Latest research in football - week 51 - 2015

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 Jump Rope Training: Balance and Motor Coordination in Preadolescent Soccer Players
Reference: J Sports Sci Med. 2015 Nov 24;14(4):792-8. eCollection 2015.
Authors: Trecroci A, Cavaggioni L, Caccia R, Alberti G
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Summary: General physical practice and multidimensional exercises are essential elements that allow young athletes to enhance their coordinative traits, balance, and strength and power levels, which are linked to the learning soccer-specific skills. Jumping rope is a widely-used and non-specific practical method for the development of athletic conditioning, balance and coordination in several disciplines. Thus, the aim of this study was to investigate the effects of a short-term training protocol including jumping rope (JR) exercises on motor abilities and body balance in young soccer players. Twenty-four preadolescent soccer players were recruited and placed in two different groups. In the Experimental group (EG), children performed JR training at the beginning of the training session. The control group (CG), executed soccer specific drills. Harre circuit test (HCT) and Lower Quarter Y balance test (YBT-LQ) were selected to evaluate participant's motor ability (e.g. ability to perform rapidly a course with different physical tasks such as somersault and passages above/below obstacles ) and to assess unilateral dynamic lower limb balance after 8 weeks of training. Statistical analysis consisted of paired t-test and mixed analysis of variance scores to determine any significant interactions. Children who performed jumping rope exercises showed a significant decrease of 9% (p < 0.01, ES = 0.50-0.80) in the performance time of HCT. With regard to the CG, no differences were highlighted (p > 0.05, ES = 0.05-0.2) from pre- to post-training. A training-by-group interaction was found for the composite score in both legs (p < 0.05, Part η(2) > 0.14). Our findings demonstrated that JR practice within regular soccer training enhanced general motor coordination and balance in preadolescent soccer players. Therefore, the inclusion of JR practice within regular soccer training session should encouraged to improve children's motor skills. Key pointsPerforming jumping rope exercises within a regular soccer program can be an additional method to improve balance and motor coordination.The performance improvement in the Harre Circuit Test associated with jump rope training can potentially be attributed to an enhancement of the inter-limb coordination and SSC ability.Results from the present study indicate that young soccer players should be encouraged to practice general physical activities together with sport-specific exercise during their training sessions.

#2 Effects of in-season uphill sprinting on physical characteristics in semi-professional soccer players
Reference: J Sports Med Phys Fitness. 2015 Dec 3. [Epub ahead of print]
Authors: Kavaliauskas M, Kilvington R, Babraj J
Summary: Soccer performance is determined by a number of physiological adaptations that can be altered by high intensity training. However, the effectiveness of using an uphill sprint based protocol has not been demonstrated for soccer players. We sought to determine the effectiveness of an in-season uphill sprint training (UST) programme on soccer related physiological outcomes. 14 male soccer players (age: 22 ± 8 years, height: 1.81 ± 8 m, body mass: 76 ± 12 kg) underwent testing (5-10-5 agility drill, Yo-Yo Intermittent Recovery Test Level 1, leg and back dynamometry & 3km time trial) at baseline and after 6 weeks of UST or normal activity. Participants were allocated to a control (n=7) or UST (n=7) group. The UST group took part in twice weekly training consisting of 10 x 10 sec sprints with 60s recovery on a 7% gradient for 6 weeks. The control group maintained normal activity patterns. 3km time trial, strength, agility and Yo-Yo performance were all significantly improved pre to post following 6 weeks of UST (Agility 3%, d=1.3; Strength 10%, d=-3.2; VO2 max 3%, d=-1.4; 3-km TT 4%, d=1.3). In the control group 3km time trial, strength, agility and Yo-Yo performance remained unchanged after 6 weeks (Agility 0.1%, d=-0.2; Strength 2%, d=0.0; VO2 max -0.1%, d=0.0; 3-km TT 1.3%, d=0.3). Therefore in-season short duration UST is an effective way to improve soccer fitness in a time efficient manner.

