Latest research in football - week 1 - 2016

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Muscle strength and anaerobic performance in football players with cerebral palsy
Reference: Disabil Health J. 2015 Dec 1. pii: S1936-6574(15)00173-9. doi: 10.1016/j.dhjo.2015.11.003. [Epub ahead of print]
Authors: Yanci J, Castagna C, Los Arcos A, Santalla A, Grande I, Figueroa J, Camara J
Summary: This is the first study that quantified the anaerobic performance in football players with cerebral palsy (CP). This study aimed to examine anaerobic fitness in a population of football players with CP using vertical jumping (VJ) and Wingate tests. Twelve players (age 26.8 ± 4.8 yr, body mass 66.2 ± 4.8 kg, height 173.7 ± 6.4 cm, body mass index 22.2 ± 1.9 kg m-2) from the Spanish National Football Team with CP which had 9.4 ± 3.7 years of playing experience performed the VJ and Wingate anaerobic tests. Vertical jump height was 20.0 ± 1.2 cm for squat jump (HSJ) and 23.9 ± 5.4 cm for countermovement jump (HCMJ). Wingate test peak power (PPOW) was 490.6 ± 125.8 W (7.35 ± 1.53 W kg-1). HCMJ was largely (r = -0.631, p = 0.028) and very-largely (r = -0.710, p = 0.01) associated with PPOW (W kg-1) and mean power output (MPOW) (W kg-1), respectively. Squat jump test peak power (W) showed a large association (r = -0.656, p = 0.021) with MPOW (W and W kg-1). The CMJ height resulted 19.5% higher than SJ. Results showed low VJ and anaerobic capacity of football players with CP compared to national players without CP and the general population. In football players with CP the difference (19.5%) between VJ with or without countermovement (CMJ-SJ) was higher than reported for national players without CP. Further studies examining the effect of football practice on neuromuscular performance in subjects with CP are warranted.

#2 Reliability and validity of Yo-Yo tests in 9- to 16-year-old football players and matched non-sports active schoolboys
Reference: Eur J Sport Sci. 2015 Dec 30:1-9. [Epub ahead of print]
Authors: Póvoas SC, Castagna C, Soares JM, Silva PM, Lopes MV, Krustrup P
Summary: The purpose of this study was to examine the test-retest reliability and construct validity of three age-adapted Yo-Yo intermittent tests in football players aged 9-16 years (n = 70) and in age-matched non-sports active boys (n = 72). Within 7 days, each participant performed two repetitions of an age-related intensity-adapted Yo-Yo intermittent test, i.e. the Yo-Yo intermittent recovery level 1 children's test for 9- to 11-year-olds; the Yo-Yo intermittent endurance level 1 for 12- to 13-year-olds and the Yo-Yo intermittent endurance level 2 test for 14- to 16-year-olds. Peak heart rate (HRpeak) was determined for all tests. The distance covered in the tests was 57% (1098 ± 680 vs. 700 ± 272 m), 119% (2325 ± 778 vs. 1062 ± 285 m) and 238% (1743 ± 460 vs. 515 ± 113 m) higher (p ≤ .016), respectively for football-trained than for non-sports active boys aged 9-11, 12-13 and 14-16 years. The typical errors of measurement for Yo-Yo distance, expressed as a percentage of the coefficient of variation (confidence interval), were 11.1% (9.0-14.7%), 10.1% (8.1-13.7%) and 8.5% (6.7-11.7%) for football players aged 9-11, 12-13 and 14-16 years, respectively, with corresponding values of 9.3% (7.4-12.8%), 10.2% (8.1-14.0%) and 8.5% (6.8-11.3%) for non-sports active boys. Intraclass correlation coefficient values for test-retest were excellent in both groups (range: 0.844-0.981). Relative HRpeak did not differ significantly between the groups in test and retest. In conclusion, Yo-Yo intermittent test performances and HRpeak are reliable for 9- to 16-year-old footballers and non-sports active boys. Additionally, performances of the three Yo-Yo tests were seemingly better for football-trained than for non-sports active boys, providing evidence of construct validity.

