Influence of football match time–motion parameters on recovery time course of muscle damage and jump ability

Post-Match Recovery Responses in Italian Serie A Youth Soccer Players: Effects of Manipulating Training Load 48 h After Match Play

This study described the recovery responses following match play and examined the effects of manipulating training load 48 h post-match in Italian Serie A youth soccer players. Forty-eight players were assessed using the countermovement jump (CMJ), isometric posterior-chain muscle test (IPC), muscle soreness and fatigue before (pre) and after (0.5 h post, 48 h post and 72 h post) a match. At 48 h post-match, players were randomly assigned to a complete training (CT; n = 26) or a reduced training (RT; n = 22) group. Recovery differences were analysed between time points and training groups, with training loads quantified on match day (MD) and match day plus two (MD + 2). Recovery measures were impaired immediately post-match (p < 0.05). IPC and muscle soreness demonstrated incomplete recovery 48 h post-match (p < 0.05), whereas CMJ and fatigue returned to baseline (p > 0.05). Training load on MD did not differ between groups (p > 0.05), whereas the CT group had higher load on MD + 2 compared to RT (p < 0.05). A significant time × group interaction was observed for CMJ height and IPC measures (p < 0.05), with reductions in physical performance observed in the CT group from 48 to 72 h post-match (p < 0.05). A youth soccer match acutely impaired physical performance and recovery status, with prolonged and incomplete recovery of hamstring force and elevated muscle soreness 48 h post-match. A high-volume and high-intensity session administered 48 h post-match negatively influenced physical performance compared to a moderate training session.

Comparison of six-week flywheel and traditional resistance training on deceleration and dynamic balance in elite badminton players

Introduction

The aim of this study was to compare the effects of flywheel resistance training (FRT) and traditional resistance training (TRT) on deceleration and dynamic balance performance in elite badminton players.

Methods

Seventeen elite male badminton players (age: 21.36 ± 2.10 years) volunteered to participate and were randomly assigned to either a flywheel resistance training group (FT: n = 8) or a traditional resistance training group (RT: n = 9). The FT group performed flywheel resistance training twice a week for 6 weeks, while the RT group participated in traditional resistance training for the same period. Deceleration and dynamic balance performance were assessed at baseline and following the intervention using the dynamic posture stability index (DPSI) test, 5-0-5 change of direction (COD) test, deceleration deficit (DD) test, and isometric mid-thigh pull (IMTP) test.

Results and Discussion

Repeated-measures ANOVA revealed a significant time × group interaction for DPSI of both legs and peak force in the IMTP test (p < 0.05, partial η 2 = 0.42-0.79), with better post-test performance compared to pre-test result in the FT group (ES = 0.30-2.10), and the improvements were higher than that of the RT group. No significant differences were observed in the DD test and COD test between FT and RT groups (p > 0.05); however, the magnitude of improvement in DD for the FT group (ES = 0.99) was greater than that of the RT group (ES = 0.52). This pilot study demonstrates that, compared to traditional resistance training, flywheel resistance training enhances deceleration performance and improves dynamic balance in elite badminton players.

Automated Detection of Change of Direction in Basketball Players Using Xsens Motion Tracking

In sports science, accurate tracking of athletes' movement patterns is essential for performance analysis and injury prevention. Changes of direction (COD), frequently executed during basketball games at cutting angles of around 135° (internal angle of 45°), are essential for agility and high-level performance. Moreover, mastering effective COD mechanics is associated with a lower risk of injuries and enhanced long-term athletic success. However, manual segmentation of data from wearable sensors is labor-intensive and time-consuming, often creating bottlenecks for sports practitioners. The aim of this study was to evaluate the feasibility and accuracy of an automated algorithm for detecting COD movements in basketball and to compare its performance with manual detection methods. Data were collected from 62 basketball players, each completing two tests (V-cut test and a modified V-cut test), totaling 248 trials. The system utilizes kinematic data from an Xsens full-body kit to analyze key variables that characterize direction changes. The proposed method detects COD events with a median error of one frame and an interquartile range of two frames. The system demonstrated nearly 80% accuracy in COD detection, as validated against manual video analysis. These findings indicate that automated COD detection can significantly reduce segmentation time for practitioners while providing actionable, data-driven insights to enhance kinematic assessment during sport-specific activities.

The Relationship Between Individually Assessed High-Intensity Accelerations, High-Intensity Decelerations, Sprints, and Technical Performances During Soccer Matches: A Full Season Analysis

Purpose: This longitudinal study analyzed the relationship between players' physical (sprint distances, number of high-intensity accelerations and decelerations assessed with individual and relative thresholds) and technical (retrieved from SofaScore platform) performances during competition. Methods: Twenty elite players were monitored across a full season. Physical performances were monitored with GNSS devices, retrieving time (s), velocity (km.h-1) and distance (m). Sprint distances were calculated as > 80% of the match peak speed registered across the season. High-intensity accelerations and decelerations were calculated as >75% of the peak values registered across the season. Pearson (r) correlations (with 95% confidence intervals) were calculated to assess the relationship among different physical performance variables and between the physical and technical performance variables. Results: Sprint distances correlated with the number of ball touches (r = -0.36 [-0.49, -0.23], p < .001), accurate passes (r = -0.45 [-0.56, -0.32], p < .001), and dribble attempts (r = 0.30 [0.16, 0.43], p < .001). If players touched the ball more frequently and pass the ball more accurately, they covered shorter sprint distances. However, if players attempted more dribbles, they covered longer sprint distances. Conclusion: Practitioners can develop tactical strategies considering the relationship between sprint distances and technical variables such as ball touches, accurate passes, and dribble attempts.

Forces experienced at different levels of the musculoskeletal system during horizontal decelerations

Horizontal decelerations are frequently performed during team sports and are closely linked to sports performance and injury. This study aims to provide a comprehensive description of the kinetic demands of decelerations at the whole-body, structural, and tissue-specific levels of the musculoskeletal system. Team-sports athletes performed maximal-effort horizontal decelerations whilst full-body kinematics and ground reaction forces (GRFs) were recorded. A musculoskeletal model was used to determine whole-body (GRFs), structural (ankle, knee, and hip joint moments and contact forces), and tissue (twelve lower-limb muscle forces) loads. External GRFs in this study, especially in the horizontal direction, were up to six times those experienced during accelerated or constant-speed running reported in the literature. To cope with these high external forces, large joint moments (hip immediately after touchdown; ankle and knee during mid and late stance) and contact forces (ankle, knee, hip immediately after touchdown) were observed. Furthermore, eccentric force requirements of the tibialis anterior, soleus, quadriceps, and gluteal muscles were particularly high. The presented loading patterns provide the first empirical explanations for why decelerating movements are amongst the most challenging in team sports and can help inform deceleration-specific training prescription to target horizontal deceleration performance, or fatigue and injury resistance in team-sports athletes.