#3 Preseason preparation training and endothelial function in elite professional soccer players
Reference: Vasc Health Risk Manag. 2015 Nov 26;11:595-9. doi: 10.2147/VHRM.S92636. eCollection 2015.
Authors: Androulakis NE, Koundourakis NE, Nioti E, Spatharaki P, Hatzisymeon D, Miminas I, Alexandrakis MG
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Summary: The purpose was to examine whether a high volume of soccer-specific training can lead to endothelial activation and/or dysfunction in professional soccer players due to exercise-induced oxidative stress. Twenty-three (15 nonsmokers and eight smokers) healthy, elite male professional soccer players (mean age: 25.2±4.3 years, BMI: 23.1±1.3 kg/m(2), fat: 7.8%±2.6%) were selected for this study. All participants had a full clinical and laboratory evaluation. von Willebrand factor antigen (vWf Ag) plasma levels were measured on two different occasions: 1 day before the beginning of the preseason preparation period and after 7 weeks of strenuous exercise. Mean vWf Ag plasma levels were significantly decreased from 95.1%±26% to 88.3%±27.2% at the end of the experimental period (P=0.018), suggesting a potential beneficial effect on the endothelium of these athletes. Further analysis showed that age greater than 29 years with an age range from 29 to 34 years can not impair this effect (P>0.05). Strenuous exercise did not lead to endothelium activation or dysfunction in well-trained elite soccer players. On the contrary, it seemed to produce a beneficial effect on the endothelium of these players.

#4 Soccer Injuries in Players Aged 7 to 12 Years: A Descriptive Epidemiological Study Over 2 Seasons
Reference: Am J Sports Med. 2015 Dec 8. pii: 0363546515614816. [Epub ahead of print]
Authors: Rössler R, Junge A, Chomiak J, Dvorak J, Faude O
Summary: As part of a risk-management approach, sound epidemiological data are needed to develop prevention programs. A recent review on soccer injuries of players younger than 19 years concluded that prospective data concerning children are lacking. The purpose was to analyze the incidence and characteristics of soccer injuries in children aged 7 to 12 years. The present survey was a prospective descriptive epidemiological study on soccer injuries over 2 seasons in the Czech Republic and Switzerland. Exposure of players during training and match play (in hours) and injury data were reported by coaches via an Internet-based registration system. Location, type, and severity of injuries were classified according to an established consensus. Injury characteristics are presented as absolute numbers and injury incidence rates (injuries per 1000 hours of soccer exposure). An injury was defined as any physical complaint sustained during a scheduled training session or match play resulting in at least 1 of the following: (1) inability to complete the current match or training session, (2) absence from subsequent training sessions or matches, and (3) injury requiring medical attention. In total, 6038 player-seasons with 395,295 hours of soccer exposure were recorded. The mean (±SD) age of the players was 9.5 ± 2.0 years, and 3.9% of the participants were girls. A total of 417 injuries were reported. Most (76.3%) injuries were located in the lower limbs, with 15.6% located in the upper limbs. Joint and ligament injuries comprised 30.5%, contusions 22.5%, muscle and tendon injuries 18.5%, and fractures and bone injuries 15.4% of all injuries; 23.7% of injuries led to more than 28 days of absence from sport participation. The overall injury incidence was 0.61 (95% CI, 0.53-0.69) injuries per 1000 hours of soccer exposure during training sessions and 4.57 (95% CI, 4.00-5.23) during match play. Injury incidence rates increased with increasing age. The observed injury incidences were lower compared with studies in youth players. Children showed a relatively high proportion of fractures and bone stress and of injuries to the upper limbs. The study provides an evidence base for injury incidence rates and injury characteristics in children's soccer. These data are the basis to develop an age-specific injury-prevention program.

