Latest research in football - week 29 Part II - 2014

#1 Specific determination of maximal lactate steady state in soccer players
Reference: J Strength Cond Res. 2014 Jul 15. [Epub ahead of print]
Authors: Loures JP, Chamari K, Ferreira EC, Campos EZ, Zagatto AM, Milioni F, Sanchez da Silva AR, Papoti M.
Summary: The aim of this study was to establish the validity of the anaerobic threshold (AT) determined on the soccer specific Hoff circuit (ATHoff) in order to predict the maximal lactate steady state exercise intensity (MLSSHoff) with the ball. Sixteen soccer players (16.0±0.5 years; 63.7±9.0 kg, and 169.4±5.3 cm) were submitted to five progressive efforts (7.0 to 11.0 km·h), with ball dribbling. Thereafter, eleven players were submitted to three efforts of 30min at 100, 105, and 110% of ATHoff. The ATHoff corresponded to the speed relative to 3.5 mmol L lactate concentration. The speed relative to 4.0 mmol.L was assumed to be ATHoff4.0 and the ATHoffBI was determined through bi-segmented adjustment. For comparisons, Student t-test, intraclass correlation, and Bland & Altman analyzes were used. For reproducibility, intraclass correlation, typical error, and coefficient of variation were used. No significant difference was found between AT test and retest determined using different methods. A positive correlation was observed betweenATHoffand ATHoff4.0. The MLSSHoff (10.6±1.3 km h) was significantly different compared to ATHoff (10.2±1.2 km h) and ATHoffBI (9.5±0.4 km h) but did not show anydifference from LAnHoff4.0 (10.7±1.4 km.h). The MLSSHoff presented high intraclass correlations coefficients with ATHoffand ATHoff4.0 (ICC = 0.94; and ICC=0.89; p < 0.05, respectively), without significant correlation with ATHoffBI. The results suggest that AT determined on the Hoff circuit is reproducible and capable of predicting MLSS. The ATHoff4.0 was the method which presented a better approximation to MLSS. Therefore, it is possible to assess submaximal physiological variables through a specific circuit performed with the ball in young soccer players.


#2 Calculating the home advantage in soccer leagues
Reference: J Hum Kinet. 2014 Apr 9;40:5-6. doi: 10.2478/hukin-2014-0001. eCollection 2014.
Authors: Gómez MÁ, Pollard R
Download link: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4096081/pdf/jhk-40-05.pdf
Summary: A recent article published in the Journal of Human Kinetics (Saavedra et al., 2013) was based on a flawed methodology when calculating the home advantage values in soccer leagues. This led to incorrect calculations, false conclusions and some misleading results about home advantage in 52 soccer leagues of UEFA countries over a 10 year period. The aim of this letter was to explain these flaws and to make sure future research would not be influenced by the subsequent results and conclusions that had been presented.


#3 Physical determinants of interval sprint times in youth soccer players
Reference: J Hum Kinet. 2014 Apr 9;40:113-20. doi: 10.2478/hukin-2014-0013. eCollection 2014.
Authors: Amonette WE, Brown D, Dupler TL, Xu J, Tufano JJ, De Witt JK
Download link: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4096100/pdf/jhk-40-113.pdf
Summary: Relationships between sprinting speed, body mass, and vertical jump kinetics were assessed in 243 male soccer athletes ranging from 10-19 years. Participants ran a maximal 36.6 meter sprint; times at 9.1 (10 y) and 36.6 m (40 y) were determined using an electronic timing system. Body mass was measured by means of an electronic scale and body composition using a 3-site skinfold measurement completed by a skilled technician. Countermovement vertical jumps were performed on a force platform - from this test peak force was measured and peak power and vertical jump height were calculated. It was determined that age (r=-0.59; p<0.01), body mass (r=-0.52; p<0.01), lean mass (r=-0.61; p<0.01), vertical jump height (r=-0.67; p<0.01), peak power (r=-0.64; p<0.01), and peak force (r=-0.56; p<0.01) were correlated with time at 9.1 meters. Time-to-complete a 36.6 meter sprint was correlated with age (r=-0.71; p<0.01), body mass (r=-0.67; p<0.01), lean mass (r=-0.76; p<0.01), vertical jump height (r=-0.75; p<0.01), peak power (r=-0.78; p<0.01), and peak force (r=-0.69; p<0.01). These data indicate that soccer coaches desiring to improve speed in their athletes should devote substantive time to fitness programs that increase lean body mass and vertical force as well as power generating capabilities of their athletes. Additionally, vertical jump testing, with or without a force platform, may be a useful tool to screen soccer athletes for speed potential.


