Latest research in football - week 52 - 2013

Latest research in football

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 The Effect of Carbohydrate Ingestion on Performance during a Simulated Soccer Match
Authors: Goedecke JH, White NJ, Chicktay W, Mahomed H, Durandt J, Lambert MI.
Reference: Nutrients. 2013 Dec 16;5(12):5193-204. doi: 10.3390/nu5125193.
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Summary: This study investigated how performance was affected after soccer players, in a postprandial state, ingested a 7% carbohydrate (CHO) solution compared to a placebo (0% CHO) during a simulated soccer match. Methods: Using a double-blind placebo-controlled design, 22 trained male league soccer players (age: 24 ± 7 years, wt: 73.4 ± 12.0 kg, VO2max: 51.8 ± 4.3 mL O2/kg/min) completed two trials, separated by 7 days, during which they ingested, in random order, 700 mL of either a 7% CHO or placebo drink during a simulated soccer match. Ratings of perceived exertion (RPE), agility, timed and run to fatigue were measured during the trials. Results: Change in agility times was not altered by CHO vs. placebo ingestion (0.57 ± 1.48 vs. 0.66 ± 1.00, p = 0.81). Timed runs to fatigue were 381 ± 267 s vs. 294 ± 159 s for the CHO and placebo drinks, respectively (p = 0.11). Body mass modified the relationship between time to fatigue and drink ingestion (p = 0.02 for drink × body mass), such that lower body mass was associated with increased time to fatigue when the players ingested CHO, but not placebo. RPE values for the final stage of the simulated soccer match were 8.5 ± 1.7 and 8.6 ± 1.5 for the CHO and placebo drinks respectively (p = 0.87). Conclusions: The group data showed that the 7% CHO solution (49 g CHO) did not significantly improve performance during a simulated soccer match in league soccer players who had normal pre-match nutrition. However, when adjusting for body mass, increasing CHO intake was associated with improved time to fatigue during the simulated soccer match.

#2 The incidence of knee and anterior cruciate ligament injuries over one decade in the Belgian Soccer League
Authors: Quisquater L1, Bollars P2, Vanlommel L2, Claes S2, Corten K2, Bellemans J2.
Reference: Acta Orthop Belg. 2013 Oct;79(5):541-6.
Summary: In an epidemiological study we assessed the evolution in the incidence and possible risk factors of knee injuries, especially anterior cruciate ligament (ACL) injuries, in Belgian soccer over one decade. Two soccer seasons (1999-2000 and 2009-2010) were compared and 56,364 injury reports registered by the KBVB-URBSFA were retrieved. Knee injuries totaled 9.971 cases, 5.495 in the first season (1999-2000) and 4.476 in the second (2009-2010): a significant decrease in incidence from 1.5 per 100 players in 2000 to 1.2 knee injuries in 2010. Six percent of all knee injuries were ACL injuries. The reported incidence of ACL tears slightly increased from 0.081 to 0.084 per 100 players. Female gender, competition and age over 18 years were prognosticators for ACL injuries. Enhanced prevention programs for ACL injuries, especially in those sports groups are warranted.

#3 Soccer Injuries and Recovery In Dutch Male Amateur Soccer Players: Results of a Prospective Cohort Study
Authors: van Beijsterveldt AM, Steffen K, Stubbe JH, Frederiks JE, van de Port IG, Backx FJ.
Reference: Clin J Sport Med. 2013 Dec 16. [Epub ahead of print]
Summary: To describe characteristics of outdoor soccer injury and recovery among Dutch soccer players. The 2009-2010 competitive season (33 weeks) and 456 Dutch male soccer players of 23 amateur teams participated in this study.  Coaches recorded individual exposure to all soccer activities. Paramedics or sports trainers collected information on the occurrence (eg, location, type, circumstances) and consequences (eg, absenteeism, medical treatment) of injuries. In total, 424 time-loss injuries were sustained by 60% (n = 274) of the players, with 23% (n = 105) having more than 1 injury. This corresponds to an overall density of 9.6 (8.7-10.5) injuries per 1000 player hours; 3.9 (3.3-4.7) in training sessions and 20.4 (18.1-23.1) in soccer matches. Almost 30% (n = 123) of the injuries lasted for more than 1 month, 14% (n = 58) were re-injuries (causing longer absence than new injuries), and 54% (n = 230) of the injuries were given medical treatment. The most common diagnoses were muscle/tendon (38%) or joint/ligament injuries (23%) of the lower extremities. After regaining the ability to fully take part in soccer training or matches, 27.4% of the players (n = 116) still reported complaints. Two recommendations based on the above-mentioned results are (1) prevention should primarily focus on these most common diagnoses and (2) players resuming soccer activities after an injury should be given special attention to resolve the remaining complaints and to prevent re-injuries.