The association between physical outputs and match outcome across different playing styles for a professional second-tier football team across two complete seasons

BACKGROUND

Elite-level football requires an array of physical, technical, psychological, and tactical skills. The aim of this study was to measure the association between physical outputs (distance, decelerations, accelerations) and the match outcome (win, draw, lose) in professional football. This research also examined whether the same association is influenced if a team adopts a possession or transition-based playing style.

METHODS

Thirty-six elite-outfield football players from an English Championship team participated in the study during the 2020/2021 and 2021/2022 seasons using physical and event data collected from an English Championship club over the 2020-2021 and 2021-2022 seasons, this study conducted a univariate analysis of variance (ANOVA) and Hedge g effect size (ES) to measure the research aims.

RESULTS

The results showed no significant differences were found between match outcomes for each physical output metric calculated. There was a trivial ES shown for all conditions except decelerations, with win/lose having a moderate ES (g=0.53). When playing a possession-based playing style there was no significant difference or non-trivial ES found for any physical output and match outcomes. When playing a transition-based playing style there was a moderate ES found for win/draw (P=0.38, g=0.90) and win/loss (P=0.98, g=0.64).

CONCLUSIONS

This research provides important evidence for utilizing intense deceleration actions as a physical KPI during match play for teams adopting a transitional playing style. Subsequently, training interventions should be adopted to physically prepare players to complete and sustain intense deceleration actions during match play.

Adapting the percentage intensity method to assess accelerations and decelerations in football: moving beyond absolute and arbitrary thresholds

 We adapted the percentage intensity approach to monitor accelerations and decelerations allowing players' individualisation. Forty-two players were monitored during four microcycles via global navigation satellite system devices. Raw velocity and time data were collected to calculate acceleration and deceleration magnitudes according to specific starting speed intervals, and the efforts intensities were established as very low (<25% of the maximal effort), low (25-50%), moderate (50-75%) and high (>75%). Linear regressions and Pearson correlation (r) analysed the relationship between maximal efforts and starting speeds; additionally, mean paired differences compared efforts magnitudes between subsequent starting speed intervals. Most very low intensity accelerations (86%) and decelerations (79%) started from <5 km.h-1. Correlation between maximal efforts and starting speeds were r = -0.97 (p < .001) for acceleration, and r = -0.94 (p < .01) for deceleration. Maximal acceleration decreased as starting speed increases (very large effect sizes), but deceleration is less starting speed dependent (unclear to large effect sizes). This adaptation allows practitioners to individualise accelerations and decelerations classification during real-life scenarios, leading to a more precise training prescription. The very low intensity interval could be excluded to consider only relevant efforts. Maximal acceleration should be collected for each starting speed interval because accelerations are starting speed dependents.

The effect of post-match fatigue on physical performance in adolescent soccer players

BACKGROUND

Soccer involves many physically challenging actions and engaging in such activities can induce a decline in performance due to physical fatigue which predisposes players to develop injuries. The present study aimed to examine the impact of post-match fatigue on functional performance and Inter-Limb Asymmetry Index (LSI) in adolescent soccer players.

METHODS

Thirty-eight adolescent male soccer players (15-18 years) completed a battery of functional performance measures (Rate of Perceived Exertion (RPE) scale, 10 m sprint, agility T-test, and Single leg hop for distance (SLHD) test). The data collection started prior to a soccer match and consisted of two testing sessions; two hours before the match, while the subsequent testing session was performed within two hours immediately following the match.

RESULTS

The study results revealed a significant effect of post-match fatigue on change of direction abilities and SLHD (moderate effect size). However, no significant differences were observed in the 10 m sprint test and LSI (P>0.05).

CONCLUSIONS

Functional performance measures such as agility test and SLHD test can detect physical ability changes due to post-match fatigue in adolescent soccer players. The study findings offer insightful and practical information on the importance of employing field-based functional performance measures in monitoring players' recovery following a game.

Football Movement Profile-Based Creatine-Kinase Prediction Performs Similarly to Global Positioning System-Derived Machine Learning Models in National-Team Soccer Players

PURPOSE

The relationship between external load and creatine-kinase (CK) response at the team/position or individual level using Global Positioning Systems (GPS) has been studied. This study aimed to compare GPS-derived and Football Movement Profile (FMP) -derived CK-prediction models for national-team soccer players. The second aim was to compare the performance of general and individualized CK prediction models.

METHODS

Four hundred forty-four national-team soccer players (under 15 [U15] to senior) were monitored during training sessions and matches using GPS. CK was measured every morning from whole blood. The players had 19.3 (18.1) individual GPS-CK pairs, resulting in a total of 8570 data points. Machine learning models were built using (1) GPS-derived or (2) FMP-based parameters or (3) the combination of the 2 to predict the following days' CK value. The performance of general and individual-specific prediction models was compared. The performance of the models was described by R2 and the root-mean-square error (RMSE, in units per liter for CK values).

RESULTS

The FMP model (R2 = .60, RMSE = 144.6 U/L) performed similarly to the GPS-based model (R2 = .62, RMSE = 141.2 U/L) and the combination of the 2 (R2 = .62, RMSE = 140.3 U/L). The prediction power of the general model was better on average (R2 = .57 vs R2 = .37) and for 73% of the players than the individualized model.

CONCLUSIONS

The results suggest that FMP-based CK-prediction models perform similarly to those based on GPS-derived metrics. General machine learning models' prediction power was higher than those of the individual-specific models. These findings can be used to monitor postmatch recovery strategies and to optimize weekly training periodization.

The effect of electro-magnetic-energy-regulation therapy on subjective sleep among elite players in Norwegian women's football

The current study investigated if Bio-Electro-Magnetic-Energy-Regulation (BEMER) therapy is affecting subjective sleep among a sample of 21 elite female football players in a Norwegian top series club. Subjective sleep was measured each day over a period of 273 consecutive days by using a smartphone application, PM Reporter Pro, which scheduled push messages to remind the participants to report sleep every morning. The study was conducted as a quasi-experimental design, with a control period before the introduction of BEMER therapy that lasted for 3 months, followed by an intervention period where BEMER therapy was used that lasted for 5 months. The collected data from the players in the control period served as their control compared to the data collected from the players in the intervention period. Analyses of variance (ANOVA) with False Discovery Rate adjusted p-values show that subjective sleep duration and subjective sleep quality are significantly reduced on game nights, both in the control period and in the experiment period. The results also show that subjective sleep duration and subjective sleep quality significantly increase in the experiment period compared to the control period. The findings indicate that BEMER therapy might serve as a tool to improve sleep.