#4 Short-term performance effects of three different low-volume strength-training programmes in college male soccer players
Reference: J Hum Kinet. 2014 Apr 9;40:121-8. doi: 10.2478/hukin-2014-0014. eCollection 2014.
Authors: Brito J, Vasconcellos F, Oliveira J, Krustrup P, Rebelo A
Download link: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4096099/pdf/jhk-40-121.pdf
Summary: This study aimed to analyse the short-term performance effects of three in-season low-volume strength-training programmes in college male soccer players. Fifty-seven male college soccer players (age: 20.3±1.6 years) were randomly assigned to a resistance-training group (n=12), plyometric training group (n=12), complex training group (n=12), or a control group (n=21). In the mid-season, players underwent a 9-week strength-training programme, with two 20 min training sessions per week. Short-term effects on strength, sprint, agility, and vertical jump abilities were measured. All training groups increased 1-RM squat (range, 17.2-24.2%), plantar flexion (29.1-39.6%), and knee extension (0.5-22.2%) strength compared with the control group (p<0.05). The resistance-training group increased concentric peak torque of the knee extensor muscles by 9.9-13.7%, and changes were greater compared with the control group (p<0.05). The complex training group presented major increments (11.7%) in eccentric peak torque of the knee flexor muscles on the non-dominant limb compared with the control group and plyometric training group (p<0.05). All training groups improved 20-m sprint performance by 4.6-6.2% (p<0.001) compared with the control group. No differences were observed in 5-m sprint and agility performances (p>0.05). Overall, the results suggest that in-season low-volume strength training is adequate for developing strength and speed in soccer players.


#5 Evaluation of the Prevalence of Urinary Incontinence Symptoms in Adolescent Female Soccer Players and their Impact on Quality of Life
Reference: Occup Environ Med. 2014 Jun;71 Suppl 1:A59-60. doi: 10.1136/oemed-2014-102362.184.
Authors: Fernandes A, Fitz F, Silva A, Filoni E, Filho JM
Summary: The purpose was to evaluate the prevalence, reliability and severity of symptoms of urinary incontinence (UI) in adolescent female soccer players and the impact of those symptoms on quality of life. The present work is a cross-sectional study of 59 female adolescents divided into a group of athletes, which included 35 adolescent amateur soccer players aged between 12 and 19 years (15.6 ± 2.0), and a control group, which included 24 adolescents aged 11 to 19 years (14.8 ± 2.4) who did not practice any sports. The International Consultation on Incontinence Questionnaire - Short Form (ICIQ-SF), the pad test and King's Health Questionnaire (KHQ) were used for evaluation. The athletes displayed 62.8% positivity the pad test and the ICIQ-SF, whereas the control group exhibited 25% positivity. A medium agreement of 0.45 was found between the applied evaluation scales, as assessed with Cohen's kappa coefficient. In terms of quality of life (as assessed with the KHQ), the athletes exhibited a score of 35.2 in the General Health domain, 37.3 in the Emotions domain and 26.5 in the Sleep/Energy domain. In the present study, a high prevalence of UI symptoms was found in soccer athletes, with moderate reliability between the pad test and the ICIQ-SF; mild UI was found in both groups. The athletes had the highest scores on the General Health, Emotions and Sleep/Energy domains, which are considered to have the highest impact on quality of life.


#6 Risk and consequences of osteoarthritis after a professional football career: a systematic review of the recent literature
Reference: J Sports Med Phys Fitness. 2014 Aug;54(4):494-504.
Authors: Gouttebarge V, Inklaar H, Frings-Dresen MH.
Summary: The aim of the present study was to assess whether previous injury is a risk determinant for knee and ankle osteoarthritis (OA) in former professional football players and to explore OA-related activity and work limitations. To retrieve the relevant recent literature, the Medline, Embase and Sportdiscus databases were systematically searched for studies published from January 2000 to May 2012. Included studies must be primary studies that are written in English, Dutch, French or German and involve former professional football players; injury had to be studied as an independent variable; and knee/ankle OA, work participation or limited activities had to be described as an outcome. The data from included studies were extracted using a standardised extraction form, and the methodological quality was assessed. No studies were retrieved about injury as a risk determinant for knee/ankle OA in former professional football players. Four studies about OA-related activity and work limitations were included (three of high and one of moderate methodological quality). Up to 17% of former professional football players with knee/ankle OA reported suffering from joint pain and discomfort during activities such as squatting, walking and climbing stairs. Former professional football players with knee/ankle OA reported that their conditions were very painful, chronically painful and affected their daily lives, while 28% reported work-related limitations. Knee and ankle OA in former professional football players causes joint pain and discomfort that has negative consequences for daily life and work activities. An OA health examination programs should be developed to empower the sustainable health and functioning of professional football players.

