Latest research in football - week 3 - 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 Effects of Exercise Training under Hyperbaric Oxygen on Oxidative Stress Markers and Endurance Performance in Young Soccer Players: A Pilot Study
Reference: J Nutr Metab. 2016;2016:5647407. doi: 10.1155/2016/5647407. Epub 2016 Dec 19.
Authors: Burgos C, Henriquez-Olguin C, Andrade DC1, Ramirez-Campillo R, Araneda OF, White A, Cerda-Kohler H
Summary: The aim of the present study was to determine the effects of three weeks of hyperbaric oxygen (HBO2) training on oxidative stress markers and endurance performance in young soccer players. Participants (18.6 ± 1.6 years) were randomized into hyperbaric-hyperoxic (HH) training (n = 6) and normobaric normoxic (NN) training (n = 6) groups. Immediately before and after the 5th, 10th, and 15th training sessions, plasma oxidative stress markers (lipid hydroperoxides and uric acid), plasma antioxidant capacity (6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid [TROLOX]), arterial blood gases, acid-base balance, bases excess (BE), and blood lactate analyses were performed. Before and after intervention, maximal oxygen uptake (VO2max) and peak power output (PPO) were determined. Neither HH nor NN experienced significant changes on oxidative stress markers or antioxidant capacity during intervention. VO2max and PPO were improved (moderate effect size) after HH training. The results suggest that HBO2 endurance training does not increase oxidative stress markers and improves endurance performance in young soccer players. Our findings warrant future investigation to corroborate that HBO2 endurance training could be a potential training approach for highly competitive young soccer players.

#2 Ecologically Valid Carbohydrate Intake during Soccer-Specific Exercise Does Not Affect Running Performance in a Fed State
Reference: Nutrients. 2017 Jan 5;9(1). pii: E39. doi: 10.3390/nu9010039.
Authors: Funnell MP, Dykes NR, Owen EJ, Mears SA, Rollo I, James LJ
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Summary: This study assessed the effect of carbohydrate intake on self-selected soccer-specific running performance. Sixteen male soccer players (age 23 ± 4 years; body mass 76.9 ± 7.2 kg; predicted VO2max = 54.2 ± 2.9 mL∙kg-1∙min-1; soccer experience 13 ± 4 years) completed a progressive multistage fitness test, familiarisation trial and two experimental trials, involving a modified version of the Loughborough Intermittent Shuttle Test (LIST) to simulate a soccer match in a fed state. Subjects completed six 15 min blocks (two halves of 45 min) of intermittent shuttle running, with a 15-min half-time. Blocks 3 and 6, allowed self-selection of running speeds and sprint times, were assessed throughout. Subjects consumed 250 mL of either a 12% carbohydrate solution (CHO) or a non-caloric taste matched placebo (PLA) before and at half-time of the LIST. Sprint times were not different between trials (CHO 2.71 ± 0.15 s, PLA 2.70 ± 0.14 s; p = 0.202). Total distance covered in self-selected blocks (block 3: CHO 2.07 ± 0.06 km; PLA 2.09 ± 0.08 km; block 6: CHO 2.04 ± 0.09 km; PLA 2.06 ± 0.08 km; p = 0.122) was not different between trials. There was no difference between trials for distance covered (p ≥ 0.297) or mean speed (p ≥ 0.172) for jogging or cruising. Blood glucose concentration was greater (p < 0.001) at the end of half-time during the CHO trial. In conclusion, consumption of 250 mL of 12% CHO solution before and at half-time of a simulated soccer match does not affect self-selected running or sprint performance in a fed state.

