Matthew D. Portas

Factors associated with increased propensity for hamstring injury in English Premier League soccer players.

The aim of this study was to concurrently model the influence of a number of physical and performance parameters on subsequent incidence of hamstring injury in a squad of English Premier League soccer players. Thirty six healthy, male, elite, professional soccer players (age 22.6+/-5.2 years, height 1.81+/-0.08 m, mass 75.8+/-9.4 kg, lean mass 69.0+/-8.0 kg) were assessed during the first week of pre-season training for anthropometry, flexibility, lower limb strength and power, speed and agility. Over the subsequent 45 week competitive season all hamstring injuries were diagnosed and recorded. Multiple logistic regression analysis was performed to link individual physical and performance capabilities with propensity to sustain a hamstring injury. A model containing age, lean mass, non-counter movement jump (NCM) performance and active hip flexion range of movement (ROM) was significantly (p<0.05) associated with increased propensity for hamstring injury. Odds for sustaining an injury increased x 1.78 for each 1 year increase in age, x 1.47 for each 1cm increase in NCM and x 1.29 for each 1 degrees decrease in active range of hip flexion. Older, more powerful and less flexible soccer players are at greater risk of sustaining a hamstring injury. Support staff should identify such individuals and make appropriate interventions to minimise risk without compromising performance capabilities.

The effects of contrast bathing and compression therapy on muscular performance.

UNLABELLED Contrast bathing (CB) and compression garments (CG) are widely used to promote recovery. PURPOSE To evaluate CB and CG as regeneration strategies after exercise-induced muscle damage (EIMD). METHODS Baseline values of muscle soreness, serum creatine kinase (CK) and myoglobin (Mb), joint range of motion, limb girth, 10- or 30-m sprint, countermovement jump (CMJ), and five repetition maximum squat were completed by 26 young men who then undertook a resistance exercise challenge (REC) to induce EIMD: 6 x 10 parallel squats at 100% body weight with 5-s one repetition maximum eccentric squat superimposed onto each set. After the REC, subjects were separated into three intervention groups: CB, CG, and control (CONT). Forty-eight hours after REC, the subjects exercise performance was reassessed. CK and Mb were also measured +1, +24, and +48 h post-REC. RESULTS CK was elevated at +24 h ( upward arrow140%; upward arrow161%; upward arrow270%), and Mb was elevated at +1 h ( upward arrow523%; upward arrow458%; upward arrow682%) in CB, CG, and CONT. Within-group large effect sizes for loge[CK] were found for CB at +24 h (0.80) and +48 h (0.84). Area under the [Mb] curve was lower in CB compared with CG and CONT (P < or = 0.05). At +48 h, significant differences from baseline were found in all groups for CMJ (CG, downward arrow5.1%; CB, downward arrow4.4%; CONT, downward arrow8.5%) and soreness ( upward arrow213%; upward arrow284%; upward arrow284%). Soreness transiently fell at +1 h compared with post-REC in the CB group. At +48 h, midthigh girth increased in CB ( upward arrow1.4%) and CONT ( upward arrow1.6%), whereas 30-m sprint time increased in CG ( upward arrow2%). CONCLUSION No hierarchy of recovery effects was found. Neither contrast bathing nor compression acted to promote acute recovery from EIMD any more effectively than passive conditions, although contrast bathing may transiently attenuate postexercise soreness.

Motion analysis of match-play in elite U12 to U16 age-group soccer players

Abstract The aim of this study was to quantify the motion demands of match-play in elite U12 to U16 age-group soccer players. Altogether, 112 players from two professional soccer clubs at five age-group levels (U12–U16) were monitored during competitive matches (n = 14) using a 5 Hz non-differential global positioning system (NdGPS). Velocity thresholds were normalized for each age-group using the mean squad times for a flying 10 m sprint test as a reference point. Match performance was reported as total distance, high-intensity distance, very high-intensity distance, and sprint distance. Data were reported both in absolute (m) and relative (m · min−1) terms due to a rolling substitute policy. The U15 (1.35 ± 0.09 s) and U16 (1.31 ± 0.06 s) players were significantly quicker than the U12 (1.58 ± 0.10 s), U13 (1.52 ± 0.07 s), and U14 (1.51 ± 0.08 s) players in the flying 10 m sprint test (P < 0.001). The U16 age-group covered significantly more absolute total distance (U16 > U12, U13, U14), high-intensity distance (U16 > U12, U13, U14, U15), very high-intensity distance (U16 > U12, U13), and sprint distance (U16 > U12, U13) than their younger counterparts (P < 0.05). When the data are considered relative to match exposure, few differences are apparent. Training prescription for youth soccer players should consider the specific demands of competitive match-play in each age-group.