Using Bar Velocity to Assess Post-match Neuromuscular Fatigue in Young Soccer Players

This study aimed to investigate the recovery of neuromuscular performance using mechanical parameters collected during jump (vertical and horizontal) and strength-power exercises in youth soccer players after official soccer matches. Twenty-one outfield highly trained youth male soccer athletes (age: 18.23±0.73 years; weight: 72.12±6.99 kg; height: 1.78±0.08 m) from two teams competing in the 1st division of U-19 Portuguese National Championship participated in this study. Players completed a battery of physical tests at -2 h, + 30 min, +24 h, and +48 h in relation to the match. Countermovement jump height, horizontal jump distance, and bar velocity during the half squat, bench press, and hip thrust exercises, at fixed loads, were recorded. Countermovement jump was impaired until 24 h post-match (-: 1.7% from pre- to 24 h post-match, p=0.050; ES=-: 0.82). Half-squat bar velocity was reduced immediately following the match (-: 6.8% from pre-match, p=0.004; ES=-: 0.64) but recovered at +24 h (+2.9%, p=1.00; ES=0.02). Hip-thrust bar velocity was reduced for up to 48 h post-match (-: 7.4% from pre- to 48 h post-match, p<0.001; ES=-: 0.80). No impairments were found in the horizontal jump and bench press at any moment. Our findings show prolonged decrements in strength of the posterior chain following a soccer match, measured in the hip thrust exercise, while the other exercises displayed faster recovery dynamics.

Effects of variable intensity and constant intensity flywheel resistance training programs on specific soccer players' performance

Resistance training programs play a crucial role in optimizing soccer performance. The aim of this study is to compare performance outcomes in sport-specific tasks after implementing two different flywheel resistance training (FRT) programs: variable intensity (VI) and constant intensity (CI). Seventeen (n = 17) amateur footballers were divided into VI and CI groups with the same training volume. For the VI group, a decrease in inertial load was implemented every four sessions, whereas the CI group maintained a constant load during the entire program. After different familiarization sessions and testing (sprint, change of direction, jump, one-repetition maximum and flywheel strength variables), ten sessions of FRT were performed over 5 weeks. Both groups showed similar improvements in the one-repetition maximum (p < 0.01) but the CI group had significant improvements in the 10-m sprint (p = 0.04; ES = 0.72), emphasizing the potential benefits of medium inertial loads to maximize power and specificity in sport tasks. However, no significant differences were observed in the countermovement jump, change of direction and 30-m sprint, possibly attributed to neuromuscular fatigue from a high-volume training schedule and friendly matches. The study highlights the importance of considering training load distribution in FRT programs. The findings emphasize the need for complementary training to maximize the jump and change of direction abilities and caution against high-volume training and friendly match scenarios. In conclusion, FRT programs, whether varying in intensity or not, can yield medium-term performance improvements for soccer players.

Monitoring load, wellness, and psychological variables in female and male youth national team football players during international and domestic playing periods

Aim

To study differences in total load exposure, wellness, and psychological variables in youth female (N = 19) and male (N = 20) national team football players during domestic and international playing periods, respectively.

Procedures

The players filled out questionnaires on well-being, stress, and resilience before and after both playing periods lasting 8 days each. The Hooper index was used to monitor daily wellness levels during both playing periods. The number of training sessions and matches were recorded, and the session rating of perceived exertion was collected. Training load, monotony, and strain were calculated. Daily measurements were used to evaluate in-period changes, and composite scores were used to describe differences between periods.

Results

The international compared to the domestic playing period was for both groups characterized by more matches played, longer field training session durations, and of fewer gym-based sessions (P < 0.05). The male players increased total exposure time (25%; P < 0.05), monotony (P < 0.001), and strain (P < 0.001), which was not changed in the female players. Well-being decreased (P < 0.05) during the international playing period in male players. Stress levels were higher (P < 0.05) for both genders during the international compared to the domestic playing period. During the international playing period, positive correlations were found between the initial levels of stress, and the change in stress (P = 0.03; r2 = 0.12), and between the changes in total load and changes in well-being (P = 0.02; r2 = 0.12), whereas a negative correlation was found between the changes in wellness and stress (P = 0.03; r2 = 0.14).

Conclusion

A playing period characterized by increased match focus, longer field training sessions, and fewer gym-based training activities may lead to changes in the physical and mental profiles of youth national team football players. Alterations to load exposure and wellness may influence mental health. Players with high initial stress levels may be subjected to greater changes compared to other players. Sports scientists and medical staff may benefit from initiating structured monitoring systems to track alterations in physical load and mental health in youth national team players.

Training Volume and High-Speed Loads Vary Within Microcycle in Elite North American Soccer Players

ABSTRACT

Ishida, A, Draper, G, Wright, M, Emerson, J, and Stone, MH. Training volume and high-speed loads vary within microcycle in elite North American soccer players. J Strength Cond Res 37(11): 2229-2234, 2023-The purposes of this study were to reduce dimensionality of external training load variables and examine how the selected variables varied within microcycle in elite North American soccer players. Data were collected from 18 players during 2018-2020 in-seasons. Microcycle was categorized as 1, 2, 3, 4, 5 days before match day (MD-1, MD-2, MD-3, MD-4, and MD-5, respectively). Training load variables included total distance, average speed, maximum velocity, high-speed running distance (HSR), average HSR, HSR efforts, average HSR efforts, sprint distance, average sprint distance, sprint efforts, average sprint efforts, total PlayerLoad, and average PlayerLoad. The first principal component (PC) can explain 66.0% of the variances and be represented by "high-speed load" (e.g., HSR and sprint-related variables) with the second PC relating to "volume" (e.g., total distance and PlayerLoad) accounting for 17.9% of the variance. Average sprint distance and total distance were selected for further analysis. Average sprint distance was significantly higher at MD-3 than at MD-2 (p = 0.01, mean difference = 0.36 m•minute-1, 95% confidence intervals [CIs] = 0.07-0.65 m•minute-1) and MD-4 (p = 0.012, mean difference = 0.26 m•minute-1, 95% CIs = 0.10-0.41 m•minute-1). Total distance was significantly higher at MD-3 than at MD-1 (p < 0.001, mean difference = 1,465 m, 95% CIs = 1,003-1926 m), and MD-2 (p < 0.001, mean difference = 941 m, 95% CIs = 523-1,360 m). Principal component analysis may simplify reporting process of external training loads. Practitioners may need to choose "volume" and "high-speed load" variables. Elite North American Soccer players may accumulate higher average sprint distance at MD-3 than at other training days.

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.

Individual-Specific Relationship Between External Training and Match Load and Creatine-Kinase Response in Youth National Team Soccer Players

BACKGROUND

Previous studies have examined the relationship between external load and creatine-kinase (CK) response at the team level. This study aimed to build individualized CK prediction models for elite youth national team soccer players.

HYPOTHESIS

The CK response of youth soccer players can be categorized as being sensitive to micromovements (MM), high-velocity (HV) parameters, or the combination of both, measured during training sessions and matches.

STUDY DESIGN

Prospective cohort study.

LEVEL OF EVIDENCE

Level 4.

METHODS

A total of 25 U16-U17 youth national team soccer players were monitored during training sessions and matches using global positioning system (GPS) units. Individual CK values were measured every morning from whole blood. The data set consisted of 57 ± 17 individual datapoints per player. Individual prediction models were used to examine the relationship between external load and consecutive CK changes. Numerous models were built for each player using MM, HV parameters, or the combination of both. The performance of the models was described by the R2 and the root mean square error (RMSE, U/l for CK values).

