An Exercise Protocol that Replicates Soccer Match-Play

Carbohydrate Nutrition and Skill Performance in Soccer

In soccer, players must perform a variety of sport-specific skills usually during or immediately after running, often at sprint speed. The quality of the skill performed is likely influenced by the volume of work done in attacking and defending over the duration of the match. Even the most highly skilful players succumb to the impact of fatigue both physical and mental, which may result in underperforming skills at key moments in a match. Fitness is the platform on which skill is performed during team sport. With the onset of fatigue, tired players find it ever more difficult to successfully perform basic skills. Therefore, it is not surprising that teams spend a large proportion of their training time on fitness. While acknowledging the central role of fitness in team sport, the importance of team tactics, underpinned by spatial awareness, must not be neglected. It is well established that a high-carbohydrate diet before a match and, as a supplement during match play, helps delay the onset of fatigue. There is some evidence that players ingesting carbohydrate can maintain sport-relevant skills for the duration of exercise more successfully compared with when ingesting placebo or water. However, most of the assessments of sport-specific skills have been performed in a controlled, non-contested environment. Although these methods may be judged as not ecologically valid, they do rule out the confounding influences of competition on skill performance. The aim of this brief review is to explore whether carbohydrate ingestion, while delaying fatigue during match play, may also help retain sport soccer-specific skill performance.

Exacerbated impairments in neuromuscular function when two bouts of team sport match simulations are separated by 48 h

Intermittent team sports, involving high metabolic and mechanical demands, elicit prolonged impairments in neuromuscular function which persist for ∼48-72 h. Whether impairments in neuromuscular function are exacerbated when such exercise is repeated with incomplete recovery is unknown. This study assessed the neuromuscular, heart rate and metabolic responses to two bouts of ∼90 min modified team sport match simulations separated by 48 h in 12 competitive football players. Before and 2 min after both bouts, knee extensor isometric maximal voluntary contraction (MVC), contractile function (Qtw,pot ) and voluntary activation (VA) were measured. Heart rate (HR), sprint time, blood lactate and glucose were measured throughout both bouts. MVC was reduced relative to baseline at post-bout 1 (21 ± 12%; P = 0.003) and pre-bout 2 (14 ± 11%; P = 0.009), and was lower post-bout 2 (33 ± 14%; P < 0.001) relative to post-bout 1 (P = 0.036). Qtw,pot was reduced post-bout 1 (30 ± 11%; P < 0.001) and pre-bout 2 (9 ± 6%; P = 0.004), and was not different post-bout 2 (28 ± 8%; P < 0.001) relative to post-bout 1 (P = 0.872). VA was reduced post-bout 1 (8 ± 7%; P = 0.023), recovered pre-bout 2 (P = 0.133) and was lower post-bout 2 (16 ± 7%; P < 0.001) relative to post-bout 1 (P = 0.029). Total sprint time was longer, and HR, blood lactate and glucose were lower during bout 2 than bout 1 (P ≤ 0.021). Thus, impairments in neuromuscular function are exacerbated when high-intensity intermittent exercise is performed with incomplete recovery concurrent with accentuated reductions in VA. The lower blood lactate and glucose during the second bout might be due, at least in part, to reduced glycogen availability upon commencing exercise and consequently a greater reliance on glucose extraction. NEW FINDINGS: What is the central question of this study? There is limited evidence on whether impairments in neuromuscular function are exacerbated when prolonged high-intensity intermittent exercise is repeated with incomplete recovery: what are the neuromuscular consequences of performing two bouts of a modified team sport match simulations separated by 48 h? What is the main finding and its importance? Impairments in knee extensor force generating capacity are exacerbated concurrent with accentuated reductions in nervous system activation of muscle when prolonged high-intensity intermittent exercise is repeated with 48 h recovery.

The decision-making in dribbling: a video analysis study of U10 soccer players' skills and coaches' quality evaluation

INTRODUCTION

Dribbling is an important soccer skill that, when effective, allows players to overcome opponents. It can provide a strong tactical advantage; for this reason, all of its components (sprint, speed, and ball control) are fundamental to the development of young players. Dribbling can also be considered a decision-making process, and due to its characteristics, it is not always easy to study ecologically. Using a video analysis study, this research aimed to determine whether dribbling skills, specifically dribbling choice (i.e., decision-making), were related to U10 soccer players' quality.

METHODS

Several outcomes measures, divided into three categories, were taken during video analyses: (i) measures related to the efficacy of dribbling skill; (ii) measures related to the ability of players without the ball to support the player in possession; and (iii) measures related to ball circulation. These data were retrospectively assessed to whether the coaches had formed the teams in training through an implicit knowledge of the players' dribbling skills.

RESULTS

The percentage of accurate dribbling (that is, the ability to perform correct passes after a successful dribble) was found to be the variable that coaches may have implicitly used in creating the three groups differentiated by technical skills (p < 0.05). In fact, this percentage was 12.9%, 24.0%, and 48.1% for the groups with lower, average, and higher technical skills, respectively.

CONCLUSION

Overall, the results demonstrate that dribbling accuracy has an important weight in the coach's evaluation of the technical skills level of young soccer players.

Validity and reliability of the physiological and perceptual responses elicited during a novel treadmill-based Soccer Referee Simulation (SRS)

Purpose

This study explored the validity and reliability of the physiological and perceptual responses elicited during a novel treadmill-based Soccer Referee Simulation (SRS).

Methods

Following the collection of baseline measures and habituation procedures, eight sub-elite soccer referees completed a single trial of the SRS whereby measures of heart rate (HR), oxygen uptake (V̇O2), blood lactate concentrations ([La−]b), and differential ratings of perceived exertion (RPE) were obtained. Referees’ HR responses were also monitored during a series of competitive matches (5 match observations per referee). For the reliability aspect of the investigation, eight well-trained males with soccer playing experience and a comparable physiological profile were initially habituated, and thereafter completed three separate trials of the SRS during which the reliability of the selected outcome variables were ascertained. Trials were separated by 3–7 days and performed under standardised conditions.

Results

No differences were evidenced between the SRS and match play in relation to measures of mean HR (P = 0.444; ES = 0.29), peak HR (P = 0.074; ES = 0.74), or HR-based training impulse (P = 0.498; ES = 0.25). Additionally, no systematic differences were detected between reliability trials for any of the measured outcome variables (P ≥ 0.293), whilst good levels of reliability were observed for measures of mean HR (ICC = 0.94; CV = 3.1%), peak HR (ICC = 0.93; CV = 2.2%), HR-based training impulse (ICC = 0.95; CV = 10.0%), mean V̇O2 (ICC = 0.95; CV = 2.6%); [La−]b (ICC ≥ 0.89; CV ≤ 11.5%), and differential RPE (ICC ≥ 0.94; CV ≤ 15.1%).

Conclusion

The SRS represents a valid and reliable protocol that closely replicates the physiological and decision-making demands of soccer refereeing.

Effects of an intermittent exercise protocol on ankle control during a single-legged landing

Purpose

To identify the effects of fatigue from an exercise protocol (similar to a soccer match) on ankle motion and forces during single-legged drop landing.

Methods

Seventeen males aged (mean ± SD) 22.2 ± 2.0 years participated in this repeated measures study. A 90-min intermittent exercise protocol with a 15-min rest at halftime was performed. Before, at halftime and after the exercise, participants were tested via a single-legged drop landing task onto a force platform whilst wearing a three-dimensional inertial measurement system (Xsens). Ankle angles (plantarflexion/dorsiflexion and inversion/eversion) were analysed before landing and at peak ground reaction force after landing, and center of pressure was analysed at peak ground reaction force.

Results

No significant differences were found for the outcomes between pre-, halftime and post-exercise (p > 0.05).

