Latest research in football - week 45 - 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 influence of soccer playing actions on the recovery kinetics after a soccer match
Authors: Nedelec M, McCall A, Carling C, Legall F, Berthoin S, Dupont G.
Reference: J Strength Cond Res. 2013 Oct 29. [Epub ahead of print]
Summary: This study examined the relationship between the frequency of playing actions performed during a soccer match and the recovery kinetics after the match. Time motion analyses were performed on 10 professional soccer players during four competitive matches (14 observations) to determine the number of playing actions completed by players. Subjective ratings, creatine kinase and physical tests (countermovement jump, isometric maximum voluntary contraction of the hamstrings, 6-s sprint on a non-motorised treadmill) were performed before, 24 h, 48 h and 72 h after the match. During the 72-h recovery period, countermovement jump, isometric strength of the hamstring muscles and peak sprint speed significantly (p < 0.05) decreased, while muscle soreness increased (p < 0.05). Significant correlations were observed between the increase in muscle soreness and number of short sprints (< 5 m) performed at 48 h (r = 0.74, CI: 0.35 to 0.91, p < 0.01) and 72 h (r = 0.57, CI: 0.05 to 0.84, p < 0.05) following match-play. A significant relationship (r = -0.55, CI: -0.84 to -0.03, p < 0.05) was also observed between countermovement jump performance decrement at 24 h and the number of hard changes in direction performed. Soccer match play resulted in significant neuromuscular fatigue for up to 72 hours post-match and was dependent on the number of sprints and hard changes in direction performed during the match. Time motion analysis data currently used during a soccer match should quantify hard changes in direction and acceleration / deceleration phases to enable better estimations of post-match fatigue.

#2 Prediction of muscular architecture of the rectus femoris and vastus lateralis from EMG during isometric contractions in soccer players
Authors: Chauhan B, Hamzeh MA, Cuesta-Vargas AI.
Reference: Springerplus. 2013 Oct 18;2:548. doi: 10.1186/2193-1801-2-548.
Summary: The purpose of the study was to establish regression equations that could be used to predict muscle thickness and pennation angle at different intensities from electromyography (EMG) based measures of muscle activation during isometric contractions. Cross-sectional study. Simultaneous ultrasonography and EMG were used to measure pennation angle, muscle thickness and muscle activity of the rectus femoris and vastus lateralis muscles, respectively, during graded isometric knee extension contractions performed on a Cybex dynamometer. Data form fifteen male soccer players were collected in increments of approximately 25% intensity of the maximum voluntary contraction (MVC) ranging from rest to MVC. There was a significant correlation (P < 0.05) between ultrasound predictors and EMG measures for the muscle thickness of rectus femoris with an R(2) value of 0.68. There was no significant correlation (P > 0.05) between ultrasound pennation angle for the vastus lateralis predictors for EMG muscle activity with an R(2) value of 0.40. The regression equations can be used to characterise muscle thickness more accurately and to determine how it changes with contraction intensity, this provides improved estimates of muscle force when using musculoskeletal models.

#3 The Effect of Burst Duty Cycle Parameters of Medium-Frequency Alternating Current on Maximum Electrically Induced Torque of the Quadriceps Femoris, Discomfort, and Tolerated Current Amplitude in Professional Soccer Players
Reference: J Orthop Sports Phys Ther. 2013 Oct 30. [Epub ahead of print]
Authors: Liebano RE, Waszczuk S Jr, Corrêa JB.
Summary:  The primary objective was to assess the effect of the burst duty cycle parameters of medium-frequency alternating current on the maximum electrically induced torque of the quadriceps femoris. The secondary objectives were to evaluate the amount of discomfort tolerated and maximum current amplitude delivered for each electrical stimulation condition. Background Neuromuscular electrical stimulation used for muscle strengthening can improve functional performance. However, the optimal electrical stimulation parameters to be used for optimal outcomes are still unknown. Previous studies have demonstrated that the characteristics of the burst duty cycle of medium frequency alternating current influences torque generation levels and perception of sensory discomfort. Methods The maximum electrically induced torque was assessed by using a medium-frequency alternating current with a carrier frequency of 2500 Hz and a modulated frequency of 50 Hz. The current amplitude was gradually increased to the point of maximum tolerance of the participant. The testing sequence for the 3 burst duty cycles (20%, 35%, or 50%) was performed in a randomized order. Results Electrical stimulation using a 20% burst duty cycle produced an electrically induced torque greater than the 35% (P=.01) and 50% (P<.01) burst duty cycles, with no difference between 35% and 50% burst duty cycles (P=.46). There was no difference in the amount of sensory discomfort produced by the 3 duration of burst duty cycles (P=.34). There was also no difference between the 3 conditions for the maximum current amplitude tolerated (P=.62). Conclusions The burst duty cycle of 20% of medium-frequency alternating current, when compared to burst duty cycles of 35% and 50%, produced higher peak torque of the quadriceps femoris in professional soccer players. There was no difference in discomfort produced and current amplitude tolerated between the different burst duty cycle conditions.