RESULTS

The MM models were superior for 8 players (R2 = 0.68; RMSE = 113 U/l), followed by HV (8 players; R2 = 0.69; RMSE = 88 U/l) and the combined models (2 players; R2 = 0.64; RMSE = 141 U/l). For the remaining 7 players, the R2 of the models was <0.5. The recovery time between efforts was more important in the HV model.

CONCLUSION

Players could be categorized on sensitivity to MM, HV movements, or the combination of both.

CLINICAL RELEVANCE

These findings can be used to individualize postmatch recovery strategies and to optimize weekly training periodization to maximize match performance.

Association between physical demands, skin temperature and wellbeing status in elite football players

The demanding nature of elite football requires players to be closely monitored to ensure optimal performance and minimize injury risk. This study aimed to evaluate the relationship between physical demands, skin temperature, and well-being status in 30 elite football players over a 12-week competitive period. Thermography assessments, weekly Well-being questionnaires, and daily training and match load recordings were used to gather data. Results indicated that along the microcycles there was a decrease in high-intensity accelerations and decelerations distance completed, while maintaining other high-intensity actions. Furthermore, it was found that high-intensity movements contribute to the generation of thermal asymmetries in the thighs; the adductor thermal asymmetry showed a positive relationship with stress and muscle soreness, the knee thermal asymmetry had a positive relationship with fatigue and a negative relationship with rest and quality of rest, and finally the hamstrings muscles exhibited significant differences between the thermal asymmetry groups, with the high asymmetry completing less high intensity actions than the low asymmetry group. In conclusion, this study highlights the interconnections between physical demands, skin temperature, and well-being in elite football players and provides valuable insights for coaches and trainers in their efforts to optimize performance and health.

The effect of bio-electro-magnetic-energy-regulation therapy on sleep duration and sleep quality among elite players in Norwegian women's football

The current study investigated if physical loads peak on game days and if Bio-Electro-Magnetic-Energy-Regulation (BEMER) therapy is affecting sleep duration and sleep quality on nights related to game nights among elite players in Norwegian women's elite football. The sample included 21 female football players from an elite top series club with a mean age of ~24 years (± 2.8). Sleep was measured every day over a period of 273 consecutive days with a Somnofy sleep monitor based on ultra-wideband (IR-UWB) pulse radar and Doppler technology. The current study was conducted as a quasi-experiment, where each player was their own control based on a control period that lasted for 3 months, and an experimental period that lasted for 5 months. Accordantly, the time each player spent with BEMER therapy was used as a control variable. Multivariate analyses of variance using FFMANOVA and univariate ANOVA with False Discovery Rate adjusted p-values show that physical performance (total distance, distance per minute, sprint meters >22.5 kmh, accelerations and decelerations) significantly peak on game day compared with ordinary training days and days related to game days. The results also show that sleep quantity and quality are significantly reduced on game night, which indicate disturbed sleep caused by the peak in physical load. Most sleep variables significantly increased in the experiment period, where BEMER therapy was used, compared to the control period before the introduction of BEMER therapy. Further, the analyses show that players who spent BEMER therapy >440 h had the most positive effects on their sleep, and that these effects were significantly compared to the players who used BEMER therapy <440 h. The findings are discussed based on the function of sleep and the different sleep stages have on recovery.

Reliability and sensitivity to change of post-match physical performance measures in elite youth soccer players

Introduction

To effectively monitor post-match changes in physical performance, valid, reliable and practical measures which are sensitive to change are required. This study aimed to quantify test-retest reliability and sensitivity to change of a range of physical performance measures recorded during an isometric posterior chain (IPC) lower-limb muscle test and a countermovement jump (CMJ) test.

Methods

Eighteen Italian Serie A academy soccer players performed three IPC repetitions per limb and five CMJ trials in 4 testing sessions. Test-retest reliability was evaluated between two testing sessions seven days apart using typical error of measurement, coefficient of variation and intraclass correlation coefficient. Sensitivity to change was assessed on two additional testing sessions performed before and immediately after a soccer match through Hedges' g effect size (g) and comparisons to typical error.

Results

Absolute reliability (coefficient of variations) ranged from 1.5 to 8.8%. IPC and CMJ measures demonstrated moderate to excellent relative reliability (intraclass correlation coefficients ranged from 0.70 to 0.98). A wide range of physical performance measures showed significant alterations post-match (p < 0.05; g: small to moderate). IPC peak force and torque, CMJ reactive strength index modified, CMJ eccentric forces (mean breaking force, mean deceleration force, peak force, force at zero velocity) and CMJ mean power measures had post-match changes greater than their typical variation, demonstrating acceptable sensitivity in detecting performance changes at post-match.

Discussion

IPC peak force and torque, CMJ reactive strength index modified, CMJ eccentric phase forces and CMJ mean power were found to be both reliable and sensitive to change, and thus may be appropriate for monitoring post-match neuromuscular performance in youth soccer population.

Relationship Between Body Size and Skeletal Age with Muscle Damage in Young Soccer Players

This study verified the relationship between body size and skeletal age (SA) with the behavior of blood markers of muscle damage and delayed onset muscle soreness (DOMS) after a soccer match in the U-13 and U-15 categories. The sample consisted of 28 soccer players in the U-13 and 16 in the U-15 categories. Creatine kinase (CK), lactate dehydrogenase (LDH), and DOMS were evaluated up to 72 h after the match. Muscle damage was elevated at 0 h in U-13, and from 0 h to 24 h in U-15. DOMS increased from 0 h to 72 h in U-13 and from 0 h to 48 h in U-15. Significant associations of SA and fat-free mass (FFM) with muscle damage markers and DOMS were observed only in U-13, specifically at time 0 h, when SA explained 56% of CK and 48% of DOMS and FFM explained 48% of DOMS. We concluded that in the U-13 category, higher SA is significantly associated with muscle damage markers, and increase in FFM is associated with muscle damage markers and DOMS. Furthermore, U-13 players need 24 h to recover pre-match muscle damage markers and more than 72 h to recover DOMS. In contrast, the U-15 category needs 48 h to recover muscle damage markers and 72 h to recover DOMS.