#5 Rates and Determinants of Return to Play After Anterior Cruciate Ligament Reconstruction in National Collegiate Athletic Association Division I Soccer
Reference: Am J Sports Med. 2015 Dec 4. pii: 0363546515614315. [Epub ahead of print]
Authors: Howard JS, Lembach ML, Metzler AV, Johnson DL
Summary: Factors and details regarding return to play in elite, collegiate female soccer athletes after an anterior cruciate ligament (ACL) injury and reconstruction have not been well studied. The purpose was to evaluate return to play among collegiate female soccer players, specifically examining the effect of surgical and individual athlete characteristics on the return-to-play rate. Sports medicine and athletic training staff at institutions from the National Collegiate Athletic Association Southeastern Conference (SEC) were contacted to request participation in the study. All institutions were sent a standardized spreadsheet with response choices and instructions regarding athlete inclusion criteria. Athlete, injury, surgical technique, and return-to-play data were requested for ACL reconstructions performed on female soccer athletes at the participating institutions over the previous 8 years. χ2 analyses were used to compare the return-to-play rate by year in school, scholarship status, position, depth chart status, procedure, graft type, graft fixation, concomitant procedures, and previous ACL injuries. All 14 of the SEC institutions chose to participate and provided data. A total of 80 ACL injuries were reported, with 79 surgical reconstructions and return-to-play data for 78 collegiate soccer athletes. The overall return-to-play rate was 85%. There was a statistical significance in return-to-play rates favoring athletes in earlier years of eligibility versus later years (P < .001). Athletes in eligibility years 4 and 5 combined had a return-to-play rate of only 40%. Scholarship status likewise showed significance (P < .001), demonstrating a higher return-to-play rate for scholarship athletes (91%) versus nonscholarship athletes (46%). No significant differences in return-to-play rates were observed based on surgical factors, including concomitant knee procedures, graft type, and graft fixation method. Collegiate female soccer athletes have a high initial return-to-play rate. Undergoing ACL reconstruction earlier in the college career as well as the presence of a scholarship had a positive effect on return to play. Surgical factors including graft type, fixation method, tunnel placement technique, concomitant knee surgeries, and revision status demonstrated no significant effect on the return-to-play rate.

#6 Return to Training and Playing After Acute Lisfranc Injuries in Elite Professional Soccer and Rugby Players
Reference: Am J Sports Med. 2015 Dec 4. pii: 0363546515616814. [Epub ahead of print]
Authors: Deol RS, Roche A, Calder JD
Summary: Joint injuries are increasingly recognized in elite soccer and rugby players. Currently, no evidence-based guidelines exist on time frames for return to training and competition after surgical treatment. The purpose of the study was to assess the time to return to training and playing after Lisfranc joint injuries. A consecutive series of 17 professional soccer and rugby players in the English Premier/Championship leagues was assessed using prospectively collected data. All were isolated injuries sustained during training or competitive matches. Each player had clinical and radiological evidence of an unstable Lisfranc injury and required surgical treatment. A standardized postoperative regimen was used. The minimum follow-up time was 2 years. Clinical and radiological follow-up was obtained in all 17 players. Seven players had primarily ligamentous injuries, and 10 had bony injuries. The time from injury to fixation ranged from 8 to 31 days, and hardware was removed at 16 weeks postoperatively. One athlete retired after a ligamentous injury; the remaining 16 players returned to training and full competition. Excluding the retired player, the mean time to return to training was 20.1 weeks (range, 18-24 weeks) and to full competition was 25.3 weeks (range, 21-31 weeks). There was a significant difference between the mean time to return to competition for rugby (27.8 weeks) and soccer players (24.1 weeks; P = .02) and for ligamentous (22.5 weeks) compared with bony injuries (26.9 weeks; P = .003). Three patients suffered deep peroneal nerve sensation loss, from which 1 patient did not fully recover. Return to competitive elite-level soccer and rugby is possible after surgically treated Lisfranc injuries. Return to training can take up to 24 weeks and return to playing up to 31 weeks, with bony injuries taking longer.

#7 Short biceps femoris fascicles and eccentric knee flexor weakness increase the risk of hamstring injury in elite football (soccer): a prospective cohort study
Reference: Br J Sports Med. 2015 Dec 16. pii: bjsports-2015-095362. doi: 10.1136/bjsports-2015-095362. [Epub ahead of print]
Authors: Timmins RG, Bourne MN, Shield AJ, Williams MD, Lorenzen C, Opar DA
Summary: The purpose was to investigate the role of eccentric knee flexor strength, between-limb imbalance and biceps femoris long head (BFlh) fascicle length on the risk of future hamstring strain injury (HSI). Elite soccer players (n=152) from eight different teams participated. Eccentric knee flexor strength during the Nordic hamstring exercise and BFlh fascicle length were assessed at the beginning of preseason. The occurrences of HSIs following this were recorded by the team medical staff. Relative risk (RR) was determined for univariate data, and logistic regression was employed for multivariate data. Twenty seven new HSIs were reported. Eccentric knee flexor strength below 337 N (RR=4.4; 95% CI 1.1 to 17.5) and possessing BFlh fascicles shorter than 10.56 cm (RR=4.1; 95% CI 1.9 to 8.7) significantly increased the risk of a HSI. Multivariate logistic regression revealed significant effects when combinations of age, history of HSI, eccentric knee flexor strength and BFlh fascicle length were explored. From these analyses the likelihood of a future HSI in older athletes or those with a HSI history was reduced if high levels of eccentric knee flexor strength and longer BFlh fascicles were present. The presence of short BFlh fascicles and low levels of eccentric knee flexor strength in elite soccer players increases the risk of future HSI. The greater risk of a future HSI in older players or those with a previous HSI is reduced when they have longer BFlh fascicles and high levels of eccentric strength.