#4 The reliability and validity of a soccer-specific non-motorized treadmill simulation
Authors: Aldous JW, Akubat I, Chrismas BC, Watkins SL, Mauger AR, Midgley AW, Abt G, Taylor L.
Reference: J Strength Cond Res. 2013 Oct 28. [Epub ahead of print]
Summary: The current study investigated the reliability and validity of a novel non-motorised treadmill (NMT) based soccer simulation utilising a novel activity category called a 'variable run' to quantify fatigue during high-speed running. Twelve male University soccer players completed three familiarisation sessions and one peak speed assessment before completing the Intermittent Soccer Performance Test (iSPT) twice. The two iSPT's were separated by 6 - 10 days. The total distance, sprint distance and high-speed running distance were 8968 ± 430 m, 980 ± 75 m and 2122 ± 140 m, respectively. No significant difference (p>0.05) was found between repeated trials of the iSPT for all physiological and performance variables. Reliability measures between iSPT1 and iSPT2 showed good agreement (CV: <4.6%; ICC: >0.80). Furthermore, the variable run phase showed high-speed running distance significantly decreased (p<0.05) in the last 15 min (89 ± 6 m) compared to the first 15 min (85 ± 7 m), quantifying decrements in high-speed exercise compared to previous literature. The current study validates the iSPT as a NMT based soccer simulation compared to previous match-play data, and is a reliable tool for assessing and monitoring physiological and performance variables in soccer players. The iSPT could be utilised in a number of ways including player rehabilitation, understanding the efficacy of nutritional interventions, and also the quantification of environmentally mediated decrements upon soccer-specific performance.

#5 Popliteus strain with concurrent deltoid ligament sprain in an elite soccer athlete: a case report
Authors: Mansfield CJ, Beaumont J, Tarnay L, Silvers H.
Reference: Int J Sports Phys Ther. 2013 Aug;8(4):452-61.
Summary: Differential diagnosis of knee pathology after trauma may be difficult when diagnosing an isolated popliteus strain and concurrent medial deltoid ligament sprain. Upon a thorough search of the published literature, the authors found no reports delineating a popliteus strain in professional soccer in the United States. The joints most affected by injury in soccer players are the knee and ankle joints. The purpose of this case report is to describe the presentation of and difficulties encountered in diagnosing a popliteus strain in a Major League Soccer athlete. During an in-season away game, an outside defender was slide-tackled from behind when his right shank was caught in an externally rotated position underneath himself and the opposing player. The initial point of contact was made to the proximal third of the posterior right shank with an anteromedially directed force. The medial longitudinal arch of the foot was forced into a more midfoot pronated position and the subtalar joint was forced into eversion. The athlete was diagnosed with a moderate strain of the right popliteus muscle with a concurrent medial deltoid ligament sprain of the right ankle. This mechanism of injury, pain with passive knee flexion and internal rotation during McMurray's test, pain with Garrick's Test and magnetic resonance imaging (MRI) study confirmed the diagnosis. The athlete returned to full ninety-minute game participation after an intensive 15-day rehabilitation program. This case is unique because the injury manifested itself at multiple joints and specifically involved the popliteus muscle. The mechanism of injury can be associated with many other soft tissue injuries to the knee, and thus, may not lead the clinician initially to consider the diagnosis of a popliteus strain. Diagnosis of this entity may be difficult due to the possible shared attachment of the popliteus muscle to the lateral meniscus, and the lack of available testing methods to assess damage to the popliteus muscle.