Assessment of a New Change of Direction Detection Algorithm Based on Inertial Data

The purpose of this study was to study the validity and reproducibility of an algorithm capable of combining information from Inertial and Magnetic Measurement Units (IMMUs) to detect changes of direction (COD). Five participants wore three devices at the same time to perform five CODs in three different conditions: angle (45°, 90°, 135° and 180°), direction (left and right), and running speed (13 and 18 km/h). For the testing, the combination of different % of smoothing applied to the signal (20%, 30% and 40%) and minimum intensity peak (PmI) for each event (0.8 G, 0.9 G, and 1.0 G) was applied. The values recorded with the sensors were contrasted with observation and coding from video. At 13 km/h, the combination of 30% smoothing and 0.9 G PmI was the one that showed the most accurate values (IMMU1: Cohen's d (d) = -0.29;%Diff = -4%; IMMU2: d = 0.04 %Diff = 0%, IMMU3: d = -0.27, %Diff = 13%). At 18 km/h, the 40% and 0.9 G combination was the most accurate (IMMU1: d = -0.28; %Diff = -4%; IMMU2 = d = -0.16; %Diff = -1%; IMMU3 = d = -0.26; %Diff = -2%). The results suggest the need to apply specific filters to the algorithm based on speed, in order to accurately detect COD.

Effect of Acute Judo Training on Countermovement Jump Performance and Perceived Fatigue among Collegiate Athletes

This study focused on the effect of acute Judo training on countermovement jump (CMJ) performance and perceived fatigue among a group of highly trained collegiate judo athletes. Twenty male judo athletes participated in this study (age: 20.65 ± 1.22 years, weight: 84.17 ± 28.45 kg). Participants were assessed for CMJperformance changes before, immediately after (0 h), 12 h after, and 24 h after judo training (JT) using unloaded CMJ(CMJ_unloaded) and loaded CMJ(CMJ_loaded). All the jumps were performed on a force plate, and the force-time curves were collected for further analysis. Respondents' perceptions were evaluated using the modified rating of perceived exertion (mRPE) before, after (0 h), 12 h, and 24 h after JT. CMJparameters were analyzed at four measured points using a one-way repeated analysis of variance. Effect sizes (ES) and percentage changes before versus 24 h after JT were calculated for comparison. Associations between the CMJparameters and mRPE were analyzed using the Pearson product-moment correlation. The ratio of flight time to contact time significantly decreased, whereas the eccentric duration, concentric duration, and total duration significantly increased (p < 0.05) in both CMJs 24 h after JT. Compared with CMJ_unloaded, CMJ_loaded had a significantly lower (p < 0.05) flight time, jump height, peak velocity, and peak power. The mRPE and CMJ_loaded peak velocity showed moderate- to high-level negative correlation results both 0 and 24 h after training (r = -0.543, p < 0.05; r = -0.479, p < 0.05). In this study, we only observed the effect of fatigue on the neuromuscular (NM) system 24 h after JT. CMJ_loaded height may help to better determine fatigue state compared with CMJ_unloaded. According to the results, the neuromuscular effects of fatigue were not observed until 24 h after a single high-intensity training. Therefore, when arranging high-intensity special training or strength and conditioning training, one should reduce the volume of training appropriately to avoid fatigue accumulation and reduce the risk of sports injuries.

Match Loads May Predict Neuromuscular Fatigue and Intermittent-Running Endurance Capacity Decrement after a Soccer Match

How the match-derived load metrics relate to post-match fatigue in soccer is scarcely researched. Thus, the aim of this study was to determine the associations between soccer match-related internal and external loads, neuromuscular performance decrease and intermittent-running endurance capacity decrement immediately post-match. Vertical jump (countermovement jump), straight-line sprinting (10- and 20-m sprint), change of direction ability (T-test) and intermittent-running endurance capacity (YO-YO intermittent recovery level 2) were measured one day before and immediately after a friendly match in male soccer players. During the match, players' internal and external loads were also monitored, including heart rate-derived indices, total distance at various speed thresholds, average running velocity, maximal running velocity, number of sprints and number of accelerations and decelerations at various intensity thresholds. The results show that match-induced fatigue was reflected on neuromuscular performance and intermittent-running endurance capacity immediately post-match (p < 0.05). The quantification of percentage change of match external-load metrics, particularly accelerations and decelerations, provides a useful non-invasive predictor of subsequent neuromuscular fatigue status in soccer players immediately post-match (p < 0.05). However, only internal load metrics present a practical application for predicting intermittent-running endurance capacity impairment (p < 0.05). In summary, internal and external load metrics may allow for predicting the extent of acute fatigue, and variability between halves may represent a valuable alternative to facilitate the analysis of match-related fatigue both for research and applied purposes.

Melatonin supplementation alleviates cellular damage and physical performance decline induced by an intensive training period in professional soccer players

Melatonin has been proved to have positive effects on cellular damage and metabolic regulation. The aim of the study was to determine the effect of melatonin supplementation during an intensive training period on physical performance decline, oxidative stress and cellular damage state. The investigation was conducted on 20 soccer players who participated in an exhaustive six-day training schedule associated with daily 5 mg oral melatonin or placebo ingestion. Resting blood samples and physical performance were measured before and after the training period. The mixed 2-way ANOVA (group x training camp) showed that compared to placebo, melatonin intake prevented an increase in advanced oxidation protein products (p>0.05) and increased the antioxidant enzyme activity (i.e., superoxide dismutase; p<0.001). In addition, melatonin prevented an increase of biomarkers of renal function (e.g., creatinine; p>0.05) and biomarkers of muscle (e.g., creatine kinase; p>0.05) and liver (e.g., gamma-glutamyltransferase; p>0.05) damage. Furthermore, melatonin alleviated the deterioration in physical performance (countermovement jump, five-jump test and 20-m sprint; p>0.05). In conclusion, the obtained data showed increased oxidative stress and renal, muscle and liver damage in professional soccer players during an exhaustive training schedule. Melatonin intake during the training period exerts beneficial effects on physical performance and protects tissues against the deleterious effects of reactive oxygen species and cellular damage.

Monitoring the post-match neuromuscular fatigue of young Turkish football players

Neuromuscular fatigue tests have been used in previous studies to organize post-match training programs and to minimize injuries. The aim of this study is to describe the neuromuscular fatigue that occurs after a football match and to examine the relationship between internal and external load values in the match and fatigue parameters obtained at different time intervals. Twenty male U19 academy league soccer players (age: 19; height: 181.3 ± 4.3; weight: 73.4 ± 6.7) participated in the study. The countermovement jump (CMJ) test was applied to the players 24 h before, as well as 24, 48, 72, 96, and 120 h after a football match. During the CMJ tests, the maximum velocity of each player during the jump was recorded by using the GymAware linear position transducer. The CMJ maximum velocity values 24 h before and 24 h after the match, as well as the CMJ height values (Cohen's d: 1.210; p < 0.001), were statistically different from the values recorded 24 h before and 24 and 48 h after the match (Cohen's d: 1.578; p < 0.001; Cohen's d: 0,922; p < 0.009). The correlation values were not statistically significant. The results suggest, CMJ height and CMJ maximum velocity values, which determine neuromuscular fatigue after a football match, can be used by practitioners to display post-match neuromuscular fatigue measurements.