#3 Observations of youth football training: How do coaches structure training sessions for player development?
Reference: J Sports Sci. 2017 Jan 7:1-9. doi: 10.1080/02640414.2016.1277034. [Epub ahead of print]
Authors: O'Connor D, Larkin P, Williams AM
Summary: We used systematic observation tools to explore the structure (i.e., activity and inactivity) and sequencing (i.e., the types of activities used) of football coaching sessions in Australia following the implementation of a new National Curriculum. Youth soccer coaches (n = 34), coaching within the Skill Acquisition (U11-U13 n = 19) and Game Training (U14-U17 n = 15) phases of the Football Federation Australia National Curriculum participated. Participants were filmed during a regular coaching session, with systematic observation of the session undertaken to provide a detailed analysis of the practice activities and coach behaviours. Findings indicated a session comprised of Playing Form activities (40.9%), Training Form activities (22.3%), inactivity (31%), and transitions between activities (5.8%). Coaches prescribed more Training Form activities (e.g., individual (5.4%) and drills (15.1%)) early in the session and progressed to Playing Form activities (i.e., small-sided games (15.3%) then larger games (24.8%)) later in the session. Most inactivity reflected the players listening to the coach - either in a team huddle (9.9%) or frozen on the spot during an activity (16.5%). In addition, coaches generally spent over 3 min communicating to players prior to explaining and introducing an activity regardless of when in the session the activity was scheduled.

#4 Do Neurocognitive SCAT3 Baseline Test Scores Differ Between Footballers (Soccer) Living With and Without Disability? A Cross-Sectional Study
Reference: Clin J Sport Med. 2017 Jan 17. doi: 10.1097/JSM.0000000000000407. [Epub ahead of print]
Authors: Weiler R, van Mechelen W, Fuller C, Ahmed OH, Verhagen E
Summary: The purpose was to determine if baseline Sport Concussion Assessment Tool, third Edition (SCAT3) scores differ between athletes with and without disability. Team doctors and physiotherapists supporting England football teams recorded players' SCAT 3 baseline tests from August 1, 2013 to July 31, 2014. A convenience sample of 249 England footballers, of whom 185 were players without disability (male: 119; female: 66) and 64 were players with disability (male learning disability: 17; male cerebral palsy: 28; male blind: 10; female deaf: 9). Between-group comparisons of median SCAT3 total and section scores were made using nonparametric Mann-Whitney-Wilcoxon ranked-sum test. All footballers with disability scored higher symptom severity scores compared with male players without disability. Male footballers with learning disability demonstrated no significant difference in the total number of symptoms, but recorded significantly lower scores on immediate memory and delayed recall compared with male players without disability. Male blind footballers' scored significantly higher for total concentration and delayed recall, and male footballers with cerebral palsy scored significantly higher on balance testing and immediate memory, when compared with male players without disability. Female footballers with deafness scored significantly higher for total concentration and balance testing than female footballers without disability. This study suggests that significant differences exist between SCAT3 baseline section scores for footballers with and without disability. Concussion consensus guidelines should recognize these differences and produce guidelines that are specific for the growing number of athletes living with disability.

#5 Effects of leg contrast strength training on sprint, agility and repeated change of direction performance in male soccer players
Reference: J Sports Med Phys Fitness. 2017 Jan 17. doi: 10.23736/S0022-4707.17.06951-1. [Epub ahead of print]
Authors: Hammami M, Negra Y, Shephard RJ, Souhaiel Chelly M
Summary: Contrast training is popular technique among individuals who are involved in dynamic sports, having as its goal an increase in dynamic muscular performance. It is characterized by the use of high and low loads in the same strength training session. The present investigation aimed to determine the effects of adding 8--weeks of contrast strength training (CSTP) to regular soccer practice in U--17 male soccer players during the competitive season. We hypothesized that CSTP would enhance their performance. Subjects were divided randomly divided between a control group (CG, n=12) and a contrast strength group (CSG, n=19). The 2 groups trained together; controls followed the regular soccer program, which was replaced by a contrast strength training program for the experimental group. Performance was assessed before and after training, using 10 measures : 5--10--, 20-- 30--, and 40--m sprints, a 4 x 5 m sprint (S4 x 5), a 9--3--6--3--9 m sprint with 180° turns (S180° ), a 9--3--6--3--9 m sprint with backward and forward running (SBF), a repeated--shuttle--sprint ability test (RSSA), and a repeated change of direction test (RCOD). CSG showed gains relative to controls in 5--m (p<0.000), 10--m (p<0.001), 20--m (p<0.001), 30--m (p<0.05) and 40-m (p<0.05) sprints. There were also significant gains in S180°, SBF, and S4 x 5 agility tests (p<0.01), and all RCOD parameters (p's <0.05) except RCOD--FI (p=0.055) but no significant change in any RSSA parameters. We conclude that biweekly contrast strength training can be commended to U--17 male soccer players as a means of improving many important components of athletic performance relative to standard in--season training.