#6 Costing an injury prevention program in amateur adult soccer
Author: Verhagen EA.
Reference: Clin J Sport Med. 2013 Nov;23(6):500-1. doi: 10.1097/JSM.0000000000000040.
Summary: To compare the injury-related societal costs of an injury prevention program with usual warm up programs for amateur adult male soccer players. Regional amateur male soccer competitions in the Netherlands during the 2009 season were used in this study. Cost estimates in the Netherlands are made in 2009 Euros (&OV0556;1.00∼US$1.43 in late 2009). Soccer teams from 2 first-class competitions (the second-highest Dutch amateur level) were approached. Male players aged between 18 and 40 years, who were part of the first team at the start of the season, were eligible for inclusion. Twenty-three teams including 479 players were randomized and 456 (95%) were included in the analysis. The injury prevention program was The11, which includes 10 structured exercises developed by the FIFA Medical and Research Centre. The exercises, led by trained coaches, were designed to improve the stability, strength, co-ordination, and flexibility of the trunk, hip, and leg muscles and were performed 2 or 3 times per week as warm-up sessions. Compliance with the exercises was monitored randomly by the researchers. The control teams continued their usual warm-up routines. During the season, individual participants' exposure to training sessions or matches (in minutes) was reported weekly by the coaches. All participants completed questionnaires that included playing and injury history and current occupation and hours worked. Employment (vs studying) was nonsignificantly more common in the control group than the intervention group (68% vs 56%). Costs included those of the intervention, direct healthcare costs of injury, and indirect costs such as hours of work lost, which were recorded on a recovery form were used as outcome measures. Injuries occurring during the competition season were recorded weekly by the paramedical staff of the team. An injury was defined as a physical complaint sustained by a participant that resulted from a soccer training session or soccer match, whether or not there was lost time from soccer or need for medical attention. Full recovery was defined as participation throughout a training or match session. The players' injury rates were almost identical in the intervention and control groups (0.93 vs 0.94, representing 60.5% and 59.7% of players). The mean cost of The11, per player, was &OV0556;14 for the intervention group and &OV0556;0 for the control group. Direct healthcare costs per player were not significantly lower in the intervention group (difference, &OV0556;-44; 95% confidence interval [CI], -17 to 111). Indirect costs were lower in the intervention group (difference, &OV0556;-172; 95% CI, -352 to -28). The total cost per player was also lower in The11 group (difference, &OV0556;-201; 95% CI, -426 to -15). Direct health care costs per injured player were not significantly lower in the intervention group (difference, &OV0556;-76; 95% CI, -285 to 18). Indirect costs were lower in The11 group (difference, &OV0556;-288; 95% CI, -589 to -49). The total per injured player was, therefore, lower in The11 group (difference, &OV0556;-350; 95% CI, -733 to -51). The injury prevention strategy, The11, did not lower the rate of injuries in adult male soccer players, but the costs per player and per injured player were lower in the intervention group.

#7 Systematic Bias between Running Speed and Metabolic Power Data in Elite Soccer Players: Influence of Drill Type
Authors: Gaudino P, Iaia FM, Alberti G, Hawkins RD, Strudwick AJ, Gregson W.
Reference: Int J Sports Med. 2013 Oct 28. [Epub ahead of print]
Summary: The aims of the present study were to: i) evaluate the agreement between estimates of high-intensity activity during soccer small-sided games (SSGs) based on running speed alone and estimated metabolic power derived from a combination of running speed and acceleration; ii) evaluate whether any bias between the 2 approaches is dependent upon playing position or drill characteristics. 3 types of SSGs (5vs5, 7vs7 and 10vs10) were completed by 26 English Premier League outfield players. A total of 420 individual drill observations were collected over the in-season period using portable global positioning system technology. High-intensity activity was estimated using the total distance covered at speeds>14.4 km · h-1 (TS) and the equivalent metabolic power threshold of > 20 W · kg-1 (TP). We selected 0.2 as the minimally important standardised difference between methods. High-intensity demands were systematically higher (~100%, p<0.001) when expressed as TP vs. TS irrespective of playing position and SSG. The magnitude of this difference increased as the size of SSG decreased (p<0.01) with a difference of ~200% observed in the 5vs5 SSG. A greater difference between TP and TS was also evident in central defenders compared to other positions (p<0.05) particularly during the 5vs5 SSG (~350%). We conclude that the high-intensity demands of SSGs in elite soccer players are systematically underestimated by running speed alone particularly during "small" SSGs and especially for central defenders. Estimations of metabolic power provide a more valid estimation as to the true demands of SSGs.