Techniques to derive and clean acceleration and deceleration data of athlete tracking technologies in team sports: A scoping review

The application of acceleration and deceleration data as a measure of an athlete's physical performance is common practice in team sports. Acceleration and deceleration are monitored with athlete tracking technologies during training and games to quantify training load, prevent injury and enhance performance. However, inconsistencies exist throughout the literature in the reported methodological procedures used to quantify acceleration and deceleration. The object of this review was to systematically map and provide a summary of the methodological procedures being used on acceleration and deceleration data obtained from athlete tracking technologies in team sports and describe the applications of the data. Systematic searches of multiple databases were undertaken. To be included, studies must have investigated full body acceleration and/or deceleration data of athlete tracking technologies. The search identified 276 eligible studies. Most studies (60%) did not provide information on how the data was derived and what sequence of steps were taken to clean the data. Acceleration and deceleration data were commonly applied to quantify and describe movement demands using effort metrics. This scoping review identified research gaps in the methodological procedures and deriving and cleaning techniques that warrant future research focussing on their effect on acceleration and deceleration data.

Acceleration and deceleration demands during training sessions in football: a systematic review

PURPOSE

The aim of this review is to summarize the current scientific knowledge about acceleration and deceleration demands during football training.

METHODS

A systematic search of three electronic databases (PubMed, SPORTDiscus, Web of Science) was performed to identify peer-reviewed relevant English-language articles, following PRISMA guidelines.

RESULTS

All acceleration and deceleration data were analyzed and organized into four categories: i) training drills variables (i.e. manipulated drills variables such as number of players in small-sided games), ii) training exercises (i.e. different drills such small games or circuit training), iii) players' positions (i.e. demands for each playing position) and iv) training schedule (i.e. training sessions presented as microcycles, season sections or full season). Full-text articles of 42 studies were included in the final analysis. Players' level included: amateur, youth, semi-professional, professional and elite players. All playing positions were considered, including goalkeepers. Six different global position systems brands were used, with the majority measuring data at 10 Hz. Different thresholds and intensities were used in several papers. Lower acceleration and deceleration intensities occurred more often than higher intensities in all four categories.

CONCLUSION

Different exercises elicit different demands and small-sided games presented higher acceleration and deceleration demands than circuit training and other running based drills. Furthermore, manipulating drills variables, as reducing or increasing number of players in small-sided games increase or decrease demands, respectively. Additionally, wide playing positions, such as fullbacks, are generally exposed to higher acceleration and deceleration demands. From a planning point of view, acceleration and deceleration demands decrease as match day approaches.

Biomechanical and Neuromuscular Performance Requirements of Horizontal Deceleration: A Review with Implications for Random Intermittent Multi-Directional Sports

Rapid horizontal accelerations and decelerations are crucial events enabling the changes of velocity and direction integral to sports involving random intermittent multi-directional movements. However, relative to horizontal acceleration, there have been considerably fewer scientific investigations into the biomechanical and neuromuscular demands of horizontal deceleration and the qualities underpinning horizontal deceleration performance. Accordingly, the aims of this review article are to: (1) conduct an evidence-based review of the biomechanical demands of horizontal deceleration and (2) identify biomechanical and neuromuscular performance determinants of horizontal deceleration, with the aim of outlining relevant performance implications for random intermittent multi-directional sports. We highlight that horizontal decelerations have a unique ground reaction force profile, characterised by high-impact peak forces and loading rates. The highest magnitude of these forces occurs during the early stance phase (< 50 ms) and is shown to be up to 2.7 times greater than those seen during the first steps of a maximal horizontal acceleration. As such, inability for either limb to tolerate these forces may result in a diminished ability to brake, subsequently reducing deceleration capacity, and increasing vulnerability to excessive forces that could heighten injury risk and severity of muscle damage. Two factors are highlighted as especially important for enhancing horizontal deceleration ability: (1) braking force control and (2) braking force attenuation. Whilst various eccentric strength qualities have been reported to be important for achieving these purposes, the potential importance of concentric, isometric and reactive strength, in addition to an enhanced technical ability to apply braking force is also highlighted. Last, the review provides recommended research directions to enhance future understanding of horizontal deceleration ability.

Neuromuscular Fatigue in Cerebral Palsy Football Players after a Competitive Match According to Sport Classification and Playing Position

This study aimed to determine the rated perceived exertion (RPE) and match load (RPE-ML) to compare pre-post-match vertical jump (VJ) capacity according to cerebral palsy (CP) players’ sport classes (i.e., FT1−FT3) and playing positions and to explore whether the neuromuscular performance variation is associated with the internal load of para-footballers with CP. Fifty-six male para-footballers performed two VJ tests before and immediately after a competitive CP football match, followed by measurements of the players’ RPE and RPE-ML. There were no significant differences (p > 0.05) in the pairwise comparisons for RPE and RPE-ML according to sport classes and playing position. A significant reduction in the VJ performance was found for each player sport class and playing position in squat jump (SJ) (p < 0.01; 0.24 < dg < 0.58) and countermovement jump (CMJ) (p < 0.05; 0.22 < dg < 0.45). Regarding the pairwise comparisons, players with the minimal impairment criteria (FT3) obtained higher deficit scores during SJ than those belonging to the FT1 and FT2 (p = 0.003; 1.00 < dg < 1.56). Defenders experienced the lowest performance compared to midfielders and attackers in SJ performance (p = 0.027; 0.94 < dg < 1.28). Significant correlations were obtained between ΔSJ or ΔCMJ and RPE or RPE-ML (r = −0.58 to −0.75; p < 0.001). These findings provide novel information supporting the notion that fatigue induced after a competitive match causes notable impairments in VJ performance differentiated according to sport class and playing position in para-footballers with CP.

The Use of Wearable Sensors for Preventing, Assessing, and Informing Recovery from Sport-Related Musculoskeletal Injuries: A Systematic Scoping Review

Wearable technologies are often indicated as tools that can enable the in-field collection of quantitative biomechanical data, unobtrusively, for extended periods of time, and with few spatial limitations. Despite many claims about their potential for impact in the area of injury prevention and management, there seems to be little attention to grounding this potential in biomechanical research linking quantities from wearables to musculoskeletal injuries, and to assessing the readiness of these biomechanical approaches for being implemented in real practice. We performed a systematic scoping review to characterise and critically analyse the state of the art of research using wearable technologies to study musculoskeletal injuries in sport from a biomechanical perspective. A total of 4952 articles were retrieved from the Web of Science, Scopus, and PubMed databases; 165 were included. Multiple study features-such as research design, scope, experimental settings, and applied context-were summarised and assessed. We also proposed an injury-research readiness classification tool to gauge the maturity of biomechanical approaches using wearables. Five main conclusions emerged from this review, which we used as a springboard to propose guidelines and good practices for future research and dissemination in the field.

Variation in Physical Performance of Futsal Players During Congested Fixtures

PURPOSE

To investigate the match-to-match variation of physical performance during official congested fixtures in elite futsal players.

METHODS

Physical performance was measured by external and internal load metrics in 12 elite male futsal players. Two periods with 3 matches within 4 days were analyzed. The variation in physical performance of the players during matches was analyzed using the latent growth curve modeling that estimated interindividual and intraindividual growth paths.