#3 Practice effects on intra-team synergies in football teams
Reference: Hum Mov Sci. 2015 Dec 18;46:39-51. doi: 10.1016/j.humov.2015.11.017. [Epub ahead of print]
Authors: Silva P, Chung D, Carvalho T, Cardoso T, Davids K, Araújo D, Garganta J
Summary: Developing synchronised player movements for fluent competitive match play is a common goal for coaches of team games. An ecological dynamics approach advocates that intra-team synchronization is governed by locally created information, which specifies shared affordances responsible for synergy formation. To verify this claim we evaluated coordination tendencies in two newly-formed teams of recreational players during association football practice games, weekly, for fifteen weeks (thirteen matches). We investigated practice effects on two central features of synergies in sports teams - dimensional compression and reciprocal compensation here captured through near in-phase modes of coordination and time delays between coupled players during forward and backwards movements on field while attacking and defending. Results verified that synergies were formed and dissolved rapidly as a result of the dynamic creation of informational properties, perceived as shared affordances among performers. Practising once a week led to small improvements in the readjustment delays between co-positioning team members, enabling faster regulation of coordinated team actions. Mean values of the number of player and team synergies displayed only limited improvements, possibly due to the timescales of practice. No relationship between improvements in dimensional compression and reciprocal compensation were found for number of shots, amount of ball possession and number of ball recoveries made. Findings open up new perspectives for monitoring team coordination processes in sport.

#4 Testosterone Concentration and lower limb power over and entire competitive season in elite young soccer players
Reference: J Strength Cond Res 29(12): 3380–3385, 2015
Authors: Arruda, AFS, Aoki, MS, Freitas, CG, Spigolon, LMP, Franciscon, C, and Moreira, A
Summary: Testosterone concentration and lower limb power over an entire competitive season in elite young soccer players.—The aim of this study was to investigate salivary T changes and its relationship with power performance over a 1-year competitive season in elite under 15 (U15) and under 17 (U17) soccer players. Soccer players were recruited from 1 soccer club that has been participated in the main state and national leagues for these age groups. The soccer players were divided into 2 age categories (U15, n = 16 and U17, n = 23). A resting saliva sample was taken to determine T level, and power was assessed using the countermovement jump test with a bar of 30% of body mass on the athletes' shoulders on 3 occasions (T1: beginning of the competitive season, T2: end of the regular season, and T3: end of the playoffs). There was a decrease in T concentration at the end of the competitive season (T3) as compared with the beginning of the season (T1) for both age categories (p ≤ 0.05). Conversely, power performance parameters were increased for both age groups (U15: mean power and relative mean power and U17: peak power, mean power, relative peak power, and relative mean power; p ≤ 0.05). No significant correlation was identified between the relative changes in T concentration and power performance in both groups. The findings of this study suggest that T changes and power changes are not related.