#8 Magnetic resonance imaging as a predictor of return to play following syndesmosis (high) ankle sprains in professional football players
Authors: Howard DR, Rubin DA, Hillen TJ, Nissman DB, Lomax J, Williams T, Scott R, Cunningham B, Matava MJ.
Reference: Sports Health. 2012 Nov;4(6):535-43. doi: 10.1177/1941738112462531.

Summary: Syndesmosis ankle sprains cause greater disability and longer duration of recovery than lateral ankle sprains. To describe the severity of syndesmosis sprains using several accepted magnetic resonance imaging (MRI) criteria and to assess the interrater reliability of diagnosing syndesmosis injury using these same criteria in professional American football players. There is a high degree of interrater reliability of MRI findings in American football players with syndesmosis ankle sprains. These radiographic findings will correlate with time lost to injury, indicating severity of the sprain. Player demographics and time lost to play were recorded among professional football players who had sustained a syndesmosis ankle sprain and underwent standardized ankle MRI. Each image was independently read by 3 blinded musculoskeletal radiologists. Seventeen players met study criteria. There was almost perfect agreement among the radiologists for diagnosing injury to the syndesmotic membrane; substantial agreement for diagnosing injury to the posterior inferior tibiofibular ligament (PITFL) and in determining the proximal extent of syndesmotic edema/injury; but only fair agreement for diagnosing injury to the anterior inferior tibiofibular ligament and in determining the width of syndesmotic separation. There was a significant correlation between the width of syndesmotic separation and time lost, but no significant correlation between individual syndesmotic ligament injury or proximal extent of syndesmotic edema/injury and time lost. While ankle MRI can identify syndesmotic disruption with a high degree of interobserver agreement, no association was demonstrated between the extent of injury on MRI and the time to return to play following a high ankle sprain. In athletes with suspected high ankle sprains, MRI may help confirm diagnosis or suggest alternative diagnoses when the syndesmotic supporting structures are intact. However, the severity of ligamentous and syndesmotic disruption on MRI cannot help predict recovery times.

#9 Weight management for overweight and obese men delivered through professional football clubs: a pilot randomized trial
Authors: Gray CM, Hunt K, Mutrie N, Anderson AS, Treweek S, Wyke S.
Reference: Int J Behav Nutr Phys Act. 2013 Oct 30;10(1):121. [Epub ahead of print]
Summary: The prevalence of male obesity is increasing, but men are less likely than women to attend existing weight management programmes. We have taken a novel approach to reducing perceived barriers to weight loss for men by using professional football (soccer) clubs to encourage participation in a weight management group programme, gender-sensitised in content and style of delivery. Football Fans in Training (FFIT) provides 12 weeks of weight loss, physical activity and healthy eating advice at top professional football clubs in Scotland. This pilot randomized trial explored the feasibility of using these clubs as a setting for a randomized controlled trial of 12 month weight loss following men's participation in FFIT. A two-arm pilot trial at two Scottish Premier League football clubs (one large, one smaller), with 103 men (aged 35--65, body mass index (BMI) >=27 kg/m2) individually randomized to the intervention (n=51, received the pilot programme (p-FFIT) immediately) and waitlist comparison (n=52, received p-FFIT after four months) groups. Feasibility of recruitment, randomization, data collection and retention were assessed. Objective physical measurements (weight, waist circumference, blood pressure, body composition) and questionnaires (self-reported physical activity, diet, alcohol consumption, psychological outcomes) were obtained from both groups by fieldworkers trained to standard protocols at baseline and 12 weeks, and from the intervention group at 6 and 12 months. Qualitative methods elicited men's experiences of participation in the pilot trial. Following a short recruitment period, the recruitment target was achieved at the large, but not smaller, club. Participants' mean age was 47.1+/-8.4 years; mean BMI 34.5+/-5.0 kg/m2. Retention through the trial was good (>80% at 12 weeks and 6 months; >75% at 12 months), and 76% attended at least 80% of available programme delivery sessions. At 12 weeks, the intervention group lost significantly more weight than the comparison group (4.6% c.f. -0.6%, p<.001) and many maintained this to 12 months (intervention group baseline-12 month weight loss: 3.5%, p<.001). There were also improvements in self-reported physical activity and diet, many sustained long term. The results demonstrated the feasibility of trial procedures and the potential of FFIT to engage men in sustained weight loss and positive lifestyle change. They supported the conduct of a fully-powered randomized controlled trial.