Conclusions

Findings suggest that exercises simulating a soccer match (regarding exertion) do not necessarily lead to significant changes in ankle motion or forces around the ankle.

A commentary on soccer match-play simulations for applied research and practice

Soccer is a fast-growing area of research, demonstrated by a 10-fold increase in the number of PubMed articles derived from the search term 'soccer' between 2001 and 2021. The scope of contemporary soccer-related articles ranges from match-play observations to laboratory evaluations of performance. The activity profile of soccer match-play is variable and techniques to collect data within matches are limited. Soccer-specific simulations have been developed to simulate the evolving demands of match-play. The evolutionary designs of novel simulations provide a reproducible exercise stimulus for varying researcher and practitioner objectives. The applied researcher can utilise simulations to investigate the efficacy of nutritional interventions and environmental stress on performance, while assessing the physiological and biomechanical responses to representations of match-play. Practitioners can adopt simulations for rehabilitation to progressively facilitate return-to-play processes, while implementing extra top-up conditioning sessions for unused and partial-match players. However, there are complexities involved with the selection of varying simulations which are dependent on the research question or practical application. There also remains a paucity of published information to support researchers and practitioners in selecting from differing simulation models. To assist with researcher and practitioner interpretations, we present a commentary of the current simulations to inform decision-making processes for research and training purposes and enhance the application of future research. An objective scoring system was adopted for rating the research and practical applications of each simulation design. Overall scores of 22, 16 and 18 out of 36 were revealed for free-running (n=7), non-motorised- (n=4) and motorised-treadmill-based simulations (n=4), respectively.

The influence of playing surface on external demands and physiological responses during a soccer match simulation

We investigated the effects of playing surfaces with different impact absorption characteristics on external demand and physiological responses. Fifteen participants completed a soccer match simulation on natural grass, synthetic turf and concrete surfaces. Accelerometry-derived PlayerLoad^TM per minute (PL·min^-1) and average net force (AvF_Net) were used to quantify external demands at the centre of mass (CoM), upper-back, mid-back and hip. Heart rate, oxygen uptake, energy expenditure and RPE quantified physiological responses. The concrete surface exhibited the least impact absorption, with peak decelerations ~3.5x synthetic turf and ~10x natural grass (p < 0.001). Despite this, there was no differences in external demand between surfaces (surface: p ≥ 0.194; η²_p≤0.092). Both AvF_Net and PL·min^-1 (location: p < 0.001; η²_p≥0.859) were higher at the hip (613(91)N; 12.5(1.2)arb.u), reduced at the mid-back (521(67)N; 8.8(0.7)arb.u) and upper-back (502(60)N; 8.8(0.7)arb.u) when compared to CoM (576(78)N; 10.7(1.0)arb.u). Although playing surface did not influence the external demands, heart rate or oxygen uptake (p > 0.05), energy expenditure was highest on natural grass compared to synthetic turf (P = 0.034) and RPE was highest on synthetic turf compared to concrete (p = 0.026). Different playing surfaces can alter physiological responses to soccer-specific activity even when the external demands are similar.

Weekly Variations of Short-Duration Maximal Jumping Performance in Soccer Players: Exploring Relationships With Accumulated Training Load and Match Demands

Purpose: The aim of this study was 2-fold: (1) to analyze variations of short-duration maximal jumping performance in players exposed to a match and those who were not and (2) to analyze the relationships between changes in the short-duration maximal jumping performance and different accumulated training load and match demands measures.

Methods: Twenty-four professional soccer players (age: 20.3 ± 1.7 years) were monitored daily for their training load and match demands over 6 weeks. In addition, they performed a weekly short-duration maximal jumping performance test (72 h after the last match).

Results: Negative moderate correlations were found between percentage of change of countermovement jump (CMJ) height and Acummulated training load (ATL) of total distance (TD), high metabolic load (HML), accelerations (ACC), and decelerations (DEC) (r = −0.38, p = 0.004; r = −0.33, p = 0.013; r = −0.39, p = 0.003; and r = −0.30, p = 0.026). No correlations were found for match load (ML). TD, HML, ACC, and DCC (r = 0.27, r = 0.25, r = 0.31, and r = 0.22, respectively) were used to predict the percentage of change of CMJ height.

Conclusion: Match participation has negative effects on CMJ performance. The ATL of HML, ACC, DCC, and TD have a significant influence on both CMJ measures changes. Also, the ATL values of those metrics are the best predictors of the percentage changes of CMJ performance.

Acute Effects of Warm-Up, Exercise and Recovery-Related Strategies on Assessments of Soccer Kicking Performance: A Critical and Systematic Review

BACKGROUND

A number of reviews have collated information on the impact of warming-up, physical exertion and recovery strategies on physical, subjective and physiological markers in soccer players yet none have solely analyzed their potential effects on components of kicking performance.

OBJECTIVE

To systematically analyse the influence of warm-up, exercise and/or recovery-related strategies on kicking performance in male soccer players and provide a critical appraisal on research paradigm related to kicking testing constraints and data acquisition methods.

METHODS

A systematic literature search was performed (until July 2020) in PubMed, Web of Science, SPORTDiscus, Scopus and ProQuest. Studies in male soccer populations, which included the effects of warm-up routines, physical exercise and/or recovery-related interventions, reported on comparisons pre-post or between experimental conditions and that computed at least one measure of kicking kinematics and/or performance were considered. Methodological quality and risk of bias were determined for the included studies. Constraints related to kicking testing and data acquisition methods were also summarized and discussed.

RESULTS

Altogether, 52 studies were included. Of these, 10 examined the respective effects of a warm-up, 34 physical exercise, and 21 recovery-related strategies. The results of eight studies showed that lower limb kinematics, kicking accuracy or ball velocity were improved following warm-ups involving dynamic but not static stretching. Declines in ball velocity occurred notably following intermittent endurance or graded until exhaustion exercise (three studies in both cases) without inclusion of any ball skills. In contrast, conflicting evidence in five studies was observed regarding ball velocity following intermittent endurance exercise interspersed with execution of ball skills. Kicking accuracy was less frequently affected by physical exercise (remained stable across 14 of 19 studies). One investigation indicated that consumption of a carbohydrate beverage pre- and mid-exercise demonstrated benefits in counteracting the potentially deleterious consequences of exercise on ball velocity, while four studies reported conflicting results regarding kicking accuracy. Most evidence synthesized for the interventions demonstrated moderate level (77%) and unclear-to-high risk of bias in at least one item evaluated (98%). The main limitations identified across studies were kicks generally performed over short distances (50%), in the absence of opposition (96%), and following experimental instructions which did not concomitantly consider velocity and accuracy (62%). Also, notational-based metrics were predominantly used to obtain accuracy outcomes (54%).

CONCLUSIONS

The results from this review can help inform future research and practical interventions in an attempt to measure and optimise soccer kicking performance. However, given the risk of bias and a relative lack of strong evidence, caution is required when applying some of the current findings in practice.

PROSPERO ID

CRD42018096942.

Physical performance and perception of foot discomfort during a soccer-specific match simulation. A comparison of football boots

Football boots are marketed with emphasis on a single key performance characteristic (e.g. speed). Little is known on how design parameters impact players' performance. This study investigated the impact of boot design on performance maintenance and perceived foot comfort during a 90-minute match simulation drill. Eleven male university football players tested two commercially available "sprint boots" known to generate significantly different plantar pressures (high=Boot H and low=Boot L) . Players completed a modified Soccer-specific Aerobic Field Test on a 3G pitch. Heart rate, rated perceived exertion and perceived foot discomfort were assessed for each 15-min interval. Power generation was assessed pre- and post-match simulation. A significantly higher mean heart rate was seen for Boot L in the 60th-75th and 75th-90th minute intervals (P = 0.017, P = 0.012 respectively). Perceived exertion did not differ between boots (P ≥ 0.302). Power generation significantly decreased in Boot H between pre- and post-match (P = 0.042). Both boots increased discomfort with significantly more plantar discomfort felt in the last 30 min in Boot H (75th min: P = 0.037; 90th min: P = 0.048). The results imply that a comfortable boot design may improve maintenance of performance during match-play.

