Latest research in football - week 21 - 2014

#1 Rating of muscular and respiratory perceived exertion in professional soccer players
Reference: J Strength Cond Res. 2014 May 19. [Epub ahead of print]
Authors: Los Arcos A, Yanci J, Mendiguchia J, Gorostiaga EM.
Summary: This study investigated, in male professional players: 1) fluctuations in rating of local-muscular (sRPEmus) and central-respiratory (sRPEres) perceived exertion measured after the completion of each training and competitive session, over a 9 week competitive period, and 2) the influence of quantitative assessment of different training and competition modes on changes in physical performance. sRPEres, sRPEmus and heart rate (HR) were measured in 21 players in 847 individual training and competitive sessions. Training load (TL) was calculated by multiplying sRPEmus or sRPEres by the duration of the training or competition sessions. A test battery (vertical jump, sprint and endurance running) was performed before and after the studied period. At the end of official matches average sRPEmus was higher (7.4±0.6, p<0.05) than sRPEres (6.4±1.3). Significant negative correlations were observed between the values of total training and competition time (r=-0.62, p<0.01) or total added sRPEmus (r =-0.59, p<0.05), and vertical jump or sprint running velocity changes, respectively. This suggests that sRPEmus should be considered the main fatigue rating during a soccer match. Training and competition volume may have negative effects on the muscle power performance gains of the legs.


#2 The reliability and validity of the Carminatti’s test for aerobic fitness in youth soccer players
Reference: J Strength Cond Res. 2014 May 19. [Epub ahead of print]
Authors: Teixeira AS, Fernandes da Silva J, Carminatti LJ, Dittrich N, Castagna C, Antonacci Guglielmo LG.
Summary: In this study, we examined the reliability and validity of peak velocity determined using the Carminatti's test (PVT-CAR) to evaluate the aerobic fitness of young soccer players (age 13.4 ± 1.2 years; range 10.3 to 15.4 years). To determine test-retest reliability of PVT-CAR, 34 adolescents (U-12, n=13; U-14, n=21) performed the Carminatti's test twice within 3-5 days. Validity was assessed in 43 adolescents (U-14, n=20; U-16, n=23) submitted to both the Carminatti's test and an incremental treadmill test to determine their aerobic fitness indicators. The intraclass correlation of PVT-CAR was 0.89, 0.93 and 0.81 with a coefficient of variation of 2.30% (0.33 kmh), 1.89% (0.26 kmh) and 2.66% (0.39 kmh) for the total sample (pooled data) or separately for the U-12 and U-14 groups, respectively. No significant difference was found between PVT-CAR and maximal aerobic speed (MAS) for the total sample (pooled data) or separately for the U-14 and U-16 groups. In addition, Bland and Altman plots evidenced acceptable agreement between them. The PVT-CAR was significantly related with peak velocity and MAS obtained in the incremental test for the total sample (r= 0.86 and 0.81, p<0.01, respectively) and separately for the U-14 (r= 0.84 and 0.75, p<0.01, respectively) and U-16 groups (r= 0.60 and 0.58, p<0.01, respectively). Furthermore, the PVT-CAR was correlated with the VO2peak (r=0.57, p<0.01) and the velocity associated to the second ventilatory threshold (r=0.69, p<0.01) when the data were pooled (total sample). As a result, the Carminatti's test may be considered as a reliable and valid measure for assessing and monitoring the development of MAS of young soccer players during adolescence.