#5 Cardiac Parasympathetic Reactivation in Elite Soccer Players During Different Types of Traditional High-Intensity Training Exercise Modes and Specific Tests: Interests and Limits
Reference: Asian J Sports Med. 2015 Dec;6(4):e25723. doi: 10.5812/asjsm.25723. Epub 2015 Dec 1.
Aurhors: Dellal A, Casamichana D, Castellano J, Haddad M, Moalla W, Chamari K5.
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Summary: The cardiac parasympathetic reactivation is currently used in soccer with a daily or weekly monitoring. However, previous studies have not investigated how this cardiac parasympathetic reactivation is in elite soccer players along different types of traditional high-intensity training exercise and specific tests. In this context, the present study aim to analyse it and to determine the interests and limits of this type of physiological information. The present study aims to examine how different traditional training exercise modes affect the cardiac parasympathetic reactivation function in elite soccer players. Twenty-two international soccer players participating in UEFA Champion's League took part in this study (age: 24.3 ± 4.2 years; height: 178.1 ± 6.2 cm; body mass: 80.3 ± 5.7 kg). Players performed different training methods including: short-duration intermittent exercises (INT) in-line and with changes of direction (COD) (10 - 10 seconds, 15 - 15 seconds, 30 - 30 seconds, e.g. an alternance of 10 - 10 seconds is 10 seconds of running according to the maximal aerobic speed (MAS) and 10-sec of recovery), INT including agility and technical skills (8 - 24-seconds), small-sided-games (SSGs) with and without goalkeepers (2 vs. 2, 3 vs. 3, 4 vs. 4), and repeated sprint ability (RSA) efforts (10 × 20 m, 10 × 30 m, 15 × 20 m). Heart rate (HR) decline was recorded 3 minutes after each exercise. HR declines were greater after the RSA compared to SSGs (P < 0.001) and INT (P < 0.01), especially at 1 min post-exercise. In addition, when the analysis focused on each type of exercise, greater HR declines were observed in on-field players at 1 minute when there was: inclusion of goalkeepers in SSGs (for 2 vs. 2 and 3 vs. 3, P < 0.01); increase of sprint distances or number of sprint repetitions in RSA (P < 0.01); increase of intensity (% of maximal aerobic speed), and the use of COD or inclusion of technical skills during INT, especially for the 30 - 30-seconds. This study revealed that cardiac parasympathetic reactivation function varied after INT, RSA and SSG, but also according to the rules manipulation. Therefore, this study provides interesting information for the training monitoring and players' recovery profile, with the aim of facilitating a more efficient planning and manipulation of training recovery strategies according to their fitness markers.

#6 Isolated Proximal Tibiofibular Dislocation during Soccer
Reference: Case Rep Emerg Med. 2015;2015:657581. doi: 10.1155/2015/657581. Epub 2015 Dec 2.
Authors: Chiu C, Sheele JM
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Summary: Proximal tibiofibular dislocations are rarely encountered in the Emergency Department (ED). We present a case involving a man presenting to the ED with left knee pain after making a sharp left turn on the soccer field. His physical exam was only remarkable for tenderness over the lateral fibular head. His X-rays showed subtle abnormalities of the tibiofibular joint. The dislocation was reduced and the patient was discharged from the ED with orthopedic follow-up.

#7 Effect of leg dominance on change of direction ability amongst young elite soccer players
Reference: J Sports Sci. 2015 Dec 29:1-7. [Epub ahead of print]
Authors: Rouissi M, Chtara M, Owen A, Chaalali A, Chaouachi A, Gabbett T, Chamari K
Summary: Young soccer players often use one particular dominant leg (DL) to perform dynamic movements which require strength, resulting in leg asymmetry. The aim of this study was to compare, in young soccer players, the effect of using DL and non-dominant leg (NDL) on time performance of two change of direction (COD) manoeuvres in several angles of COD. Seventy-three young male soccer players (mean ± SD, age: 16.1 ± 1.8 year) participated in this study. Players performed 10-m sprints, either in a straight line or with a COD (5 m straight ahead and a turn of 45°, 90°, 135° and 180° to the opposite side of the DL or NDL). Testing for COD speed was conducted over two different manoeuvres: (1) sidestepping and (2) bypass. Maximal isometric voluntary contraction of the knee extensors/flexors and hip abductors/adductors was also measured using a handheld dynamometer. For sidestepping, COD performance with use of the DL was significantly better compared to the NDL (P < 0.05) in all angles of COD. However, bypass COD performance through use of the DL was better compared to the NDL only when turning at 135°. Additionally, strength of the knee extensors/flexors and hip abductors of the DL was significantly (P < 0.05) greater than the NDL. The use of the DL allows better COD performance than the NDL when sidestepping manoeuvre is used. However, the DL allows better COD performance than the NDL only at 135° with the use of the bypass manoeuvre. Furthermore, the greater strength of the DL compared to the NDL may contribute to COD performance difference between legs.