Development of a Twenty20 Field-Based Simulation for Cricket Fast Bowlers (FBS-T20)

ABSTRACT

Milne, EC, Vickery, WM, Dascombe, BJ, and Borges, NR. Development of a twenty20 field-based simulation for cricket fast bowlers (FBS-T20). J Strength Cond Res XX(X): 000-000, 2020-This project assessed the validity and reliability of a novel Twenty20 cricket pace bowling simulation (FBS-T20) that could be used to facilitate match-specific testing and training outside of match play. Six recreational pace bowlers completed 3 identical sessions of the FBS-T20. The FBS-T20 consisted of 4 bowling and 16 fielding overs. During the bowling overs, a bowling accuracy test and bowling approach speed were measured, whereas during the fielding overs, 10-m sprint performance was assessed. Distance covered, heart rate (HR), and rating of perceived exertion (RPE) were also collected throughout the FBS-T20. Validity was determined through comparison with previously reported Twenty20 pace bowling match demands, and intersession reliabilities were assessed. Distances covered in speed zones were valid (p > 0.05) with the exception of significantly lower jog values in the FBS-T20 (957-1,279 vs. 2,195 m; p = 0.04-<0.001). The maximal HR was found to be valid, but the mean HR was significantly higher than previously published data (147-151 bpm vs. 133 bpm; p = 0.014-0.003). Distances covered demonstrated high levels of reliability, with increasing reliability found after additional sessions (coefficient of variation [CV]% = 3.8-14.4). The HR (CV% = 4.8-6.3) and session RPE (CV% = 10.8) demonstrated moderate reliability, whereas approach speed, 10-m sprint, and bowling skills test results possessed low levels of reliability. The FBS-T20 is a practically viable testing and training tool that is valid and reliable for distances covered at high speeds. One full familiarization session is recommended for optimal reliability.

Body temperature and physical performance responses are not maintained at the time of pitch-entry when typical substitute-specific match-day practices are adopted before simulated soccer match-play

OBJECTIVES

To profile performance and physiological responses to typical patterns of match-day activity for second-half soccer substitutes.

DESIGN

Descriptive.

METHODS

Following a warm-up, 13 male team sports players underwent ∼85min of rest, punctuated with five min rewarm-ups at ∼25, ∼50, and ∼70min, before ∼30min of simulated soccer match-play. Countermovement jump performance (jump height, peak power output), alongside 15m sprints, were assessed post-warm-up, and pre- and post-simulated match-play. Core temperature, heart rate, ratings of perceived exertion, and blood glucose and lactate concentrations were measured throughout.

RESULTS

Warm-up-induced core temperature elevations (∼2.3%, +0.85°C; p<0.001) were maintained until after the first rewarm-up. Thereafter, core temperature was reduced from post-warm-up values until pre-simulated match-play (∼1.6%, -0.60°C; p<0.001), where values were similar to pre-warm-up (37.07±0.24°C, p=0.981). Simulated match-play increased core temperature progressively (p≤0.05) but values remained lower than post-warm-up (∼5min; p=0.002) until ∼10min into exercise. From post-warm-up to pre-simulated match-play, sprint times (∼3.9%, +0.10s, p=0.003), jump height (∼9.4%, -3.1cm; p=0.017), and peak power output (∼7.2%, -296W; p<0.001) worsened. Despite increased ratings of perceived exertion and elevated blood lactate concentrations (p≤0.05), sprint times were maintained throughout exercise, whereas peak power increased (∼7.8%, +294W; p=0.006) pre- to post-exercise.

CONCLUSIONS

At the point of simulated pitch-entry, body temperature and physical performance responses were not maintained from warm-up cessation despite typical substitute-specific match-day practices being employed in thermoneutral conditions. Evidence of performance-limiting fatigue was absent during ∼30min of simulated match-play. These data question the efficacy of practices typically implemented by substitutes before pitch-entry.

Biomechanical and Physiological Responses to 120 Min. of Soccer-Specific Exercise

Purpose: The purpose of the study is to investigate biomechanical and physiological responses to soccer-specific exercise incorporating an extra-time period (ET) and assess the test-retest reliability of these responses. Methods: Twelve soccer players performed 120 min of soccer-specific exercise. Tri-axial (PL_Total) and uni-axial PlayerLoad™ in the vertical (PL_V), anterior-posterior (PL_A-P), and medial-lateral (PL_M-L) planes were monitored using a portable accelerometer. Likewise, respiratory exchange ratio (RER) was recorded throughout exercise. At the end of each 15-min period, players provided differential ratings of perceived exertion for legs (RPE-L), breathlessness (RPE-B) and overall (RPE-O), and capillary samples were taken to measure blood lactate (BLa) concentrations. The soccer-specific exercise was completed twice within 7 days to assess reliability. Results: A main effect for time was identified for PL_Total (p = 0.045), PL_V (p = 0.002), PL_A-P (p = 0.011), RER (p = 0.001), RPE-L (p = 0.001), RPE-O (p = 0.003), and CMJ (p = 0.020). A significant increase in PL_Total (234 ± 34 au) and decrease in RER (0.87 ± 0.03) was evident during 105-120 versus 0-15 min (215 ± 25 au; p = 0.002 and 0.92 ± 0.02; p = 0.001). Coefficients of variations were <10% and Pearson's correlation coefficient demonstrated moderate-to-very strong (0.33-0.99) reliability for all PL variables, RPE-B, BLa, and RER. Conclusions: These results suggest that mechanical efficiency is compromised and an increased rate of lipolysis is observed as a function of exercise duration, particularly during ET. These data have implications for practitioners interested in fatigue-induced changes during ET.

Match-Play and Performance Test Responses of Soccer Goalkeepers: A Review of Current Literature

Goalkeepers are typically the last defensive line for soccer teams aiming to minimise goals being conceded, with match rules permitting ball handling within a specific area. Goalkeepers are also involved in initiating some offensive plays, and typically remain in close proximity to the goal line while covering ~ 50% of the match distances of outfield players; hence, the competitive and training demands of goalkeepers are unique to their specialised position. Indeed, isolated performance tests differentiate goalkeepers from outfield players in multiple variables. With a view to informing future research, this review summarised currently available literature reporting goalkeeper responses to: (1) match play (movement and skilled/technical demands) and (2) isolated performance assessments (strength, power, speed, aerobic capacity, joint range of motion). Literature searching and screening processes yielded 26 eligible records and highlighted that goalkeepers covered ~ 4-6 km on match day whilst spending ~ 98% of time at low-movement intensities. The most decisive moments are the 2-10 saves·match^-1 performed, which often involve explosive actions (e.g. dives, jumps). Whilst no between-half performance decrements have been observed in professional goalkeepers, possible transient changes over shorter match epochs remain unclear. Isolated performance tests confirm divergent profiles between goalkeepers and outfield players (i.e. superior jump performance, reduced [Formula: see text]_2max values, slower sprint times), and the training of soccer goalkeepers is typically completed separately from outfield positions with a focus primarily on technical or explosive drills performed within confined spaces. Additional work is needed to examine the physiological responses to goalkeeper-specific training and match activities to determine the efficacy of current preparatory strategies.