#3 Implementation of a neuromuscular training programme in female adolescent football: 3-year follow-up study after a randomised controlled trial
Reference: Br J Sports Med. 2014 May 21. pii: bjsports-2013-093298. doi: 10.1136/bjsports-2013-093298. [Epub ahead of print]
Authors: Lindblom H, Waldén M, Carlfjord S, Hägglund M.
Summary: Neuromuscular training (NMT) has been shown to reduce anterior cruciate ligament injury rates in highly structured clinical trials. However, there is a paucity of studies that evaluate implementation of NMT programmes in sports. The purpose of this study was to evaluate the implementation of an NMT programme in female adolescent football 3 years after a randomised controlled trial (RCT). Cross-sectional follow-up after an RCT using the Reach, Effectiveness, Adoption, Implementation, and Maintenance Sports Setting Matrix (RE-AIM SSM) framework. Questionnaires were sent to the Swedish Football Association (FA), to eight district FAs and coaches (n=303) that participated in the RCT in 2009, and coaches who did not participate in the RCT but were coaching female adolescent football teams during the 2012 season (n=496). Response rates were 100% among the FAs, 57% among trial coaches and 36% among currently active coaches. The reach of the intervention was high, 99% of trial coaches (control group) and 91% of current coaches were familiar with the programme. The adoption rate was 74% among current coaches, but programme modifications were common among coaches. No district FA had formal policies regarding implementation, and 87% of current coaches reported no club routines for programme use. Maintenance was fairly high; 82% of trial coaches from the intervention group and 68% from the control group still used the programme. Reach and adoption of the programme was high among coaches. However, this study identified low programme fidelity and lack of formal policies for its implementation and use in clubs and district FAs.


#4 Predicting the lateral direction of deceptive and non-deceptive penalty kicks in football from the kinematics of the kicker
Reference: Hum Mov Sci. 2014 May 17. pii: S0167-9457(14)00060-8. doi: 10.1016/j.humov.2014.04.004. [Epub ahead of print]
Authors: Lopes JE, Jacobs DM, Travieso D, Araújo D.
Summary: This study addresses the utility of the kinematics of penalty takers for goalkeepers in association football. Twelve professional and semi-professional players shot to one side of the goal with (deceptive condition) or without (non-deceptive condition) simulating a shot to the opposite side. The body kinematics of the penalty takers were registered with motion-capture apparatus. Correlation and regression techniques were used to determine the relation between the shot direction and aspects of the penalty taker's kinematics at different moments. Several kinematic variables were strongly correlated with shot direction, especially those related to the lower part of the body. Some of these variables, including the angle of the non-kicking foot, acquired high correlations at time intervals that are useful to goalkeepers. Compound variables, here defined as linear combinations of variables, were found to be more useful than locally defined variables. Whereas some kinematic variables showed substantial differences in their relation to ball direction depending on deception, other kinematic variables were less affected by deception. Results are interpreted with the hypothesis of non-substitutability of genuine action. The study can also be interpreted as extending the correlation and regression methodology, often used to analyze variables defined at single moments, to the analysis of variables in a time continuous fashion.


#5 Low back pain in female elite football and handball players compared with an active control group
Reference: Knee Surg Sports Traumatol Arthrosc. 2014 May 18. [Epub ahead of print]
Authors: Tunås P, Nilstad A, Myklebust G.
Summary: The purpose of this cross-sectional study was to compare the prevalence of low back pain (LBP) among female elite football and handball players to a matched non-professional active control group. The participants were requested to answer a questionnaire based on standardized Nordic questionnaires for musculoskeletal symptoms to assess the prevalence of LBP. Included participants were elite female football (n = 277) and handball players (n = 190), and a randomly selected control group from the Norwegian population (n = 167). Fifty-seven percentage of the football players, 59 % of the handball players and 60 % of the control group had experienced LBP the previous year. There were no significant group differences in the prevalence of LBP ever (p = 0.62), the previous year (p = 0.85) or the previous 7 days (p = 0.63). For both sports, there was a significant increase in prevalence of LBP from the resting period to the competitive periods of the season (p ≤ 0.001). Seventy percent of the goalkeepers in both football and handball had experienced LBP the previous year. There were no difference in LBP among female elite football and handball players compared with the control group. However, female elite athletes in football and handball reported a high prevalence of LBP compared to previous studies. The variations in LBP and playing positions indicate that specific field positions, in football and handball, is a risk factor for developing LBP.