Re-examination of the post half-time reduction in soccer work-rate

OBJECTIVES To re-examine the work-rate of soccer players immediately after a passive half-time interval with an alternative approach to data reduction and statistical contrasts. DESIGN Time-motion analysis data (5Hz global positioning system), were collected from 20 elite youth players (age: 17±1 years) during 21 competitive league fixtures (5±3 matches per player). METHODS Physical performances were categorised into total distance covered, total low-speed running (0-14.9kmh(-1)) and total high-speed running (15.0-35.0kmh(-1)). These dependent variables were subsequently time averaged into pre-determined periods of 5-, 15- and 45-min duration, and expressed in relative (mmin(-1)) terms to allow direct comparisons between match periods of different lengths. During the 15-min half-time interval players were passive (seated rest). RESULTS There was a large reduction in relative total distance covered (effect size - standardised mean difference - 1.85), low-speed running (effect size -1.74) and high-speed running (effect size -1.37) during the opening 5-min phase of the second half (46-50min) when compared to the first half mean (0-45min). When comparing the 51-55 and 56-60-min periods, effect sizes were trivial for relative total distance covered (effect size -0.13; -0.04), low-speed running (effect size -0.10; -0.11) and small/trivial for high-speed running (-0.39; 0.11). CONCLUSIONS Using a more robust analytical approach, the findings of this study support and extend previous research demonstrating that players work-rate was markedly lower in the first 5-min after a passive half-time interval, although we observed this phenomenon to be transient in nature. Time-motion analysts might re-consider their data reduction methods and comparators to distinguish within-match player work-rate trends.

The Interchangeability of Global Positioning System and Semiautomated Video-Based Performance Data During Elite Soccer Match Play

Harley, JA, Lovell, RJ, Barnes, CA, Portas, MD, and Weston, M. The interchangeability of GPS and semiautomated video-based performance data during elite soccer match play. J Strength Cond Res 25(8): 2334-2336, 2011—In elite-level soccer, player motion characteristics are commonly generated from match play and training situations using semiautomated video analysis systems and global positioning system (GPS) technology, respectively. Before such data are used collectively to quantify global player load, it is necessary to understand both the level of agreement and direction of bias between the systems so that specific interventions can be made based on the reported results. The aim of this report was to compare data derived from both systems for physical match performances. Six elite-level soccer players were analyzed during a competitive match using semiautomated video analysis (ProZone® [PZ]) and GPS (MinimaxX) simultaneously. Total distances (TDs), high speed running (HSR), very high speed running (VHSR), sprinting distance (SPR), and high-intensity running distance (HIR; >4.0 m·s-1) were reported in 15-minute match periods. The GPS reported higher values than PZ did for TD (GPS: 1,755.4 ± 245.4 m; PZ: 1,631.3 ± 239.5 m; p < 0.05); PZ reported higher values for SPR and HIR than GPS did (SPR: PZ, 34.1 ± 24.0 m; GPS: 20.3 ± 15.8 m; HIR: PZ, 368.1 ± 129.8 m; GPS: 317.0 ± 92.5 m; p < 0.05). Caution should be exercised when using match-load (PZ) and training-load (GPS) data interchangeably.

The effect of a short practical warm-up protocol on repeated sprint performance.

Abstract Taylor, JM, Weston, M, and Portas, MD. The effect of a short practical warm-up protocol on repeated sprint performance. J Strength Cond Res 27(7): 2034–2038, 2013—The aim of our study was to investigate the effect of a short, practical, 2-phase warm-up on repeated sprint performance when compared with more traditional warm-up protocols that contain stretching activities. Eleven subelite male soccer players completed a warm-up protocol that commenced with 5 minutes jogging at approximately 65% of maximal heart rate, followed by no stretching, static stretching, or dynamic stretching and finishing with a task-specific high-intensity activity. Using a crossover design, the 3 warm-up protocols were performed in a counterbalanced order with at least 48 hours between sessions. Repeated sprint performance was measured using a repeated sprint test that consisted of 6 × 40-m maximal sprints interspersed with a 20-second recovery. There were trivial differences in mean sprint time (0.2%) and posttest blood lactate (3.1%) between the 2-phase warm-up and the 3-phase warm-up that included dynamic stretching, whereas the short warm-up had a possibly detrimental effect on fastest sprint time (0.7%). Fastest (−1.1%) and mean (−1.2%) sprint times were quicker and posttest blood lactates were higher (13.2%) after the 2-phase warm-up when compared with the 3-phase warm-up that included static stretching. Although it is not harmful to complete a traditional 3-phase warm-up that includes dynamic stretching, it appears practical for athletes preparing for activities dependent on repeated sprint ability to complete a 2-phase warm-up consisting of a cardiovascular and specific high-intensity activity.