#7 Fuzzy logic and its application in football team ranking
Reference: ScientificWorldJournal. 2014;2014:291650. doi: 10.1155/2014/291650. Epub 2014 Jun 16.
Authors: Zeng W, Li J.
Download link: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4083290/pdf/TSWJ2014-291650.pdf
Summary: Fuzzy set theory and fuzzy logic are a highly suitable and applicable basis for developing knowledge-based systems in physical education for tasks such as the selection for athletes, the evaluation for different training approaches, the team ranking, and the real-time monitoring of sports data. In this paper, we use fuzzy set theory and apply fuzzy clustering analysis in football team ranking. Based on some certain rules, we propose four parameters to calculate fuzzy similar matrix, obtain fuzzy equivalence matrix and the ranking result for our numerical example, T 7, T 3, T 1, T 9, T 10, T 8, T 11, T 12, T 2, T 6, T 5, T 4, and investigate four parameters sensitivity analysis. The study shows that our fuzzy logic method is reliable and stable when the parameters change in certain range.


#8 Suture anchor repair of proximal rectus femoris avulsions in elite football players
Reference: Knee Surg Sports Traumatol Arthrosc. 2014 Jul 17. [Epub ahead of print]
Authors: Ueblacker P, Müller-Wohlfahrt HW, Hinterwimmer S, Imhoff AB, Feucht MJ
Summary: The purpose was to report the results of suture anchor repair of proximal rectus femoris avulsions in elite football players. Four professional football players (first-team regulars of European first division football clubs) underwent suture anchor repair of complete proximal rectus femoris avulsions with significant tendon retraction. The following parameters were analysed: demographic data, mechanism of injury, type of injury, classification according to the Munich consensus statement, time between injury and surgery, time between surgery and full participation in training and availability for match and/or competition selection (return to play/RTP), and time between surgery and the comeback to the first official league match (return to competition/RTC). Radiographic evaluation was performed by magnetic resonance imaging (MRI) obtained pre-operatively and at 6 and 12 weeks post-operatively. All players were followed for at least 24 months after return to play to exclude recurrence. Mean age at surgery was 30 ± 2 years. All injuries occurred while kicking a ball, with the dominant leg affected in all patients. The injury was considered acute in three cases and chronic in one case. According to the Munich classification, all injures were type 4. Mean time to surgery was 60 ± 88 days (range, 8-191), mean time to RTP was 111 ± 15 days (range, 100-134), and mean time to RTC was 140 ± 23 days (range, 114-166). Follow-up MRIs demonstrated anatomically reinserted tendons with decreasing signal intensity over time in all cases. After a mean follow-up of 35 ± 6 months, all players were still competing at the same level as before the injury without re-injury. Suture anchor repair of proximal rectus femoris avulsions allows unrestricted return to play in professional elite football players. Return to play can be expected at approximately 16 weeks post-operatively.


#9 Profile, correlation and structure of speed in youth elite soccer players
Reference: J Hum Kinet. 2014 Apr 9;40:149-59. doi: 10.2478/hukin-2014-0017. eCollection 2014.
Authors: Tomáš M, František Z, Lucia M, Jaroslav T.
Download link: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4096104/pdf/jhk-40-149.pdf
Summary: Speed, power and agility are important components of fitness and determine the level of success and performance in soccer. The aim of this study was to identify speed variables and to determine their mutual correlation and structure in youth elite soccer players. The research group consisted of players from the Czech U16 national team (n = 22, age = 15.6 ± 0.4 years). Speed variables were assessed using the following tests: a) linear speed: 5 m sprint (S5), 10 m sprint (S10) and 20 m flying sprint (F20); b) the agility: agility test 505 with turning on the dominant (A505D) and non-dominant legs (A505N) and the K-test (K) and c) ball velocity after an instep kick with the dominant (IKD) and non-dominant (IKN) legs. Significant dependence was found for S5 compared with S10, F20 vs. A505N, K vs. A505N (p < 0.01) and S10 vs. F20 (p < 0.05). The factor analysis revealed three components of the latent variable - speed. The first component consisted of linear sprint (S10, S20) and also partially consisted of maximum speed (F20). The second component was primarily composed of agility (A505D, A505N, K) and also included maximum speed (F20). The third independent component represented ball velocity after an instep kick (IKD, IKN). The speed variables in youth elite players exhibited significant heterogeneity from the perspective of performance, as determined by the monitored tests. The structure of the speed predisposition indicated that there were three components of speed. The results of our studies support the notion that each component of speed must be considered independently when designing training programmes.