#8 Development of perceived competence, tactical skills, motivation, technical skills, and speed and agility in young soccer players
Reference: J Sports Sci. 2015 Dec 28:1-8. [Epub ahead of print]
Authors: Forsman H, Gråstén A, Blomqvist M, Davids K, Liukkonen J, Konttinen N
Summary: The objective of this 1-year, longitudinal study was to examine the development of perceived competence, tactical skills, motivation, technical skills, and speed and agility characteristics of young Finnish soccer players. We also examined associations between latent growth models of perceived competence and other recorded variables. Participants were 288 competitive male soccer players ranging from 12 to 14 years (12.7 ± 0.6) from 16 soccer clubs. Players completed the self-assessments of perceived competence, tactical skills, and motivation, and participated in technical, and speed and agility tests. Results of this study showed that players' levels of perceived competence, tactical skills, motivation, technical skills, and speed and agility characteristics remained relatively high and stable across the period of 1 year. Positive relationships were found between these levels and changes in perceived competence and motivation, and levels of perceived competence and speed and agility characteristics. Together these results illustrate the multi-dimensional nature of talent development processes in soccer. Moreover, it seems crucial in coaching to support the development of perceived competence and motivation in young soccer players and that it might be even more important in later maturing players.

#9 Development and validation of the Perceived Game-Specific Soccer Competence Scale
Reference: J Sports Sci. 2015 Dec 28:1-9. [Epub ahead of print]
Authors: Forsman H, Gråstén A, Blomqvist M, Davids K, Liukkonen J, Konttinen N
Summary: The objective of this study was to create a valid, self-reported, game-specific soccer competence scale. A structural model of perceived competence, performance measures and motivation was tested as the basis for the scale. A total of 1321 soccer players (261 females, 1060 males) ranging from 12 to 15 years (13.4 ± 1.0 years) participated in the study. They completed the Perceived Game-Specific Soccer Competence Scale (PGSSCS), self-assessments of tactical skills and motivation, as well as technical and speed and agility tests. Results of factor analyses, tests of internal consistency and correlations between PGSSCS subscales, performance measures and motivation supported the reliability and validity of the PGSSCS. The scale can be considered a suitable instrument to assess perceived game-specific competence among young soccer players.

#10 Effects of an eight-week proprioceptive neuromuscular facilitation stretching program on kicking speed and range of motion in young male soccer players
Reference: J Strength Cond Res 29(12): 3412–3423, 2015
Authors: Akbulut, T, Agopyan, A
Summary: The aim of this study was to determine the effect of the 8-week proprioceptive neuromuscular facilitation (PNF) exercises that were carried out on lower extremity on kicking speed and range of motion (ROM) performance in young soccer players. Twenty-four soccer players (15.6 ± 0.4 years) were selected from nonprofessional young soccer team. All players' height, weight, ROM (ankle plantar and dorsal flexions, hip flexions and extensions), and kicking speed tests were evaluated before and after 8 weeks. The participants were divided into PNF (n = 11) and control (n = 11) groups. Both groups continued technical and tactical soccer training together 3 days (120 min·d−1) a week. The PNF group attended additionally unassisted PNF–contract-relax (CR) stretching through 8 weeks, 2 days per week, 20 minutes' session duration. The control group did not participate in any additional PNF stretching sessions. There were significant differences in kicking speed, right ankle active dorsal flexion, and hip active flexion (right and left) (p ≤ 0.05) of the PNF group, whereas there were no significant differences between groups in left ankle active dorsal flexion, hip active extension (right and left), and ankle active plantar flexion (right and left) (p > 0.05). We conclude that an 8-week unassisted PNF-CR improved on the ROM of particular lower extremity joints and the kicking speed in the young male soccer players. These results provide strength and conditioning coaches with a practical way to use unassisted PNF-CR in warm-up for positive improvements in the ROM of the hip and ankle and the applications of the kicking speed.


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