#10 Injuries in elite youth football players: a prospective three-year study
Authors: Ergün M, Denerel HN, Binnet MS, Ertat KA.
Reference: Acta Orthop Traumatol Turc. 2013;47(5):339-46.
Summary: The aim of this study was to investigate the incidence and nature of injuries and the influence of age on injury patterns in elite youth football. Fifty-two players of the Under-17 (U-17) male national youth football team were followed during their progression to U-18 and U-19. Individual player exposure and injuries were recorded during the three year study period. Injury incidence was five times higher during matches than training. When medical attention and time loss injuries were considered, injury incidence increased during matches and decreased during training with increasing age. Traumatic injuries were more frequent in matches and were linked with increased age. Overuse injuries were two times higher during training than matches in the U-17 team. The majority of traumatic match injuries (78.3%) led to time loss and the majority of time loss injuries occurred due to traumatic mechanism (62.1%). The majority of muscle and entire ligament injuries occurred during training and contusions during competition. Re-injury rate was 25% and were all overuse injuries. Injury incidences increased during matches and decreased during training. More match injuries were caused by traumatic mechanisms as players aged. Player age might contribute to injury incidence and characteristics in youth football.

#11 Alteration of IGFBP-1 in Soccer Players Due to Intensive Training
Authors: Lagundžin D, Vučić V, Glibetić M, Nedić O.
Reference: Int J Sport Nutr Exerc Metab. 2013 Oct;23(5):449-57.
Summary: Physical activity is accompanied by the changes in Insulin-like Growth Factor I (IGF-I)/IGF-Binding Protein 1 (IGFBP-1) axis. Inconsistent results concerning IGF-I and IGFBP-1 levels were reported. In this study we have raised some questions on the events that occur at the molecular level of the exercise-related IGFBP-1 changes. We have examined the fragmentation pattern of IGFBP-1, IGFBP-1 protease activity, interaction between IGFBP-1 and alpha2-macroglobulin (α2M), and possible existence of minor structural changes of IGFBP-1 in professional soccer players. Athletes had significantly greater amounts of fragmented IGFBP-1, whereas no difference was found in the amount of intact IGFBP-1 compared with controls. An increased activity of matrix metalloprotease-9 (MMP-9) was detected in athletes, causing IGFBP-1 degradation down to the fragment of 9 kDa as the major one. The amount of α2M, which protects IGFBP-1 from proteolysis, or the amount of IGFBP-1/α2M complexes was unaltered. Finally, we have examined whether IGFBP-1 isolated from soccer players exhibited altered reactivity with several chemical surfaces used in surface-enhanced laser desorption/ionization-time of flight mass spectrometry (SELDI-TOF MS). Different reactivity was detected with anion and cation exchangers, suggesting existence of at least one sequence within IGFBP-1, whose ionization pattern was not equal in athletes and controls. Differences in spectra obtained with ion exchanges may reflect differences in IGFBP-1 phosphorylation. Physiological implications of the events described in this study on the IGF-I availability are, at this time, unknown. It can be hypothesized that IGFBP-1 proteolysis leads to altered distribution of IGF-I among IGFBPs, which may affect the final IGF-associated response.

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