Latest research in football - week 26 - 2015

#1 Imaging study of ankle injury in professional soccer player of males
Reference: Zhonghua Yi Xue Za Zhi. 2015 May;95(17):1290-4. [Article in Chinese]
Authors: Li S, Zhao W, Hao S, Hu S, Zhang R, Zhang X
Summary: The purpose of the study was to analyze the imaging abnormal findings of ankle injuries in professional soccer player of males. The thirty-two professional soccer players in local region soccer club had been selected as research objects from March 2014 to January 2015, and all were men. Average age was 22.03 ± 3.0 years old (19-33 years); the average age was 8.6 ± 2.0 years old that began to engage in professional football training, and average time of engaged in football sports was 13 ± 4 years (7-27 years). X-ray examination was used VM DR (Philips Co.), anteroposterior and lateral position of ankle joints. CT scan was used MSCT of 64 rows detector (Aquilion 64, TOSHIBA Co.). After routine scan, raw data was transmitted to the workstation and then reconstructed to be axial, sagittal, coronal imaging. MR examination was used 1.5 T superconducting equipment system (Achieva Dual, Philips Co.) and with ankle joint special phased array coil. TSE sequence be used to scan routine axial T2-weighted imaging; coronal T1-weighted imaging; coronal PWI; and sagittal T2-weighted imaging with fat suppressed. The sagittal PWI scan was used with Isotropic with fat suppressed FFE sequence. The X-ray examination was finished for 28 person and 51 ankle joints. 26 person and 52 ankle joints were completed CT scan and reconstructed imaging for all joints. MR examination was finished in 30 person and 51 ankle joints. On X-ray and CT display that the abnormal changes of the talus is most commonly found that the incidence of "dolphin mouth" like protrusion at posterior edge was 35 ankles (rate of occurrence was 68.6%), the triangle prominence at out edge was 45 ankles (rate of occurrence was 88.2%). It also was found that 8 lateral malleolus have osteophytes, 5 ankles have medial malleolus osteophytes and 12 ankles have loose bodies at posterior ankle. MRI showed that 30 ankles were the anterior talofibular ligaments injury and incidence was 58.82%, 26 ankles were posterior talofibular ligaments injury (incidence was 51.0%), 25 ankles were calcanofibular ligaments injury (incidence was 49.0%), 29 ankles was the synovitis and local effusion at posterior ankle (incidence was 56.9%), the partial ligaments injured of deltoid ligaments were usually found and entirely torn were very rare (only three ankles). The former groups and shallow ligaments of deltoid ligaments were prone to injury. The common tendon disease of injury was tenosynovitis, 18 flexor hallucis longus tenosynovitis, 13 posterior tibialis tenosynovitis,7 flexor digitorium tenosynovitis, 5 peroneus longus tenosynovitis, 2 peroneus brevis tenosynovitis and 6 Achilles tendinopathy. Tendinosis and tendon degeneration was relatively rare. The professional soccer players have been easily lead to the anatomic abnormal and pathological changes in the bones, ligaments and tendons due to long-term training and competition. The majority changes were chronic injury. Imaging examination can be found the abnormal changes of ankle and could help athletes, coachs, doctors to understand and assess the ankle structure and functional status.


#2 Within-Match PlayerLoad™ Patterns During a Simulated Soccer Match (SAFT90): Potential Implications for Unit Positioning and Fatigue Management
Reference: Int J Sports Physiol Perform. 2015 Jun 24. [Epub ahead of print]
Authors: Barrett S, Midgley AW, Towlson C, Garrett A, Portas M, Lovell R.
Summary: The principle aim of the study was to assess the acute alterations in tri-axial accelerometry (PlayerLoad™; PLVM) and its individual axial-planes (anterior-posterior-PlayerLoad™ [PLAP], medial-lateral-PlayerLoad™ [PLML] and vertical-PlayerLoadTM [PLV]) during a standardised 90-min soccer match-play simulation (SAFT90). Secondary aims of the study were to assess the test-retest reliability and anatomical location of the devices. Semi-professional (n=5) and University (n=15) soccer players completed 3 trials (1 familiarisation, 2 experimental) of SAFT90. PlayerLoad™ and its individual planes were measured continuously using micromechanical-electrical systems (MEMS) positioned at the scapulae (SCAP) and near the centre of mass (COM). There were no between-half differences in PLVM, however, within-half increases were recorded at the COM, but only during the 1st half at the SCAP. Greater contributions to PLVM were provided by PLV and PLML when derived from the SCAP and COM, respectively. PLVM (COM: 1451 ± 168; SCAP: 1029 ± 113), PLAP (COM: 503 ± 99; SCAP: 345 ± 61), PLML (COM: 712 ± 124; SCAP: 348 ± 61) and PLV (COM: 797 ± 184; SCAP: 688 ± 124) were significantly greater at the COM compared to the SCAP. Moderate and high test-retest reliability was observed for PlayerLoad™ and its individual planars at both locations (ICC: 0.80-0.99). PlayerLoad™ and its individual planes are reliable measures during SAFT90 and detected within-match changes in movement strategy when the unit was placed at the COM, which may have implications for fatigue management. Inferring alterations in lower-limb movement strategies from MEMS units positioned at the SCAP should be undertaken with caution.