Profiling the Responses of Soccer Substitutes: A Review of Current Literature

Depending upon competition regulations, the laws of soccer allow between three and an unlimited number of substitutions that can be made on either a permanent or rolling basis. Substitutes are typically introduced to minimise/offset the effects of fatigue, alter tactics, replace players deemed as underperforming or injured, and/or give playing time to youth players or to squad members returning from injury. While the match-day practices of substitutes include participation in the pre-match warm-up, and sporadic periods of rewarm-up activity, it is currently unclear as to whether these pre-entry preparations facilitate optimal match performance thereafter. Acknowledging the contextual factors that possibly influence substitutes' performance, this review summarises the presently available literature on soccer substitutes, and makes recommendations for future research. Literature searching and screening yielded 13 studies, which have typically focused on characterising: (1) the patterns, including timing, of substitutes' introduction; (2) indices of match-performance; and (3) the emotional experiences of soccer substitutes. The majority of substitutions occur after the first-half has ended (i.e. at half-time or during the second-half), with introduced players exceeding the second-half physical performances of those who started the match. Observations of progressive improvements in running performance as playing time increases, and findings that substitutes mostly experience negative emotions, highlight the potential inadequacies of pre-match preparations, and present future research opportunities. Additional work is therefore needed to confirm these findings and to determine the efficacy of current preparation strategies, thereby providing opportunities to assess then address substitutes' pre-pitch entry preparations, on-field performance and emotional responses.

A match-day analysis of the movement profiles of substitutes from a professional soccer club before and after pitch-entry

Whilst the movement demands of players completing a whole soccer match have been well-documented, comparable information relating to substitutes is sparse. Therefore, this study profiled the match-day physical activities performed by soccer substitutes, focusing separately on the pre and post pitch-entry periods. Seventeen English Championship soccer players were monitored using 10 Hz Micromechanical Electrical Systems (MEMS) devices during 13 matches in which they participated as substitutes (35 observations). Twenty physical variables were examined and data were organised by bouts of warm-up activity (pre pitch-entry), and five min epochs of match-play (post pitch-entry). Linear mixed modelling assessed the influence of time (i.e., ‘bout’ and ‘epoch’), playing position, and match scoreline. Substitutes performed 3±1 rewarm-up bouts∙player^-1∙match^-1. Compared to the initial warm-up, each rewarm-up was shorter (-19.7 to -22.9 min) and elicited less distance (-606 to -741 m), whilst relative total distances were higher (+26 to +69 m∙min^-1). Relative total (+13.4 m∙min^-1) and high-speed (+0.4 m∙min^-1) distances covered during rewarm-ups increased (p <0.001) with proximity to pitch-entry. Players covered more (+3.2 m; p = 0.047) high-speed distance per rewarm-up when the assessed team was losing compared with when winning at the time of pitch-entry. For 10 out of 20 variables measured after pitch-entry, values reduced from 0–5 min thereafter, and substitutes covered greater (p ˂0.05) total (+67 to +93 m) and high-speed (+14 to +33 m) distances during the first five min of match-play versus all subsequent epochs. Midfielders covered more distance (+41 m) per five min epoch than both attackers (p ˂0.001) and defenders (p = 0.016). Acknowledging the limitations of a solely movement data approach and the potential influence of other match-specific factors, such findings provide novel insights into the match-day demands faced by substitute soccer players. Future research opportunities exist to better understand the match-day practices of this population.

Acute and Residual Soccer Match-Related Fatigue: A Systematic Review and Meta-analysis

BACKGROUND

Understanding soccer players' match-related fatigue and recovery profiles likely helps with developing conditioning programs that increase team performance and reduce injuries and illnesses. In order to improve match recovery (the return-to-play process and ergogenic interventions) it is also pivotal to determine if match simulation protocols and actual match-play lead to similar responses.

OBJECTIVES

(1) To thoroughly describe the development of fatigue during actual soccer match play and its recovery time course in terms of physiological, neuromuscular, technical, biochemical and perceptual responses, and (2) to determine similarities of recovery responses between actual competition (11 vs. 11) and match simulations.

METHODS

A first screening phase consisted of a systematic search on PubMed (MEDLINE) and SportDiscus databases until March 2016. Inclusion criteria were: longitudinal study with soccer players; match or validated protocol; duration > 45 min; and published in English.

RESULTS

A total of 77 eligible studies (n = 1105) were used to compute 1196 effect sizes (ES). Half-time assessments revealed small to large alterations in immunological parameters (e.g. leukocytes, ES = 1.9), a moderate decrement in insulin concentration (ES = - 0.9) and a small to moderate impairment in lower-limb muscle function (ES = - 0.5 to - 0.7) and physical performance measures (e.g. linear sprint, ES = - 0.3 to - 1.0). All the systematically analyzed fatigue-related markers were substantially altered at post-match. Hamstrings force production capacity (ES = - 0.7), physical performance (2-4%, ES = 0.3-0.5), creatine kinase (CK, ES = 0.4), well-being (ES = 0.2-0.4) and delayed onset muscle soreness (DOMS, ES = 0.6-1.3) remained substantially impaired at G + 72 h. Compared to simulation protocols, 11 vs. 11 match format (CK, ES = 1.8) induced a greater magnitude of change in muscle damage (i.e. CK, ES = 1.8 vs. 0.7), inflammatory (IL-6, ES = 2.6 vs. 1.1) and immunological markers and DOMS (ES = 1.5 vs. 0.7) than simulation protocols at post-assessments. Neuromuscular performances at post-match did not differ between protocols.

CONCLUSION

While some parameters are fully recovered (e.g. hormonal and technical), our systematic review shows that a period of 72 h post-match play is not long enough to completely restore homeostatic balance (e.g. muscle damage, physical and well-being status). The extent of the recovery period post-soccer game cannot consist of a 'one size fits all approach'. Additionally, the 'real match' (11 vs. 11 format) likely induces greater magnitudes of perceptual (DOMS) and biochemical alterations (e.g. muscle damage), while neuromuscular alterations were essentially similar. Overall, coaches must adjust the structure and content of the training sessions during the 72-h post-match intervention to effectively manage the training load within this time-frame.

Temporal changes in physiological and performance responses across game-specific simulated basketball activity

PURPOSE

The aims of this study were to: (1) provide a comprehensive physiological profile of simulated basketball activity and (2) identify temporal changes in player responses in controlled settings.

METHODS

State-level male basketball players (n = 10) completed 4 × 10 min simulated quarters of basketball activity using a reliable and valid court-based test. A range of physiological (ratings of perceived exertion, blood lactate concentration ([BLa-]), blood glucose concentration ([BGlu]), heart rate (HR), and hydration) and physical (performance and fatigue indicators for sprint, circuit, and jump activity) measures were collected across testing.

RESULTS

Significantly reduced [BLa-] (6.19 ± 2.30 vs. 4.57 ± 2.33 mmol/L; p = 0.016) and [BGlu] (6.91 ± 1.57 vs. 5.25 ± 0.81 mmol/L; p = 0.009) were evident in the second half. A mean HR of 180.1 ± 5.7 beats/min (90.8% ± 4.0% HRmax) was observed, with a significant increase in vigorous activity (77%-95% HRmax) (11.31 ± 6.91 vs. 13.50 ± 6.75 min; p = 0.024) and moderate decrease in near-maximal activity (>95% HRmax) (7.24 ± 7.45 vs. 5.01 ± 7.20 min) in the second half. Small increases in performance times accompanied by a significantly lower circuit decrement (11.67% ± 5.55% vs. 7.30% ± 2.16%; p = 0.032) were apparent in the second half.

CONCLUSION

These data indicate basketball activity imposes higher physiological demands than previously thought and temporal changes in responses might be due to adapted pacing strategies as well as fatigue-mediated mechanisms.