Within-Match PlayerLoad™ Patterns during a Simulated Soccer Match: Potential Implications for Unit Positioning and Fatigue Management

PURPOSE To assess the acute alterations in triaxial accelerometry (PlayerLoad [PL(VM)]) and its individual axial planes (anteroposterior PlayerLoad [PL(AP)], mediolateral PlayerLoad [PL(ML)], and vertical PlayerLoad [PL(V)]) during a standardized 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. METHODS Semiprofessional (n = 5) and university (n = 15) soccer players completed 3 trials (1 familiarization, 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 center of mass (COM). RESULTS There were no between-halves differences in PL(VM); however, within-half increases were recorded at the COM, but only during the 1st half at the SCAP. Greater contributions to PL(VM) were provided by PL(V) and PL(ML) when derived from the SCAP and COM, respectively. PL(VM) (COM 1451 ± 168, SCAP 1029 ± 113), PL(AP) (COM 503 ± 99, SCAP 345 ± 61), PL(ML) (COM 712 ± 124, SCAP 348 ± 61), and PL(V) (COM 797 ± 184, SCAP 688 ± 124) were significantly greater at the COM than at the SCAP. Moderate and high test-retest reliability was observed for PlayerLoad and its individual planes at both locations (ICC .80-.99). CONCLUSIONS 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.

The effectiveness of 4 weeks of fundamental movement training on functional movement screen and physiological performance in physically active children.

Abstract Wright, MD, Portas, MD, Evans, VJ, and Weston, M. The effectiveness of 4 weeks of fundamental movement training on Functional Movement Screen and physiological performance in physically active children. J Strength Cond Res 29(1): 254–261, 2015—The effectiveness of fundamental movement training interventions in adolescents is not fully understood. The Functional Movement Screen (FMS) may provide means of evaluating the effectiveness of such programs alongside traditional tests of physiological performance. Twenty-two children completed the FMS, plank, side plank, sit and reach, and multistage fitness test. Participants were pair matched by total FMS score and assigned to control or intervention. The intervention group received a weekly 4 × 30-minute training sessions with an emphasis on movement quality, whereas the control group was involved in generic multisport activity. A smallest worthwhile effect of 0.2 between-participant SDs was set a priori for all measures except total FMS score for which a change of 1 unit was chosen. When compared with the control, our intervention had a likely trivial effect for FMS score (0.2 Arbitrary Units [AU], 90% confidence limits ±1.2 AU), a very likely small beneficial effect for plank score (87 ± 55%), but a possibly small harmful effect for side plank score (−22 ± 49%). A likely trivial effect was observed for the sit and reach test (0.3 ± 15%), whereas the effect of the training intervention on predicted was unclear (−0.3 ± 11%). Unexpectedly, generic multisport activity enhanced both side plank and sit and reach test performances in the control group. These results demonstrated that short-term interventions might affect specific isolated components of fitness but not FMS performance.

Maturational effect on Functional Movement Screen™ score in adolescent soccer players

OBJECTIVES The effect of maturity on Functional Movement Screen (FMS) scores in elite, adolescent soccer players was examined. DESIGN A cross-sectional observational study was completed. METHODS Participants were 1163 male English Football League soccer players (age 8-18 years). Players were mid-foundation phase (MF) (U9); late foundation phase (LF) (U10 and U11); early youth development phase (EYD) (U12 and U13); mid-youth development (MYD) phase (U14-U15); Late Youth Development Phase (LYD) (U16) and early professional development phase (EPD) (U18). Age from peak height velocity was estimated and players were categorized as pre- or post-peak height velocity (PHV). To analyse where differences in FMStotal score existed we separated the screen into FMSmove (3 movement tests); FMSflex (2 mobility tests) and FMSstab (2 stability tests). RESULTS FMStotal median score ranged from 11 at MF to 14 for EPD. There was a substantial increase (10%) in those able to achieve a score of ≥14 on FMStotal in those who were post-PHV compared to pre-PHV. This was explained by a substantial increase in those achieving a score of ≥4 on FMSstab (21%). There was a substantial increase in the proportion of players who achieved the FMStotal threshold of ≥14 with an increase of 47.5 (41.4-53.6)% from the MF phase to the EPD phase due to improvements in FMSmove and FMSstab. CONCLUSIONS PHV and maturity have substantial effects on FMS performance. FMS assessment appears to be invalid for very young players. Findings are relevant to those analyzing movement in soccer players.

Within-Season Variation of Fitness in Elite Youth Female Soccer Players

Within-Season Variation of Fitness in Elite Youth Female Soccer Players The within-season variation in fitness measures of elite youth female soccer players (<18 years of age) has not been investigated previously. Further knowledge of this area could allow more effective periodization of training, whilst also enabling coaches to design appropriate long-term athlete development models. This study investigated the within-season variation of fitness test performance in elite youth female soccer players. In elite youth female soccer players, acceleration, sprint and CoD performance decreased over the course of a season, whilst RSA performance improved in U13 players. Coaches should consider the impact of physiological preparation on performance when working with youth female soccer players, implementing training interventions and recovery strategies accordingly to prevent reduced performance capacity during competition.