#6 Agility training in young elite soccer players: promising results compared to change of direction drills
Reference: Biol Sport. 2016 Dec;33(4):345-351. doi: 10.5604/20831862.1217924. Epub 2016 Sep 10.
Authors: Chaalali A, Rouissi M, Chtara M, Owen A, Bragazzi NL, Moalla W, Chaouachi A, Amri M, Chamari K
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Summary: The aim of this study was to compare the effect of two different training programmes - change of direction (COD) vs. agility (AG) - on straight sprint (SS), COD and AG test performances in young elite soccer players. Thirty-two soccer players (age: 14.5±0.9 years; height: 171.2±5.1 cm; body mass: 56.4±7.1 kg, body fat: 10.3±2.3%) participated in a short-term (6 weeks) training study. Players were randomly assigned to two experimental groups - training with change of direction drills (COD-G, n=11) or using agility training (AG-G, n= 11) - and to a control group (CON-G, n=10). All players completed the following tests before and after training: straight sprint (15m SS), 15 m agility run with (15m-AR-B) and without a ball (15m-AR), 5-0-5 agility test, reactive agility test (RAT), and RAT test with ball (RAT-B). A significant group effect was observed for all tests (p<0.001; η2=large). In 15m SS, COD-G and AG-G improved significantly (2.21; ES=0.57 and 2.18%; ES=0.89 respectively) more than CON-G (0.59%; ES=0.14). In the 15m-AR and 5-0-5 agility test, COD-G improved significantly more (5.41%; ES=1.15 and 3.41; ES=0.55 respectively) than AG-G (3.65%; ES=1.05 and 2.24; ES=0.35 respectively) and CON-G (1.62%; ES=0.96 and 0.97; ES=0.19 respectively). Improvements in RAT and RAT-B were larger (9.37%; ES=2.28 and 7.73%; ES=2.99 respectively) in RAT-G than the other groups. In conclusion, agility performance amongst young elite soccer could be improved using COD training. Nevertheless, including a conditioning programme for agility may allow a high level of athletic performance to be achieved.

#7 Knee function among elite handball and football players 1 to 6 years after anterior cruciate ligament injury
Reference: Scand J Med Sci Sports. 2017 Jan 20. doi: 10.1111/sms.12842. [Epub ahead of print]
Authors: Myklebust G, Bahr R, Nilstad A, Steffen K
Summary: The aim of the study was to describe objective and self-reported knee function for athletes who have returned to elite handball and football play after an ACL injury, comparing these to non-injured players at the same level. A total of 414 handball and 444 football players completed baseline tests from 2007 through 2014, examining lower extremity strength, dynamic balance, knee laxity, and knee function (KOOS questionnaire). Measures were compared between injured and non-injured legs, and between injured legs and legs of controls. Eighty (9.3%) of the 858 players reported a previous ACL injury, 1 to 6 yrs post-injury (3.5±2.5 yrs), 49 handball (61.3%) and, 31 football players (38.7%). We found no difference in strength or dynamic balance between previously ACL-injured (N=80) and non-injured players legs (N=1556). However, lower quadriceps (6.3%, 95% CI: 3.2 to 9.2) and hamstrings muscle strength (6.1%, 95% CI: 3.3 to 8.1) was observed in previously ACL-injured legs compared to the non-injured contralateral side (N=80). ACL-injured knees displayed greater joint laxity than for the contralateral knee (N=80, 17%, 95% CI: 8 to 26) and healthy knees (N=1556, 23%, 95% CI: 14 to 33). KOOS scores were significantly lower for injured knees compared to knees of non-injured players. ACL-injured players who have successfully returned to elite sport have comparable strength and balance measures as their non-injured teammates. Subjective perception of knee function is strongly affected by injury history, with clinically relevant lower scores for the KOOS sub-scores Pain, Function, Sport and Quality Of Life.