#6 Risk factors, testing and preventative strategies for non-contact injuries in professional football: current perceptions and practices of 44 teams from various premier leagues
Reference: Br J Sports Med. 2014 May 16. pii: bjsports-2014-093439. doi: 10.1136/bjsports-2014-093439. [Epub ahead of print]
Authors: McCall A, Carling C, Nedelec M, Davison M, Le Gall F, Berthoin S, Dupont G.
Summary: Little is known about injury prevention practices in professional football clubs. The purpose of this study was therefore to determine the current perceptions and practices of premier league football clubs internationally concerning risk factors, testing and preventative exercises for non-contact injuries. A survey was administered to 93 premier league football clubs internationally. The survey included four sections: (1) persons involved in the injury prevention programme: position, quantity, role, qualification; (2) perceptions regarding non-contact injury risk factors; (3) tests used to identify non-contact injury risk and (4) non-contact injury prevention exercises used, their perceived effectiveness and implementation strategies. 44 surveys were successfully returned (47%). The position of physiotherapist was the most represented position in the injury prevention programme. The top five perceived risk factors in rank order were previous injury, fatigue, muscle imbalance, fitness and movement efficiency. The five most commonly used tests to identify injury risk (in rank order) were functional movement screen, questionnaire, isokinetic dynamometry, physical tests and flexibility. The top five exercises used by clubs were (also in rank order) eccentric exercise, balance/proprioception, hamstring eccentric, core stability and, sharing the fifth position, Nordic hamstring and gluteus activation. The survey revealed the most common perceptions and practices of premier league football clubs internationally regarding risk factors, testing and preventative exercises. The findings can enable reduction of the gap between research and practice.


#7 Importance of Muscle Power Variables in Repeated and Single Sprint Performance in Soccer Players
Reference: Journal of Human Kinetics. 40: 201-222, 2014.
Authors: Lopez-Segovia M, Dellal A, Chamari K, Gonzales-Badillo JJ
Summary: This study examined the relationship between lower body power and repeated as well as single sprint performance in soccer players. The performance of nineteen male soccer players was examined. The first testing session included the countermovement jump (CMJL) and the progressive full squat (FSL), both with external loads. Power in the CMJL and FSL was measured with each load that was lifted. The second session included a protocol of 40-m repeated sprints with a long recovery period (2 min). The number of sprints executed until there was a 3% decrease in performance for the best 40-m sprint time was recorded as a repeated sprint index (RSI). The RSI was moderately associated with power output relative to body mass in the CMJL and FSL (r = 0.53/0.54, p ≤ 0.05). The most and least powerful players (determined by FSL) showed significant differences in the RSI (9.1 ± 4.2 vs. 6.5 ± 1.6) and 10 m sprint time (p 0.01). Repeated and single sprints are associated with relatively lower body power in soccer players.


#8 Validation of the Loughborough Soccer Passing Test in young soccer players
Reference: J. Strength. Cond. Res. 28(5): 1418-1426, 2014.
Authors: Le Moal E., Rue O., Ajmol A., Abderrahman A. B., Hammami M. A., Ounis O. B., Kebsi W., Zouhal H.
Summary: The aim of this study was to examine the validity and reliability of the Loughborough Soccer Passing Test (LSPT) in adolescent soccer players. Eighty-seven players, aged 14-17 years, were recruited according to their playing level: elite (n = 44), sub-elite (n = 22), and non-elite (n = 21). Two attempts of the LSPT were performed at baseline. Players then completed 10 attempts over 3 weeks to familiarize themselves with the test. Subsequently, 2 main trials, separated by 1 week, were performed; the mean of the 2 attempts was recorded as the performance score. After familiarization, the performance scores showed significant differences (p < 0.01) between elite (40.3 +/- 8.3 seconds), sub-elite (58.1 +/- 10.2 seconds), and non-elite players (66.6 +/- 11.7 seconds). There was low-to-moderate reliability between trials with sub-elite (r = 0.35, p < 0.05) and non-elite players (r = 0.47, p < 0.05), but very good for elite players (r = 0.96, p < 0.05). Scores at baseline were better (p < 0.05) for elite players (51.0 +/- 9.3 seconds) compared with sub-elite (60.8 +/- 8.2 seconds) and non-elite players (69.0 +/- 11.1 seconds). The LSPT seems to be a valid and reliable protocol to assess differences in soccer skill performance in adolescent players and can distinguish players according to their playing level. The LSPT was able to distinguish different abilities without players undergoing any familiarization with the test, thus enabling it to be used for talent.