#4 Aerobic Fitness Ecological Validity in Elite Soccer Players: a Metabolic-Power Approach
Authors: Vincenzo M, Franco I, Carlo C.
Reference: J Strength Cond Res. 2013 Dec 17. [Epub ahead of print]
Summary: The aim of this study was to examine the association between match metabolic power (MP) categories and aerobic-fitness in elite-level male soccer players. Seventeen male professional soccer players were tested for VO2max, maximal aerobic speed (MAS), VO2 at ventilatory threshold (VO2VT and % VO2VT) and speed at a selected blood-lactate concentration (4 mmol· l, VL4). Aerobic-fitness tests were performed at end of pre-season and after 12 and 24 weeks during the championship. Aerobic fitness and MP variables were considered as mean of all seasonal testing and of 16 Championship home matches for all the calculations, respectively. Results showed that VO2max (from 0.55 to 0.68), MAS (from 0.52 to 0.72), VO2VT (from 0.72 to 0.83), %VO2VT (from 0.62 to 0.65) and VL4 (from 0.56 to 0.73) were significantly (p< 0.05 to 0.001) large to very large associated with MP variables. These results provide evidence to the ecological validity of aerobic-fitness in male professional-soccer. Strength and conditioning professionals should consider aerobic-fitness in their training program when dealing with professional male soccer players. The MP method resulted an interesting approach for tracking external-load in male professional soccer-players.

#5 Optimal Recovery Time for Postactivation Potentiation in Professional Soccer Players
Authors: Mola J, Bruce-Low S, Burnet S.
Reference: J Strength Cond Res. 2013 Dec 13. [Epub ahead of print]
Summary: Resistance exercise may acutely enhance muscle contractile activity which is known as postactivation potentiation (PAP). PAP augments important skills that require power production that are necessary during soccer performance. The aim of this study was to determine the optimal recovery time to elicit PAP following a bout of high-intensity resistance exercise in professional soccer players. Twenty-two senior professional soccer players [Mean(SD): age, 23(4.5) y; stature, 1.83(6.6) m; body mass, 80.9(7.8) kg] were randomised to either an experimental (n=11) or a control group (n=11). Both groups performed a standardised warm-up and baseline countermovement jump (CMJ) followed by a 10 min recovery. The control group then performed a CMJ at 15 s and at 4, 8, 12, 16 and 20 min, whereas the experimental group performed a 3RM squat and then an identical CMJ protocol. No significant differences were found between groups for CMJ peak-power (p >0.05) or jump height (p >0.05). No time effect for peak-power (F(6,60)=2.448; p=.063) or jump-height (F(6,60)=2.399; p=.089) was observed throughout the experimental group trials. Responders (n=6) displayed individualised PAP profiles at 4 (n=3), 12 (n=1) and 16 (n=2) min post conditioning contraction whereas non-responders (n=5) did not. A set of 3RM squats failed to acutely potentiate all participants CMJ performance. Both PAP responders and non-responders were identified and have individualised PAP time-constants. This is not consistent with previous literature which used identical protocols. Strength and conditioning practitioners need to individualise recovery 'windows' and identify athletes who respond to PAP prior to undertaking a complex-training intervention.

#6 The preventive effect of the Nordic hamstring exercise on hamstring injuries in amateur soccer players: study protocol for a randomised controlled trial
Authors: van der Horst N, Smits DW, Petersen J, Goedhart EA, Backx FJ.
Reference: Inj Prev. 2013 Dec 13. doi: 10.1136/injuryprev-2013-041092. [Epub ahead of print]
Summary: Hamstring injuries are the most common muscle injury in male amateur soccer players and have a high rate of recurrence, often despite extensive treatment and long rehabilitation periods. Eccentric strength and flexibility are recognised as important modifiable risk factors, which have led to the development of eccentric hamstring exercises, such as the Nordic hamstring exercise. As the effectiveness of the Nordic hamstring exercise in reducing hamstring injuries has never been investigated in amateur soccer players, the aim of this study is to investigate the effect of this exercise on the incidence and severity of hamstring injuries in male amateur soccer players. An additional aim is to determine whether flexibility is associated with hamstring injuries.  Dutch male amateur soccer players, aged 18-40 years, were allocated to an intervention or control group. Both study groups continued regular soccer training during 2013, but the intervention group additionally performed the Nordic hamstring exercise (25 sessions over 13 weeks). Primary outcomes are the incidence of initial and recurrent hamstring injury and injury severity. Secondary outcomes are hamstring-and-lower-back flexibility and compliance. Compliance to the intervention protocol was also monitored. Eccentric hamstring strength exercises are hypothesised to reduce the incidence of hamstring injury among male amateur soccer players by 70%. The prevention of such injuries will be beneficial to soccer players, clubs, football associations, health insurance companies and society.