Carbohydrates for Soccer: A Focus on Skilled Actions and Half-Time Practices

Carbohydrate consumption is synonymous with soccer performance due to the established effects on endogenous energy store preservation, and physical capacity maintenance. For performance-enhancement purposes, exogenous energy consumption (in the form of drinks, bars, gels and snacks) is recommended on match-day; specifically, before and during match-play. Akin to the demands of soccer, limited opportunities exist to consume carbohydrates outside of scheduled breaks in competition, such as at half-time. The link between cognitive function and blood glucose availability suggests that carbohydrates may influence decision-making and technical proficiency (e.g., soccer skills). However, relatively few reviews have focused on technical, as opposed to physical, performance while also addressing the practicalities associated with carbohydrate consumption when limited in-play feeding opportunities exist. Transient physiological responses associated with reductions in activity prevalent in scheduled intra-match breaks (e.g., half-time) likely have important consequences for practitioners aiming to optimize match-day performance. Accordingly, this review evaluated novel developments in soccer literature regarding (1) the ergogenic properties of carbohydrates for skill performance; and (2) novel considerations concerning exogenous energy provision during half-time. Recommendations are made to modify half-time practices in an aim to enhance subsequent performance. Viable future research opportunities exist regarding a deeper insight into carbohydrate provision on match-day.

A comparison of isomaltulose versus maltodextrin ingestion during soccer-specific exercise

Purpose

The performance and physiological effects of isomaltulose and maltodextrin consumed intermittently during prolonged soccer-specific exercise were investigated.

Methods

University soccer players (n = 22) performed 120 min of intermittent exercise while consuming 8% carbohydrate–electrolyte drinks (equivalent to ~ 20 g h⁻¹) containing maltodextrin (Glycaemic Index: 90–100), isomaltulose (Glycaemic Index: 32) or a carbohydrate-energy-free placebo in a manner replicating the practices of soccer players (i.e., during warm-up and half-time). Physical (sprinting, jumping) and technical (shooting, dribbling) performance was assessed.

Results

Blood glucose and plasma insulin (both P < 0.001) concentrations varied by trial with isomaltulose maintaining > 13% higher blood glucose concentrations between 75 and 90 min versus maltodextrin (P < 0.05). A decline in glycaemia at 60 min in maltodextrin was attenuated with isomaltulose (−19 versus −4%; P = 0.015). Carbohydrates attenuated elevations in plasma epinephrine concentrations (P < 0.05), but isomaltulose proved most effective at 90 and 120 min. Carbohydrates did not attenuate IL-6 increases or reductions in physical or technical performances (all P > 0.05). Ratings of abdominal discomfort were influenced by trial (P < 0.05) with lower values for both carbohydrates compared to PLA from 60 min onwards.

Conclusions

Although carbohydrates (~ 20 g h⁻¹) did not attenuate performance reductions throughout prolonged soccer-specific exercise, isomaltulose maintained higher blood glucose at 75–90 min, lessened the magnitude of the exercise-induced rebound glycaemic response and attenuated epinephrine increases whilst maintaining similar abdominal discomfort values relative to maltodextrin. When limited opportunities exist to consume carbohydrates on competition-day, low-glycaemic isomaltulose may offer an alternative nutritional strategy for exercising soccer players.

Predictors of Linear and Multidirectional Acceleration in Elite Soccer Players

Jonathan, N, Russell, M, Shearer, D, Cook, CJ, and Kilduff, LP. Predictors of linear and multidirectional acceleration in elite soccer players. J Strength Cond Res 33(2): 514-522, 2019-Linear and multidirectional acceleration underpins success in professional soccer match play. However, the physical qualities that determine these performance indicators are poorly understood in elite players. English Premier League players (n = 26) performed isometric midthigh pulls (IMTPs), bilateral and unilateral drop jumps (from 40 and 20 cm, respectively), bilateral and unilateral countermovement jumps (CMJs), and assessments of linear (5, 10, and 20 m) and multidirectional (left and right preplanned and reactive) acceleration. Regression analyses highlighted that 21% of variance in 5-m sprint time (1.02 ± 0.07 seconds) was explained by relative peak power output (PPO) in bilateral CMJ (54.5 ± 5.3 W·kg). A 5.4 W·kg increase in CMJ predicted a 0.03-second decrease in 5-m sprint time (P = 0.02). For 10-m sprint time (1.72 ± 0.09 seconds), 44% of variance was explained by isometric relative peak force ([PF]; 30.4 ± 4.9 N·kg) and bilateral relative CMJ PPO (54.5 ± 5.3 W·kg). A 5.4 W·kg increase in CMJ predicted reduced 10-m sprint times by 0.04 seconds (P = 0.01). For 20-m sprint time (2.94 ± 0.11 seconds), 55% of the total variance was explained by isometric relative PF (30.4 ± 4.9 N·kg) and relative CMJ PPO (54.5 ± 5.3 W·kg). Increases of 5.4 W·kg in bilateral CMJ predicted an improvement of 20-m sprint time by 0.06 seconds (P = 0.002). Contributions were insignificant (P > 0.05) for preplanned and reactive multidirectional acceleration. Relativized indices, especially those related to force production during CMJ and IMTP tests, likely underpin linear but not multidirectional acceleration performance in professional soccer players. When linear acceleration is a training focus, practitioners should seek to monitor CMJ and IMTP test performance.

Changes in Acceleration and Deceleration Capacity Throughout Professional Soccer Match-Play

Russell, M, Sparkes, W, Northeast, J, Cook, CJ, Love, TD, Bracken, RM, and Kilduff, LP. Changes in acceleration and deceleration capacity throughout professional soccer match-play. J Strength Cond Res 30(10): 2839-2844, 2016-As the acceleration and deceleration demands of soccer are currently not well understood, this study aimed to profile markers of acceleration and deceleration capacity during professional soccer match-play. This within-player observational study required reserve team players from a Premier League club to wear 10-Hz Global Positioning System units throughout competitive matches played in the 2013-14 competitive season. Data are presented for players who completed 4 or more games during the season (n = 11), and variables are presented according to six 15-minute intervals (I1-6: 00:00-14:59 minutes, 15:00-29:59 minutes, 30:00-44:59 minutes, 45:00-59:59 minutes, 60:00-74:59 minutes, and 75:00-89:59 minutes, respectively). During I6, the distance covered (total, per minute, and at high intensity), number of sprints, accelerations (total and high intensity), decelerations (total and high intensity), and impacts were reduced compared with I1 (all p ≤ 0.05). The number of high-intensity impacts remained unchanged throughout match-play (p > 0.05). These findings indicate that high-intensity actions and markers of acceleration and deceleration capacity are reduced in the last 15 minutes of the normal duration of match-play. Such information can be used to increase the specificity of training programs designed for soccer players while also giving further insight in to the effects of 90 minutes of soccer-specific exercise. Interventions that seek to maintain the acceleration and deceleration capacity of players throughout the full duration of a soccer match warrant investigation.

Motion Analysis of Match Play in New Zealand U13 to U15 Age-Group Soccer Players

Atan, SA, Foskett, A, and Ali, A. Motion analysis of match play in New Zealand U13 to U15 age-group soccer players. J Strength Cond Res 30(9): 2416-2423, 2016-The purpose of this study was to investigate motion analysis in 85 players (U13-U15 years) from Auckland's Metropolitan League during 2 competitive soccer matches. Five-Hz global positioning system (with interpolated 10-Hz output) units were used to measure total distance (absolute and relative) and time spent in standing, walking, low-intensity running, medium-intensity running, high-intensity running, and sprinting. Speed thresholds for each match activity were determined through mean 10-m flying sprint peak speed for each age group. Under 15 years (U15, 6600 ± 1480 m) covered more absolute distance because of longer playing time than under 14 years (U14, 5385 ± 1296 m, p = 0.001) and under 13 years (U13, 4516 ± 702.6 m, p = 0.001). However, there were no differences in relative distances covered (U15, 94.5 ± 11.2 m·min, U14, 96.1 ± 11.9 m·min, U15, 97.3 ± 17.6 m·min, p = 0.685). Maximum speed attained during the match was faster for U15 (26.5 ± 1.68 km·h) than U14 (25.4 ± 1.93 km·h, p = 0.022) and U13 (23.5 ± 1.74 km·h, p = 0.001); there were no differences in average distance per sprint, with all age groups covering ∼16 m per sprint (p = 0.603). The current findings provide useful information for developing specific training programs for young soccer players and a framework for developing age-specific soccer simulation protocols.