RESULTS

Playing time had a significant effect on physical performance growth with significant paths of interindividual and intraindividual variability. Players who competed for more time revealed lower initial levels (ie, first match) of total distance covered (β = -0.62), high-speed running (β = -0.18), accelerations (β = -0.31), decelerations (β = -0.44), and session rate of perceived exertion (β = 0.81) than players who competed for less time (P < .05). In addition, players who competed for more time revealed higher increases in total distance covered (β = 0.47), high-speed running (β = 0.16), and session rate of perceived exertion (β = 0.66) and lower increases in accelerations (β = -0.21) and decelerations (β = -0.58) than players who competed for less time from the first to the third match (P < .05).

CONCLUSIONS

Congested fixtures did not affect physical performance in elite futsal players. Playing time showed to be a key performance factor. There was a considerable heterogeneity in the responsiveness to physical performance over congested fixtures, suggesting an analysis of individual variability to evaluate real changes in match performance, training intensity, and workload.

Nutritional optimization for female elite football players-topical review

Women's football is an intermittent sport characterized by frequent intense actions throughout the match. The high number of matches with limited recovery time played across a long competitive season underlines the importance of nutritional strategies to meet these large physical demands. In order to maximize sport performance and maintain good health, energy intake must be optimal. However, a considerable proportion of female elite football players does not have sufficient energy intake to match the energy expenditure, resulting in low energy availability that might have detrimental physiologic consequences and impair performance. Carbohydrates appear to be the primary fuel covering the total energy supply during match-play, and female elite football players should aim to consume sufficient carbohydrates to meet the requirements of their training program and to optimize the replenishment of muscle glycogen stores between training bouts and matches. However, several macro- and micronutrients are important for ensuring sufficient energy and nutrients for performance optimization and for overall health status in female elite football players. The inadequacy of macro-and micronutrients in the diet of these athletes may impair performance and training adaptations, and increase the risk of health disorders, compromising the player's professional career. In this topical review, we present knowledge and relevant nutritional recommendations for elite female football players for the benefit of sports nutritionists, dietitians, sports scientists, healthcare specialists, and applied researchers. We focus on dietary intake and cover the most pertinent topics in sports nutrition for the relevant physical demands in female elite football players as follows: energy intake, macronutrient and micronutrient requirements and optimal composition of the everyday diet, nutritional and hydration strategies to optimize performance and recovery, potential ergogenic effects of authorized relevant supplements, and future research considerations.

The Effects of Successive Soccer Matches on the Internal Match Load, Stress Tolerance, Salivary Cortisol and Jumping Performance in Youth Soccer Players

The study aim was to analyze the effects of successive matches on the internal match load, stress tolerance, salivary cortisol concentration and countermovement vertical jump height in twelve youth soccer players (16.6 ± 0.5 yr; 175 ± 8 cm; 65 ± 8 kg) who performed four official matches within a four day-period with a 24-h recovery interval between the matches. The internal match load, monotony index and competitive strain, as well as stress tolerance were examined. Saliva samples were collected and countermovement vertical jump height was assessed 60 min pre and 30 min post each match; delta of salivary cortisol and countermovement vertical jump height for each match were analyzed. Salivary cortisol was analyzed using an enzyme-linked immunosorbent assay. The results of ANOVA with repeated measures showed no differences between matches for the internal match load (p > 0.05). The scores of the monotony index and competitive strain were 4.3 (±2.3) and 8104 (±6795) arbitrary units, respectively. There was no difference for stress tolerance between matches (p > 0.05). Delta values of salivary cortisol were not different among the assessed matches (F_(3,33) = 1.397, p = 0.351, η²: 0.09); however, delta of countermovement vertical jump height decreased from match 1 to match 4 (F_(3,33) = 8.64, p < 0.001, η²: 0.44). The current findings suggest that participating in four successive matches, with 24-h of recovery in between, may not lead to changes in stress tolerance and salivary cortisol of youth players, but it may induce a decrease in players' jumping performance after the fourth match.

Seasonal Changes and Relationships in Training Loads, Neuromuscular Performance, and Recovery and Stress State in Competitive Female Soccer Players

Background: The purpose of this study was to examine seasonal changes in training load (TL), neuromuscular performance, subjective recovery, and stress state, and to investigate the relationships between acute and chronic TL and neuromuscular performance in competitive female soccer players.

Methods: Nine competitive female soccer players (20.0 ± 1.7 years; 60.3 ± 6.3 kg; 164.0 ± 5.8 cm) completed the Short Recovery and Stress Scale and the countermovement jump (CMJ) with polyvinyl chloride pipe (CMJ0) and 20 kg barbell (CMJ20) at 2–3 h before 1st match (NC₁), 6th match (NC₂), 9th match (C₁), and 15th match (C₂) of the competitive season. TL included total distance, high-speed running, and PlayerLoad. Acute and chronic TL was calculated by using the average of 2 days (D₂), 7 days (D₇), and 21 days (D₂₁) prior to four different match play.

Results: Significant decreases were found from NC₁ to C₁ in D₇ total distance [p = 0.03, Cohen's effect size (d_z) = 1.40]. D₇ total distance and PlayerLoad significantly decreased from NC to C₁ and C₂ (p = 0.001–0.01, d_z = 1.40–1.72). Significant increases were observed from NC₁ to C₁ in CMJ0 jump height (p = 0.03, d_z = 1.40), (p = 0.021, d_z = 1.44), and peak power (p = 0.03, d_z = 1.32). Significant negative correlations were observed for D₇ total distance and CMJ0 jump height (p = 0.02, r = 0.79) and peak power (p = 0.03, r = 0.71) at C₂, while significant positive correlations were observed at C₁ for D₇ PlayerLoad and CMJ0 jump height (p = 0.02, r = 0.80).

Conclusion: Polyvinyl chloride pipe (CMJ0) jump height and peak power may increase from preseason to the midcompetitive season. Seasonal variations may affect the relationships between D₇ TL and CMJ0 performance.

Relationship Between Explosive Strength Capacity of the Knee Muscles and Deceleration Performance in Female Professional Soccer Players

The present study aimed to investigate the relationship between linear deceleration performance and explosive strength capacity of the knee muscles. Fourteen female professional soccer players completed the maximal sprint deceleration tests and knee flexor (KF) and knee extensor (KE) isokinetic concentric (240° and 60°.s⁻¹) and eccentric contractions (30°.s⁻¹). Linear deceleration performance was evaluated from horizontal breaking force (F_H), power (P_H), and impulse (I_H) during a maximal linear deceleration. The peak torque (PT) of KF and KE, PT ratio between KF and KE (conventional and functional H/Q ratio), rate of torque development (RTD) for each muscle group, and RTD between KF and KE (RTD H/Q) were extracted from the isokinetic contractions. Pearson’s correlation coefficients revealed that the eccentric (30°.s⁻¹) and concentric (60°.s⁻¹, 240°.s⁻¹) KE peak torque, and the concentric KF peak torque (240°.s⁻¹) were significantly correlated with F_H, P_H, and I_H (−0.75<r<−0.54). Moreover, a significant correlation was found between KE RTD during eccentric contraction and F_H, P_H, and I_H (−0.63<r<−0.54). Besides, a significant correlation was observed between RTD H/Q at 60°.s⁻¹ and P_H, I_H (−0.61<r<−0.57). No significant relationship was observed between the H/Q ratio, KF RTD and deceleration performance. These main findings indicated the importance of the ability to quickly produce high KE eccentric torque, contributing to braking force production. Meanwhile, RTD H/Q should be assessed for its essential role in knee joint dynamic stability and can be a relevant index to determine deceleration performance.