#7 The Diagnostic and Prognostic Value of Ultrasonography in Soccer Players With Acute Hamstring Injuries
Authors: Petersen J, Thorborg K, Nielsen MB, Skjødt T, Bolvig L, Bang N, Hölmich P.
Reference: Am J Sports Med. 2013 Dec 11. [Epub ahead of print]
Summary: An injury to the hamstring muscle complex is the most common injury in soccer. Ultrasound of acute hamstring injuries is often used as a clinical tool for diagnosing hamstring injuries and guiding players in when they can return to play. The aim of the study were to (1) investigate the characteristic sonographic findings of acute hamstring injuries in soccer players, (2) compare the mean injury severity (time to return to play) in injured players with and without sonographically verified abnormalities, and (3) correlate the length of the injured area and absence from soccer play (time to return to play) to investigate if ultrasonography can be used as a prognostic indicator of time to return to play. Players from 50 teams participating in 1 of the top 5 Danish soccer divisions were followed in the period from January to December 2008. Of 67 players with acute hamstring injuries, 51 underwent ultrasonographic examination of the injured thigh and were included in this study. Ultrasonographic examinations were performed 1 to 10 days after injury (mean, 5.2 ± 3.0 days), and sonographic findings were present in 31 of 51 cases (61%). Two thirds of the injuries were to the biceps femoris muscle and one third to the semitendinosus muscle. No total ruptures were documented. The 51 acute hamstring injuries resulted in absence from soccer of a mean 25.4 ± 15.7 days per injury, with no significant difference between players with and without sonographically verified abnormalities (P = .41). No correlation existed between the length of the injured area and injury severity (r = 0.19, P = .29). The biceps femoris is the most commonly injured hamstring muscle detected by ultrasound, and more than half of the injuries are intramuscular. Because neither the presence of sonographic findings nor the size of the findings was correlated with time to return to play in injured soccer players, the prognosis of hamstring injuries should not be guided by these findings alone.

#8 Effects of recreational soccer in men with prostate cancer undergoing androgen deprivation therapy: study protocol for the 'FC Prostate' randomized controlled trial
Authors: Uth J, Schmidt JF, Christensen JF, Hornstrup T, Andersen LJ, Hansen PR, Christensen KB, Andersen LL, Helge EW, Brasso K, Rørth M, Krustrup P, Midtgaard J.
Reference: BMC Cancer. 2013 Dec 13;13:595. doi: 10.1186/1471-2407-13-595.
Summary: Androgen deprivation therapy (ADT) is a cornerstone in the treatment of advanced prostate cancer. Adverse musculoskeletal and cardiovascular effects of ADT are widely reported and investigations into the potential of exercise to ameliorate the effects of treatment are warranted. The 'Football Club (FC) Prostate' study is a randomized trial comparing the effects of soccer training with standard treatment approaches on body composition, cardiovascular function, physical function parameters, glucose tolerance, bone health, and patient-reported outcomes in men undergoing ADT for prostate cancer. Using a single-center randomized controlled design, 80 men with histologically confirmed locally advanced or disseminated prostate cancer undergoing ADT for 6 months or more at The Copenhagen University Hospital will be enrolled on this trial. After baseline assessments eligible participants will be randomly assigned to a soccer training group or a control group receiving usual care. The soccer intervention will consist of 12 weeks of training 2-3 times/week for 45-60 min after which the assessment protocol will be repeated. Soccer training will then continue bi-weekly for an additional 20 weeks at the end of which all measures will be repeated to allow for additional analyses of long-term effects. The primary endpoint is changes in lean body mass from baseline to 12 weeks assessed by dual X-ray absorptiometry scan. Secondary endpoints include changes of cardiovascular, metabolic, and physical function parameters, as well as markers of bone metabolism and patient-reported outcomes. The FC Prostate trial will assess the safety and efficacy of a novel soccer-training approach to cancer rehabilitation on a number of clinically important health outcomes in men with advanced prostate cancer during ADT. The results may pave the way for innovative, community-based interventions in the approach to treating prostate cancer.

#9 The impact of single nucleotide polymorphisms on patterns of non-contact musculoskeletal soft tissue injuries in a football player population according to ethnicity
Authors: Pruna R1, Ribas J2, Montoro JB3, Artells R4.
Reference: Med Clin (Barc). 2013 Dec 13. pii: S0025-7753(13)00735-5. doi: 10.1016/j.medcli.2013.09.026. [Epub ahead of print]
Summary: The prevention, diagnosis, and management of non-contact musculoskeletal soft tissue injuries (NCMSTIs) related to participation in sports are key components of sport and exercise medicine. Epidemiological data have demonstrated the existence of interindividual differences in the severity of NCMSTIs, indicating that these injuries occur as a consequence of both extrinsic and intrinsic factors, including genetic variations. We have collected data on NCMSTIs suffered by 73 elite players of White, black African and Hispanic ethnicity of European football over the course of three consecutive seasons. We have also examined eight single nucleotide polymorphisms (SNPs) in genes related to tissue recovery and tissue repair in blood drawn from the players and correlated our findings with type and severity of injuries in each ethnic group. The frequency of the SNPs varied among the three ethnic sub-groups (p<0.0001). Among Whites, a significant relationship was observed between ligament injuries and ELN (p=0.001) and between tendinous injuries and ELN (p=0.05) and IGF2 (p=0.05). Among Hispanics, there was a significant relation between muscle injuries and ELN (p=0.032) and IGF2 (p=0.016). Interracial genotypic differences may be important in the study of NCMSTIs. A genetic profile based on SNPs may be useful tool to describe each individual's injuribility risk and provide specific treatment and preventive care for football players.


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