Between-Match Variability of Peak Power Output and Creatine Kinase Responses to Soccer Match-Play

Post-match assessments of peak power output (PPO) during countermovement jumps and creatine kinase (CK) concentrations are common markers of recovery status in soccer players. Yet, the impact of soccer match-play on recovery in the 48 hours after competition is unclear, and the between-match variability of these responses has not been examined. Fourteen reserve team players from an English Premier League club were examined over 1-4 matches per player. Creatine kinase and PPO were measured before, 24, and 48 hours after each match. Data were analyzed with within-subjects linear mixed models. Compared with the prematch baseline, PPO was 237 ± 170 W and 98 ± 168 W lower at 24 and 48 hours, respectively (p ≤ 0.005) and CK was elevated (24 hours: 334.8 ± 107.2 μ·L(-1), 48 hours: 156.9 ± 121.0 μ·L(-1); both p ≤ 0.001) after match-play. These responses were consistent across the different matches and playing positions (p > 0.05). Within-subject correlations between PPO and CK were significant (r = -0.558; p ≤ 0.005). The between-match variability of PPO was 10.9, 11.0, and 9.9%, respectively at baseline, 24 and 48 hours, whereas for CK, the variability was 41.7, 30.0, and 34.3%, respectively. These findings highlight that more than 48 hours are needed to restore metabolic and performance perturbations after soccer match-play, and that CK demonstrates greater between-match variability than PPO. Such information is likely to be of interest to those responsible for the design of training schedules in the days after a match and sports scientists whose responsibilities include the monitoring of recovery status in soccer players.

Carbohydrate Nutrition and Team Sport Performance

The common pattern of play in 'team sports' is 'stop and go', i.e. where players perform repeated bouts of brief high-intensity exercise punctuated by lower intensity activity. Sprints are generally 2-4 s long and recovery between sprints is of variable length. Energy production during brief sprints is derived from the degradation of intra-muscular phosphocreatine and glycogen (anaerobic metabolism). Prolonged periods of multiple sprints drain muscle glycogen stores, leading to a decrease in power output and a reduction in general work rate during training and competition. The impact of dietary carbohydrate interventions on team sport performance have been typically assessed using intermittent variable-speed shuttle running over a distance of 20 m. This method has evolved to include specific work to rest ratios and skills specific to team sports such as soccer, rugby and basketball. Increasing liver and muscle carbohydrate stores before sports helps delay the onset of fatigue during prolonged intermittent variable-speed running. Carbohydrate intake during exercise, typically ingested as carbohydrate-electrolyte solutions, is also associated with improved performance. The mechanisms responsible are likely to be the availability of carbohydrate as a substrate for central and peripheral functions. Variable-speed running in hot environments is limited by the degree of hyperthermia before muscle glycogen availability becomes a significant contributor to the onset of fatigue. Finally, ingesting carbohydrate immediately after training and competition will rapidly recover liver and muscle glycogen stores.

Acute Effects of Carbohydrate Supplementation on Intermittent Sports Performance

Intermittent sports (e.g., team sports) are diverse in their rules and regulations but similar in the pattern of play; that is, intermittent high-intensity movements and the execution of sport-specific skills over a prolonged period of time (~1–2 h). Performance during intermittent sports is dependent upon a combination of anaerobic and aerobic energy systems, both of which rely on muscle glycogen and/or blood glucose as an important substrate for energy production. The aims of this paper are to review: (1) potential biological mechanisms by which carbohydrate may impact intermittent sport performance; (2) the acute effects of carbohydrate ingestion on intermittent sport performance, including intermittent high-intensity exercise capacity, sprinting, jumping, skill, change of direction speed, and cognition; and (3) what recommendations can be derived for carbohydrate intake before/during exercise in intermittent sports based on the available evidence. The most researched intermittent sport is soccer but some sport-specific studies have also been conducted in other sports (e.g., rugby, field hockey, basketball, American football, and racquet sports). Carbohydrate ingestion before/during exercise has been shown in most studies to enhance intermittent high-intensity exercise capacity. However, studies have shown mixed results with regards to the acute effects of carbohydrate intake on sprinting, jumping, skill, change of direction speed, and cognition. In most of these studies the amount of carbohydrate consumed was ~30–60 g/h in the form of a 6%–7% carbohydrate solution comprised of sucrose, glucose, and/or maltodextrin. The magnitude of the impact that carbohydrate ingestion has on intermittent sport performance is likely dependent on the carbohydrate status of the individual; that is, carbohydrate ingestion has the greatest impact on performance under circumstances eliciting fatigue and/or hypoglycemia. Accordingly, carbohydrate ingestion before and during a game seems to have the greatest impact on intermittent sports performance towards the end of the game.

Physiological and performance effects of carbohydrate gels consumed prior to the extra-time period of prolonged simulated soccer match-play

OBJECTIVES

The physiological and performance effects of carbohydrate-electrolyte gels consumed before the 30min extra-time period of prolonged soccer-specific exercise were investigated.

DESIGN

Randomised, double-blind, crossover.

METHODS

Eight English Premier League academy soccer players performed 120min of soccer-specific exercise on two occasions while consuming fluid-electrolyte beverages before exercise, at half-time and 90min. Carbohydrate-electrolyte (0.7±0.1gkg(-1) BM) or energy-free placebo gels were consumed ∼5min before extra-time. Blood samples were taken before exercise, at half-time and every 15min during exercise. Physical (15-m and 30-m sprint speed, 30-m sprint maintenance and countermovement jump height) and technical (soccer dribbling) performance was assessed throughout each trial.

RESULTS

Carbohydrate-electrolyte gels improved dribbling precision (+29±20%) and raised blood glucose concentrations by 0.7±0.8mmoll(-1) during extra-time (both p<0.01). Supplementation did not affect sprint velocities (15m and 30m), 30-m sprint maintenance or dribbling speed as reductions compared to 0-15min values occurred at 105-120min irrespective of trial (all p<0.05). Plasma osmolality and blood sodium concentrations increased post-exercise vs. the opening 15min (p<0.05) but no effect of supplementation existed. Selected markers of physical performance (jump height, 30-m sprint velocity and 30-m repeated sprint maintenance) also reduced by >3% during half-time (all p<0.05).

CONCLUSIONS

Carbohydrate-electrolyte gel ingestion raised blood glucose concentrations and improved dribbling performance during the extra-time period of simulated soccer match-play. Supplementation did not attenuate reductions in physical performance and hydration status that occurred during extra-time.