#8 Muscle Activation and Performance During Trunk Strength Testing in High-Level Female and Male Football Players
Reference: J Appl Biomech. 2015 Dec 14. [Epub ahead of print]
Authors: Roth R, Donath L, Zahner L, Faude O
Summary: For performance and injury prevention in sports core strength and endurance are focused prerequisites. Therefore we evaluated characteristics of trunk muscle activation and performance during strength-endurance related trunk field tests. Strength-endurance ability, as total time to failure, and activation of trunk muscles was measured in 39 football players of the highest German women's soccer league (Bundesliga) (N=18, age, 20.7 (SD 4.4) y) and the highest national male under-19 league (N=21, age, 17.9 (0.7) y) in prone plank, side plank and dorsal position. Maximal isometric force was assessed during trunk extension and flexion, rotation and lateral flexion in order to normalize EMG and to compare to the results of strength-endurance tests. For all positions of endurance strength tests a continuous increase in normalized EMG activation was observed (p<0.001). Muscle activation of mm. rectus abdominis and external oblique in prone plank position exceeded the maximal voluntary isometric contraction activation, with a significantly higher activation in females (p=0.02). We conclude, that in the applied strength-endurance testing, the activation of trunk muscles was high, especially in women. As high trunk muscle activation can infer fatigue, limb strength can limit performance in prone and side plank position particularly during high trunk muscle activation.

#9 Complete tear of the distal hamstring tendons in a professional football player: a case report and review of the literature
Reference: Skeletal Radiol. 2015 Dec 14. [Epub ahead of print]
Authors: Aldebeyan S, Boily M, Martineau PA
Summary: Semimembranosus tendon ruptures are rare and are often associated with involvement of the cruciate ligaments. We present a 24-year-old American football player who sustained a complete rupture of the semimembranosus tendon near its insertion associated with an avulsion fracture of the conjoint attachment of the lateral collateral ligament (LCL) and biceps femoris with intact cruciate ligaments and menisci during practice. At the scene he was immobilized and was taken to the hospital immediately. The diagnosis was reached after radiographs and an MRI of the affected knee were obtained. The semimembranosus tendon and the avulsion of the biceps femoris insertion were repaired surgically. We also review the literature for previously reported cases of distal hamstring injuries.

#10 Informational constraints on interceptive actions of elite football goalkeepers in 1v1 dyads during competitive performance
Reference: J Sports Sci. 2015 Dec 14:1-6. [Epub ahead of print]
Authors: Shafizadeh M, Davids K, Correia V, Wheat J, Hizan H
Summary: The aim of this study was to examine whether perceptual variables can provide informational constraints for the goalkeepers to intercept the ball successfully in 1v1 dyads. Video images of 42 actions (1v1 in direct shots) were selected randomly from different matches and divided into conceded goals (n = 20) and saved actions (n = 22) to investigate interceptive actions of 20 goalkeepers in the English Premier League in season 2013-2014. Time to Contact (TTC) of the closing distance gap between shooter and goalkeeper was obtained by digitising actions in the 18-yard penalty box. Statistical analyses revealed that, in sequences of play resulting in an intercepted shot at goal, goalkeepers closed down outfield players in the X axis, whereas when a goal was conceded, there was a significantly delayed movement by goalkeepers toward the shooters in this plane. The results of canonical correlations showed that a decreasing distance between a shooter and goalkeeper, and accompanied reduction in relative interpersonal velocity followed a temporal pattern. Findings of this study showed how perception of key informational constraints on dyadic system relations, such as TTC, interpersonal distance and relative velocity, constrain elite goalkeepers' interceptive actions, playing an important role in successful performance.

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