#3 Incidence and factors associated with injuries among adolescent players in an amateur soccer tournament in Southwest, Nigeria
Reference: J Sports Med Phys Fitness. 2015 Jun 26. [Epub ahead of print]
Authors: Olumide A, Ajide K.
Summary: The study was conducted to determine the incidence and risk factors associated with injuries among adolescents participating in an amateur soccer tournament in Ibadan, Nigeria. A prospective study was conducted among 90 participants (66 players and 24 substitutes) from six all-male teams with each team comprising 11 players. A total of six matches, each lasting 60 minutes (132 player-hours) were played in the tournament. Players were observed during all matches and followed up for up to two weeks after the final match. The association between selected risk factors and injury occurence was assessed using Chisquare test. Players mean age was 16.1 (± 1.8) years. Twelve (13.3%) of the 90 players were involved in 15 injury events. The injury incidence was 113.6 injuries per 1000 player hours (95% CI: 56.1-171.1) and 12 (80.0%) of all injuries occurred within 15 minutes of the end of each half of the match. Injuries often affected the lower limb 10 (58.8%), and the upper limb 6 (35.3%). Common injuries sustained were abrasions, 11 (64.6%), sprains, 3 (17.6%) and contusions 2 (11.8%). Eighty percent of injuries were due to collision with another player. All injuries were slight to mild as all the injured players returned to practice or games within five days of sustaining the injury. Dominant playing foot (mainly left foot or both feet) was associated with a higher incidence of injuries (χ2 = 7.321; p=0.018). Injury incidence was relatively high although injuries were mild. Measures to minimize injuries following player-to-player contact would be beneficial for adolescent soccer players in our study setting.


#4 The Contribution of Trunk Axial Kinematics to Post-Strike Ball Velocity During Maximal in-Step Soccer Kicking
Reference: J Appl Biomech. 2015 Jun 18. [Epub ahead of print]
Authors: Fullenkamp AM, Campbell BM, Laurent CM, Lane AP
Summary: To date, soccer kicking biomechanical analyses have focused predominantly on lower-extremity motions, with little emphasis on the trunk and upper-body. The purpose of this study was to evaluate differences in trunk axial kinematics between novice (n = 10) and skilled (n = 10) participants, as well as to establish the relationship of trunk axial motion and sagittal plane thigh rotation to post-strike ball velocity. 3D body segmental motion data were captured using high-resolution motion analysis (120 Hz) while each participant completed five maximal instep soccer-style kicks. The results demonstrate that skilled participants utilize 53% greater axial trunk ROM compared to novice participants (p < 0.01), as well as 62% greater peak trunk rotation velocity (p < 0.01). The results also showed a moderate, positive correlation of peak trunk rotation velocity with post-strike ball velocity (r = 0.57; p < 0.01), and peak hip flexion velocity with post-strike ball velocity (r = 0.63; p < 0.01). The current study highlights the potential for trunk rotation-specific training to improve maximum instep kick velocity in developing soccer athletes.


#5 No association between surface shifts and time-loss overuse injury risk in male professional football
Reference: J Sci Med Sport. 2015 Jun 6. pii: S1440-2440(15)00126-7. doi: 10.1016/j.jsams.2015.06.001. [Epub ahead of print]
Authors: Kristenson K, Bjørneboe J, Waldén M, Ekstrand J, Andersen TE, Hägglund M
Summary: The purpose was to investigate frequent surface shifts and match play on an unaccustomed surface as potential risk factors for injury in Scandinavian male professional football. Thirty two top-division clubs (16 Swedish, 16 Norwegian) were followed during seasons 2010 and 2011. The influence from (1) number of surface shifts (between artificial turf and grass) during five-match sequences, and (2) match play on an unaccustomed surface (other surface than on the home venue) on subsequent overuse injury risk was evaluated with generalized estimating equations (GEE). GEE results are presented with risk ratios and 95% confidence interval (CI). Injury rate was expressed as time loss injuries/1000h, and compared between groups with a rate ratio and 95% CI. No association was found between the number of surface shifts and subsequent overuse injury risk (risk ratio 1.01, 95% CI 0.91-1.12). Furthermore, no difference was seen in subsequent overuse injury risk after match play on unaccustomed compared with accustomed surface (risk ratio 1.04, 95% CI 0.78-1.38). Grass clubs (grass installed at home venue) had a lower match injury rate when playing away matches on artificial turf compared with away matches on grass (rate ratio 0.66, 95% CI 0.40-0.89). This study showed no association between surface shifts or playing matches on an unaccustomed surface and time-loss injury risk in professional football, suggesting that clubs and players can cope with such surface transitions.