A passive heat maintenance strategy implemented during a simulated half-time improves lower body power output and repeated sprint ability in professional Rugby Union players

Reduced physical performance has been observed following the half-time period in team sports players, likely due to a decrease in muscle temperature during this period. We examined the effects of a passive heat maintenance strategy employed between successive exercise bouts on core temperature (T_core) and subsequent exercise performance. Eighteen professional Rugby Union players completed this randomised and counter-balanced study. After a standardised warm-up (WU) and 15 min of rest, players completed a repeated sprint test (RSSA 1) and countermovement jumps (CMJ). Thereafter, in normal training attire (Control) or a survival jacket (Passive), players rested for a further 15 min (simulating a typical half-time) before performing a second RSSA (RSSA 2) and CMJ’s. Measurements of T_core were taken at baseline, post-WU, pre-RSSA 1, post-RSSA 1 and pre-RSSA 2. Peak power output (PPO) and repeated sprint ability was assessed before and after the simulated half-time. Similar T_core responses were observed between conditions at baseline (Control: 37.06±0.05°C; Passive: 37.03±0.05°C) and for all other T_core measurements taken before half-time. After the simulated half-time, the decline in T_core was lower (-0.74±0.08% vs. -1.54±0.06%, p<0.001) and PPO was higher (5610±105 W vs. 5440±105 W, p<0.001) in the Passive versus Control condition. The decline in PPO over half-time was related to the decline in T_core (r = 0.632, p = 0.005). In RSSA 2, best, mean and total sprint times were 1.39±0.17% (p<0.001), 0.55±0.06% (p<0.001) and 0.55±0.06% (p<0.001) faster for Passive versus Control. Passive heat maintenance reduced declines in T_core that were observed during a simulated half-time period and improved subsequent PPO and repeated sprint ability in professional Rugby Union players.

The efficacy of acute nutritional interventions on soccer skill performance

BACKGROUND

The use of nutritional ergogenic aids in team sports such as soccer is now commonplace. Aligned with the primary aim of soccer, which is to score more goals than the opposition within the allotted time, the quality of performance of technical actions (i.e., skills) executed during soccer-specific exercise is likely to determine success. However, when seeking to maintain soccer skill performance, information about the efficacy of nutritional interventions is lacking and factors which might modulate the efficacy of such strategies are unclear.

OBJECTIVE

This review aimed (i) to systematically evaluate the current research that examines the efficacy of nutritional interventions on soccer skills, and (ii) to provide a qualitative commentary on factors that have the potential to modulate the efficacy of such strategies.

DATA SOURCES

Relevant databases (PubMed and SPORTDiscus) were searched up to and including 1 July, 2013 for studies that investigated the efficacy of acute nutritional interventions on soccer skill performances.

STUDY SELECTION

Overall, 279 records were retrieved. Articles were sequentially excluded from the review based on specific criteria, being: (A) articles that did not report outcomes directly relating to skilled performances in soccer, (B) articles that examined the influence of interventions that were not nutritional in origin and/or were nutritional in origin but provided >3 hours before skill testing commenced, (C) articles that were review papers, and (D) post-acceptance withdrawal of articles methods from database.

STUDY APPRAISAL AND SYNTHESIS METHODS

Articles were independently assessed for the quality of the methods employed based upon the Physiotherapy Evidence Database (PEDro) scale. Records achieving a minimum PEDro score of 5 out of 10 were included in this review. Qualitative appraisal of 13 articles was performed after the application of exclusion criteria and quality assurance processes. The majority (n = 8) of articles examined the influence of carbohydrates on technical performance whereas fewer studies investigated the influence of caffeine ingestion (n = 2) and fluid provision (n = 3).

RESULTS

Findings were reported for a total of 171 participants and all but one of the included articles used cross-over study designs. Most participants (94 %) were male, highly trained (reported maximal aerobic capacity range 50-59 ml·kg(-1)·min(-1)) and exercised in temperate environments (reported temperature range 13-25 °C). Six of the eight studies reported that carbohydrates, consumed in the form of a 6-8 % solution of glucose, sucrose or maltodextrin at rates of 30-60 g·h(-1), enhanced at least one aspect of skilled performance over the duration of exercise (75-90 min). Although some evidence exists to support the consumption of caffeine (6 mg·kg(-1) body mass [BM]) and prescribed fluid to preserve skills performed during soccer-specific exercise, findings from the small number of included studies were inconsistent.

LIMITATIONS

The outcome measures and methods used to quantify skilled performance were not consistent across studies; consequently, it was not possible to perform meta-analyses to produce pooled effect sizes in this review.

CONCLUSIONS

The findings from this systematic review suggest that nutritional interventions, which provide carbohydrate, caffeine and fluid, have potential to preserve skills performed under conditions that induce soccer-specific fatigue. The weight of current evidence supports the consumption of carbohydrate, but is less conclusive with respect to caffeine and fluid provision. It is likely that the efficacy of a nutritional intervention will be modulated by factors including the dose consumed, the mode of administration, individual responsiveness to the intervention and interactions with other physiological changes occurring during soccer-specific exercise. Consequently, these factors should be considered when using carbohydrates, caffeine and fluid provision to maintain skilled performances in soccer. Future research should seek to optimise the nutritional strategies employed to maintain technical performance throughout match-play.

Tests examining skill outcomes in sport: a systematic review of measurement properties and feasibility

BACKGROUND

A high level of participant skill is influential in determining the outcome of many sports. Thus, tests assessing skill outcomes in sport are commonly used by coaches and researchers to estimate an athlete's ability level, to evaluate the effectiveness of interventions or for the purpose of talent identification.

OBJECTIVE

The objective of this systematic review was to examine the methodological quality, measurement properties and feasibility characteristics of sporting skill outcome tests reported in the peer-reviewed literature.

DATA SOURCES

A search of both SPORTDiscus and MEDLINE databases was undertaken.

STUDY SELECTION

Studies that examined tests of sporting skill outcomes were reviewed. Only studies that investigated measurement properties of the test (reliability or validity) were included. A total of 22 studies met the inclusion/exclusion criteria.

STUDY APPRAISAL AND SYNTHESIS METHODS

A customised checklist of assessment criteria, based on previous research, was utilised for the purpose of this review.

RESULTS

A range of sports were the subject of the 22 studies included in this review, with considerations relating to methodological quality being generally well addressed by authors. A range of methods and statistical procedures were used by researchers to determine the measurement properties of their skill outcome tests. The majority (95%) of the reviewed studies investigated test-retest reliability, and where relevant, inter and intra-rater reliability was also determined. Content validity was examined in 68% of the studies, with most tests investigating multiple skill domains relevant to the sport. Only 18% of studies assessed all three reviewed forms of validity (content, construct and criterion), with just 14% investigating the predictive validity of the test. Test responsiveness was reported in only 9% of studies, whilst feasibility received varying levels of attention.

LIMITATIONS

In organised sport, further tests may exist which have not been investigated in this review. This could be due to such tests firstly not being published in the peer-review literature and secondly, not having their measurement properties (i.e., reliability or validity) examined formally.

CONCLUSIONS

Of the 22 studies included in this review, items relating to test methodological quality were, on the whole, well addressed. Test-retest reliability was determined in all but one of the reviewed studies, whilst most studies investigated at least two aspects of validity (i.e., content, construct or criterion-related validity). Few studies examined predictive validity or responsiveness. While feasibility was addressed in over half of the studies, practicality and test limitations were rarely addressed. Consideration of study quality, measurement properties and feasibility components assessed in this review can assist future researchers when developing or modifying tests of sporting skill outcomes.

