sprint speed on maximal and repeated-sprint ability in soccer players
Reference: J Sports Sci. 2014 Nov 11:1-8. [Epub ahead of print]
Authors: Haugen T, Tonnessen E, Leirstein S, Hem E, Seiler S.
Summary: The aim of the present study was to investigate the effect of training at an intensity eliciting 90% of maximal sprinting speed on maximal and repeated-sprint performance in soccer. It was hypothesised that sprint training at 90% of maximal velocity would improve soccer-related sprinting. Twenty-two junior club-level male and female soccer players (age 17 ± 1 year, body mass 64 ± 8 kg, body height 174 ± 8 cm) completed an intervention study where the training group (TG) replaced one of their weekly soccer training sessions with a repeated-sprint training session performed at 90% of maximal sprint speed, while the control group (CG) completed regular soccer training according to their teams' original training plans. Countermovement jump, 12 × 20-m repeated-sprint, VO2max and the Yo-Yo Intermittent Recovery Level 1 test were performed prior to and after a 9-week intervention period. No significant between-group differences were observed for any of the performance indices and effect magnitudes were trivial or small. Before rejecting the hypothesis, we recommend that future studies should perform intervention programmes with either stronger stimulus or at other times during the season where total training load is reduced.

#7 The management of sportsman's groin hernia in professional and amateur soccer players: a revised concept
Reference: Hernia. 2014 Nov 8. [Epub ahead of print]
Authors: Kopelman D, Kaplan U, Hatoum OA, Abaya N, Karni D, Berber A, Sharon P, Peskin B.
Summary: Chronic groin pain appears in athletes with a diverse etiology. In a select few, it can be defined as a sportsman's hernia, that may be related, among other pathologies, to weakness of the posterior inguinal wall and may successfully respond to surgery. Surgical repair of the sportsman's hernia is associated with good functional outcomes, if the diagnosis is based on meticulous examination and follows a simple selection flowchart. The study assessed patients recruited from 2006 until the present assessed by a dedicated team with clinical and radiographic features of a sportsman's hernia who had failed a specified period of conservative therapies. Surgery was performed using a tension-free mesh open inguinal hernia repair. Of 246 male patients with chronic groin pain, 51 underwent surgery (mean age 20.7 years, range 14-36 years) with 58 inguinal procedures performed. Of the operated group, seven underwent bilateral surgery with a direct hernia found in 9/58 operated sides (15.5 %), an indirect hernial sac in 8/58 (14 %) and a direct and indirect hernia being found in 3/58 (5 %) of operated sides. There was no post-operative morbidity (median follow-up 36.1 months; range 1-74 months), with two failures (3.45 % of operated sides). All other patients were asymptomatic, returned to full sports activity within 4.3 weeks (range 3-8 weeks) after surgery, and required no analgesics or further treatment. Selective surgical hernia repair, based on meticulous anamnesis and physical examination is effective in the management of chronic groin pain in athletes.

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