#6 Influence of the Number of Players and the Relative Pitch Area per Player on Heart Rate and Physical Demands in Youth Soccer
Reference:  J Strength Cond Res 29(6): 1683–1691, 2015
Authors: Castellano, J, Puente, A, Echeazarra, I, and Casamichana, D.
Summary: The aim of this study was to analyze the influence of different large-sided games on the physical and physiological variables in under-13 soccer players. The effects on heart rate (HR) and physical demands of different number of players (NP) (7, 9, and 11) together with the relative pitch area (RPA) (100, 200, and 300 m2) during two 12-minute repetitions were analyzed in this study. The variables analyzed were mean, maximum and different intensity zones of HR; total distance (TD); work:rest ratio (W:R); player load (PL); 5 absolute and 3 relative speed categories. The results support the hypothesis that a change in pitch dimensions affects locomotor activity more than the NP does but also refute the hypothesis that the change in the NP has a greater effect on HR. To be more specific, an increase in the RPA per player (300/200/100 m2) was associated with higher values of the following variables: TD (2,250–2,314/2,003–2,148/1,766–1,845 m), W:R (0.5–0.6/0.4–0.5/0.3 arbitrary unit [AU]), PL (271–306/246–285/229–267 AU), %HRmean (85–88/85–89/81–83%), %HRmax (95–100/97–100/95–98%), and affected the percentage of time spent in both absolute (above 8 km·h−1) and relative speed (above 40% Vmax) categories (p ≤ 0.05, effect size: 0.31–0.85). These results may help youth soccer coaches to plan the progressive introduction of large-sided games so that task demands are adapted to the physiological and physical development of participants.


#7 Relationships Between Repeated Sprint Ability, Mechanical Parameters, and Blood Metabolites in Professional Soccer Players
Reference: J Strength Cond Res 29(6): 1673–1682, 2015
Authors: Morcillo, JA, Jiménez-Reyes, P, Cuadrado-Peñafiel, V, Lozano, E, Ortega-Becerra, M, and Párraga, J.
Summary: This study analyzed the acute metabolic and mechanical responses to a specific repeated sprint ability (RSA) test. Eighteen male professional soccer players from a team of the First Division of Spanish National League participated. A 12 × 30-m RSA test with 30-second recovery together with countermovement jump test (CMJ) pre a post RSA test was performed. Mechanical responses (i.e., height performance in CMJ and speed loss) and metabolic responses (i.e., blood lactate and ammonia concentrations) were measured before and after exercise. A related sample t-test was used to analyze CMJ height pre-post changes as well as to compare pre- and post-exercise lactate and ammonia levels. Countermovement jump height loss pre-post session (8%) was significant, and fatigue, measured as CMJ height loss, was strongly correlated to lactate (r = 0.97; p < 0.001) and ammonia (r = 0.92; p < 0.001) for all players. The relationships between the variables studied were determined by calculating the Pearson correlation coefficients. The metabolic stress developed during the effort can be estimated by controlling CMJ because of the high correlation between CMJ and blood lactate and ammonia concentrations. The high correlations found between mechanical (speed and CMJ height losses) and metabolic (lactate and ammonia) measures of fatigue highlight the utility and validity of using CMJ to monitor training load and quantify objectively neuromuscular fatigue during RSA.


#8 The Effect of Two Generic Aerobic Interval Training Methods on Laboratory and Field Test Performance in Soccer Players
Reference: J Strength Cond Res 29(6): 1666–1672, 2015
Authors: da Silva, JF, Nakamura, FY, Carminatti, LJ, Dittrich, N, Cetolin, T, and Guglielmo, LGA.
Summary: The purpose of this study was to compare the effects of 2 generic aerobic training models, based on peak running velocity in Carminatti's test (PVT-CAR) in U-20 elite soccer players. Seventeen soccer players (age: 17.9 ± 1.0 years; 178.6 ± 5.0 cm; 73.6 ± 6.6 kg; 11.1 ± 1.3%) from a team competing in a national junior league took part in the study. The athletes performed a series of pre- and posttraining tests (incremental test on a treadmill to determine the maximal oxygen uptake [V[Combining Dot Above]O2max], velocity at maximal oxygen uptake [vV[Combining Dot Above]O2], the lactate threshold [LT], and T-CAR). The interval training models applied were with 180° direction change (T12:12; n = 9) and without direction change (T6:6; n = 8). No significant interaction (time vs. group) was observed for the majority of variables analyzed (p > 0.05), although significant main effects in time were evident regarding peak treadmill velocity (PVTREAD) (F = 56.3, p < 0.0001), vV[Combining Dot Above]O2max (F = 35.8, p < 0.0001), LT (F = 57.7, p < 0.0001), and PVT-CAR (F = 52.9, p < 0.0001). Moreover, there was no significant change in V[Combining Dot Above]O2max between pre and posttraining period (F = 4.26, p = 0.056) in both training groups. Thus, it can be concluded that the prescribed training with and without direction change in the intensity of the PVT-CAR increases the PVTREAD, the vV[Combining Dot Above]O2max, the LT, and the PVT-CAR similarly.