Technical performance reduces during the extra-time period of professional soccer match-play

Despite the importance of extra-time in determining progression in specific soccer tournament matches, few studies have profiled the demands of 120-minutes of soccer match-play. With a specific focus on the extra-time period, and using a within-match approach, we examined the influence of prolonged durations of professional soccer match-play on markers of technical (i.e., skilled) performance. In 18 matches involving professional European teams played between 2010 and 2014, this retrospective study quantified the technical actions observed during eight 15-minute epochs (E1: 00∶00-14∶59 min, E2: 15∶00-29∶59 min, E3: 30∶00-44∶59 min, E4: 45∶00-59∶59 min, E5: 60∶00-74∶59 min, E6: 75∶00-89∶59 min, E7: 90∶00-104∶59 min, E8: 105∶00-119∶59 min). Analysis of players who completed the demands of the full 120 min of match-play revealed that the cumulative number of successful passes observed during E8 (61±23) was lower than E1-4 (E1: 88±23, P = 0.001; E2: 77±21, P = 0.005; E3: 79±18, P = 0.001; E4: 80±21, P = 0.001) and E7 (73±20, P = 0.002). Similarly, the total number of passes made in E8 (71±25) was reduced when compared to E1 (102±22, P = 0.001), E3 (91±19, P = 0.002), E4 (93±22, P≤0.0005) and E7 (84±20, P = 0.001). The cumulative number of successful dribbles reduced in E8 (9±4) when compared to E1 (14±4, P = 0.001) and E3 (12±4, P≤0.0005) and the total time the ball was in play was less in E8 (504±61 s) compared to E1 (598±70 s, P≤0.0005). These results demonstrate that match-specific factors reduced particular indices of technical performance in the second half of extra-time. Interventions that seek to maintain skilled performance throughout extra-time warrant further investigation.

Carbohydrate ingestion before and during soccer match play and blood glucose and lactate concentrations

CONTEXT

The ingestion of carbohydrate (CHO) before and during exercise and at halftime is commonly recommended to soccer players for maintaining blood glucose concentrations throughout match play. However, an exercise-induced rebound glycemic response has been observed in the early stages of the second half of simulated soccer-specific exercise when CHO-electrolyte beverages were consumed regularly. Therefore, the metabolic effects of CHO beverage consumption throughout soccer match play remain unclear.

OBJECTIVE

To investigate the blood glucose and blood lactate responses to CHOs ingested before and during soccer match play.

DESIGN

Crossover study.

SETTING

Applied research study.

PATIENTS OR OTHER PARTICIPANTS

Ten male outfield academy soccer players (age = 15.6 ± 0.2 years, height = 1.74 ± 0.02 m, mass = 65.3 ± 1.9 kg, estimated maximal oxygen consumption = 58.4 ± 0.8 mL·kg(-1)·min(-1)).

INTERVENTION(S)

Players received a 6% CHO-electrolyte solution or an electrolyte (placebo) solution 2 hours before kickoff, before each half (within 10 minutes), and every 15 minutes throughout exercise. Blood samples were obtained at rest, every 15 minutes during the match (first half: 0-15, 15-30, and 30-45 minutes; second half: 45-60, 60-75, and 75-90 minutes) and 10 minutes into the halftime break.

MAIN OUTCOME MEASURE(S)

Metabolic responses (blood glucose and blood lactate concentrations) and markers of exercise intensity (heart rate) were recorded.

RESULTS

Supplementation influenced the blood glucose response to exercise (time × treatment interaction effect: P ≤ .05), such that glucose concentrations were higher at 30 to 45 minutes in the CHO than in the placebo condition. However, in the second half, blood glucose concentrations were similar between conditions because of transient reductions from peak values occurring in both trials at halftime. Blood lactate concentrations were elevated above those at rest in the first 15 minutes of exercise (time-of-sample effect: P < .001) and remained elevated throughout exercise. Supplementation did not influence the pattern of response (time × treatment interaction effect: P = .49).

CONCLUSIONS

Ingestion of a 6% CHO-electrolyte beverage before and during soccer match play did not benefit blood glucose concentrations throughout the second half of exercise.

Technical demands of soccer match play in the English championship

The aim of this study was to investigate the effect of match play on the performance of technical actions in professional soccer players. Using computerized notational analysis, technical performance was quantified for the outfield players of one team during the 2010/2011 English Championship season. This retrospective study evaluated temporal patterns in the performance of players who completed more than 10 games (n = 10). Total possessions and number of ball distributions were lower in the second versus the first half of match play (10 ± 7%, p = 0.010 and 11 ± 8% p = 0.009, respectively). Analysis across 15-minute intervals revealed reductions during the last 15-minutes of match play in the total number of possessions (0:00-14:59 minutes: 11.8 ± 1.9 vs. 75:00-89:59 minutes: 9.5 ± 1.7, p < 0.05) and distributions (0:00-14:59 minutes: 10.9 ± 2.3 vs. 75:00-89:59 minutes: 8.7 ± 2.1, p < 0.05). The number of touches taken per possession, number of challenges, percentage of challenges won, length of forward distributions and percentage success of distributions were all similar between halves and across 15-minute intervals. These results demonstrate that match-specific factors reduced total possessions and number of passes in the second half of match play. Coaching staff could use this information to inform team tactics and technical training sessions.

Physical and physiological demands of elite team handball

This study aimed to analyze elite team handball physical and physiological demands during match play. Time-motion (N = 30) and heart rate (HR; N = 60) analyses were performed throughout 10 official matches. The defined locomotor categories were standing still, walking, jogging, fast running, sprinting, backwards movement, sideways medium-intensity movement, and sideways high-intensity movement, and playing actions studied were jumps, shots, stops when preceded by high-intensity activities, changes of direction and one-on-one situations. During matches, the mean distances covered were 4,370 ± 702.0 m. Around 80% of the total time was spent standing still (43.0 ± 9.27%) and walking (35.0 ± 6.94%) and only 0.4 ± 0.31% with sprinting. The most frequent high-intensity actions were stops, changes of direction, and one-on-one situations. Effective mean HR was 157 ± 18.0 b·min(-1) (82 ± 9.3% of HRmax), and total HR was 139 ± 31.9 b·min(-1) (72 ± 16.7% of HRmax). The HR, time spent in high-intensity activities, frequency of stops, changes of direction, one-on-one situations, and most intense periods of the game were higher during the first half than during the second half (p ≤ 0.05). The opposite was observed for the number of time outs and the time between each change of activity (p = 0.00). Handball is an intermittent exercise that primarily uses aerobic metabolism, interspersed by high-intensity actions that greatly tax anaerobic metabolism. Additionally, exercise intensity decreases from the first to the second half of the match, suggesting that neuromuscular fatigue may occur during the game. The training of elite handball players should comprise exercises targeting the ability to perform specific high-intensity actions throughout the game and to rapidly recover during the less intense periods.

Effects of carbohydrate-hydration strategies on glucose metabolism, sprint performance and hydration during a soccer match simulation in recreational players

OBJECTIVES

This study compared the effects of three carbohydrate-hydration strategies on blood glucose concentration, exercise performance and hydration status throughout simulated soccer match-play.

DESIGN

A randomized, double-blind and cross-over study design was employed.

METHODS

After familiarization, 14 recreational soccer players completed the soccer match simulation on three separate occasions. Participants consumed equal volumes of 9.6% carbohydrate-caffeine-electrolyte (∼ 6 mg/kg BW caffeine) solution with carbohydrate-electrolyte gels (H-CHO), 5.6% carbohydrate-electrolyte solution with electrolyte gels (CHO) or electrolyte solution and electrolyte gels (PL). Blood samples were taken at rest, immediately before exercise and every 15 min during exercise (first half: 15, 30, 45 min; second half: 60, 75, 90 min).

RESULTS

Supplementation influenced blood glucose concentration (time × treatment interaction: p<0.001); however, none of the supplementation regimes were effective in preventing a drop in blood glucose at 60 min. Mean sprint speed was 3 ± 1% faster in H-CHO when compared with PL (treatment: p=0.047). Supplementation caused a 2.3 ± 0.5% increase in plasma osmolality in H-CHO (p<0.001) without change in CHO or PL. Similarly, mean sodium concentrations were 2.1 ± 0.4% higher in H-CHO when compared with PL (p=0.006).

CONCLUSIONS

Combining high carbohydrate availability with caffeine resulted in improved sprint performance and elevated blood glucose concentrations throughout the first half and at 90 min of exercise; however, this supplementation strategy negatively influenced hydration status when compared with 5.6% carbohydrate-electrolyte and electrolyte solutions.