#8 Non-surgical treatment of pubic overload and groin pain in amateur football players: a prospective double-blinded randomised controlled study
Reference: Knee Surg Sports Traumatol Arthrosc. 2017 Jan 16. doi: 10.1007/s00167-017-4423-z. [Epub ahead of print]
Authors: Schoberl M, Prantl L, Loose O, Zellner J, Angele P, Zeman F, Spreitzer M, Nerlich M, Krutsch W
Summary: The incidence of groin pain in athletes is steadily increasing. Symptomatic pubic overload with groin pain and aseptic osteitis pubis represent well-known and frequently misdiagnosed overuse injuries in athletes. This study investigated the benefits of standardised non-surgical treatment for swift return-to-football. In a prospective double-blinded controlled study, 143 amateur football players with groin pain as well as radiological signs and clinical symptoms of pubic overload were analysed for 1 year. Two randomised study groups participated in an intensive physical rehabilitation programme, either with or without shock wave therapy. The control group did not participate in any standardised rehabilitation programme but only stopped participating in sports activity. Follow-up examinations took place 1, 3 months and 1 year after the beginning of therapy. Endpoints were visual analogue scale (VAS), functional tests, the time of return-to-football, recurrent complaints and changes in the MR image. Forty-four football players with groin pain and aseptic osteitis pubis were randomised into two study groups; 26 received shock wave therapy, 18 did not. Clinical examination showed pubic overload as a multi-located disease. Players receiving shock wave therapy showed earlier pain relief in the VAS (p < 0.001) and returned to football significantly earlier (p = 0.048) than players without this therapy. Forty-two of 44 players of both study groups returned to football within 4 months after the beginning of therapy and had no recurrent groin pain within 1 year after trauma. Fifty-one players of the control group returned to football after 240 days (p < 0.001), of whom 26 (51%) experienced recurrent groin pain. Follow-up MRI scans did not show any effect of shock wave therapy. Non-surgical therapy is successful in treating pubic overload and osteitis pubis in athletes. Shock wave therapy as a local treatment significantly reduced pain, thus enabling return-to-football within 3 months after trauma. Early and correct diagnosis is essential for successful intensive physiotherapy.

#9 Effect of specific exercise-based football injury prevention programmes on the overall injury rate in football: a systematic review and meta-analysis of the FIFA 11 and 11+ programmes
Reference: Br J Sports Med. 2017 Jan 13. pii: bjsports-2016-097066. doi: 10.1136/bjsports-2016-097066. [Epub ahead of print]
Authors: Thorborg K, Krommes KK, Esteve E, Clausen MB, Bartels EM, Rathleff MS
Summary: The purpose was to investigate the effect of FIFA injury prevention programmes in football (FIFA 11 and FIFA 11+). Randomised controlled trials comparing the FIFA injury prevention programmes with a control (no or sham intervention) among football players. Databases such as MEDLINE via PubMed, EMBASE via OVID, CINAHL via Ebsco, Web of Science, SportDiscus and Cochrane Central Register of Controlled Trials, from 2004 to 14 March 2016 were utilized. Six cluster-randomised controlled trials had assessed the effect of FIFA injury prevention programmes compared with controls on the overall football injury incidence in recreational/subelite football. These studies included 2 specific exercise-based injury prevention programmes: FIFA 11 (2 studies) and FIFA 11+ (4 studies). The primary analysis showed a reduction in the overall injury risk ratio of 0.75 (95% CI 0.57 to 0.98), p=0.04, in favour of the FIFA injury prevention programmes. Secondary analyses revealed that when pooling the 4 studies applying the FIFA 11+ prevention programme, a reduction in the overall injury risk ratio (incidence rate ratio (IRR) 0.61; 95% CI 0.48 to 0.77, p<0.001) was present in favour of the FIFA 11+ prevention programme. No reduction was present when pooling the 2 studies including the FIFA 11 prevention programme (IRR 0.99; 95% CI 0.80 to 1.23, p=0.940). An injury-preventing effect of the FIFA injury prevention programmes compared with controls was shown in football. This effect was induced by the FIFA 11+ prevention programme which has a substantial injury-preventing effect by reducing football injuries by 39%, whereas a preventive effect of the FIFA 11 prevention programme could not be documented.

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