The Effect of High-Intensity Accelerations and Decelerations on Match Outcome of an Elite English League Two Football Team

Objectives: Previous research has highlighted the frequency of high-intensity accelerations and decelerations in elite football. The influence of these actions on match performance outcomes has not been established. The aim of the present study was to identify the influence of high-intensity accelerations and decelerations on match performance outcomes (i.e., win, draw, lost). Comparisons were also made between team and positional high-intensity accelerations and decelerations recorded within the games. Methods: 26 elite outfield footballers from an elite English Football League (EFL) Two team completed the present study. Global Positioning System (GPS) technology was utilised to quantify high-intensity accelerations and decelerations during 45 games in a competitive season. Magnitude analysis and the effects of results, positions and fixture periods were observed. Results: Significant effects of results, periods and positions were observed (p ≤ 0.05), with the highest outputs observed in games won. Positionally, fullbacks and centre forwards in a 4–3–3 formation exhibited the greatest frequency of high-intensity accelerations and decelerations. Very large differences were observed between the frequency of high-intensity decelerations compared to accelerations in games won (g = 2.37), drawn (g = 2.99) and lost (g = 3.59). The highest team frequencies of high-intensity accelerations (n = 3330) and decelerations (n = 6482) were completed in games won. Conclusions: The frequency of high-intensity accelerations and decelerations has a significant impact on match performance outcomes in an elite English League Two football team. Consideration needs to be given to specific conditioning and recovery strategies to optimise high-intensity acceleration and deceleration performance in games. Caution should be taken as these findings are representative of one team within the EFL.

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.

Win, Draw, or Lose? Global Positioning System-Based Variables' Effect on the Match Outcome: A Full-Season Study on an Iranian Professional Soccer Team

The aim of the study was to determine the between-match and between-halves match variability of various Global Positioning System (GPS) variables and metabolic power average (MPA) in competitions, based on the match results obtained by professional soccer players over a full season. Observations on individual match performance measures were undertaken on thirteen outfield players competing in the Iranian Premier League. The measures selected for analysis included total duration, accelerations in zones (AccZ1, 2, and 3), decelerations in zones (DecZ1, 2, and 3), and MPA collected by the Wearable Inertial Measurement Unit (WIMU). The GPS manufacturer set the thresholds for the variables analyzed as follows: AccZ1 (<2 m·s⁻²); AccZ2 (2 to 4 m·s⁻²); AccZ3 (>4 m·s⁻²); DecZ1 (<−2 m·s⁻²); DecZ2 (−2 to −4 m·s⁻²); DecZ3 (>−4 m·s⁻²). The results revealed significant differences between wins and draws for the duration of the match and draws compared to wins for the first- half duration (p ≤ 0.05; ES = 0.36 [−0.43, 1.12]), (p ≤ 0.05; ES = −7.0 [−8.78, −4.78], respectively. There were significant differences on AccZ1 during the first-half between draws and defeats (p ≤ 0.05; ES = −0.43 [−1.32, 0.46]), for AccZ3 in the second-half between draws and defeats (p ≤ 0.05; ES = 1.37 [0.48, 2.25]). In addition, there were significant differences between wins and draws (p ≤ 0.05; ES = 0.22 [−0.62, 1.10]), and wins and defeats for MPA in the first- half (p ≤ 0.05; ES = 0.34 [−0.65, 1.22]). MPA showed further differences between draws and defeats in the second- half (p ≤ 0.05; ES = 0.57 [−0.22, 1.35]). Descriptive analysis revealed differences between the first and second half for wins in AccZ2 (p = 0.005), DecZ2 (p = 0.029), and MPA (p = 0.048). In addition, draws showed significant differences between the first and second half in duration, AccZ1, AccZ2, and DecZ2 (p = 0.008), (p = 0.017), (p = 0.040), and (p = 0.037) respectively. Defeats showed differences between the first and second half in AccZ1, AccZ3, and MPA (p = 0.001), (p = 0.018), and (p = 0.003) respectively. In summary, the study reveals large variations between the match duration, accelerometer variables, and MPA both within and between matches. Regardless of the match outcome, the first half seems to produce greater outputs. The results should be considered when performing a half-time re-warm-up, as this may be an additional factor influencing the drop in the intensity markers in the second half in conjunction with factors such as fatigue, pacing strategies, and other contextual variables that may influence the results.

Associations between maximal strength, sprint, and jump height and match physical performance in high-level female football players

Studies on females' decisive physical components to physical match-play performance are sparse and only emphasize endurance tests. Thus, the influence of maximal strength and power on physical performance during match-play is currently unknown. The aim of this study was to assess the association between one repetition maximum (1RM) half squat strength, 5-, 10-, and 15-m sprint times, countermovement jump (CMJ) height, and physical high-intensity match-play performance in high-level female football players. Thirty-seven female high-level football players completed 1-2 football matches with physical performance measured by local positioning tracking. Correlations were assessed between physical match-play performance variables (total distance covered, running distance, high-intensity running distance, sprinting distance as well as acceleration and deceleration counts, and peak speed) and laboratory tests (half squat 1RM, 15-m sprint, and CMJ). We found no correlation between 1RM and physical match-play performance. Further, 10-m- and 15-m sprint time (r = -0.56, r = -0.56, p < 0.001) and CMJ jump height (r = 0.50, p < 0.01) strongly correlated with peak match speed. Further, there was a moderate correlation between 15-m sprint time and ACC (r = -0.43, p < 0.05). 5-m sprint time did not correlate with physical match-play performance. Laboratory-based sprint and jump performance, but not maximal half squat strength, showed moderate to large correlations with high-intensity physical match-play performance measures in high-level female football players.

Key load indicators and load variability in professional soccer players: a full season study

The aims of this study were to 1) determine the key load indicators in professional soccer through principal component analysis (PCA); and 2) analyse the load variability of each training and match day within the microcycle considering the principal components. Data from 111 load variables were collected using tracking systems in both training and match days (MD). The results showed that 7 variables, which belonged to the first two components of the PCA, explained 80.3% of total variance. Specifically, these variables were Metabolic power, total of steps, Fourier transform (FFT) duration, deceleration distance covered (2-3 m/s²), total of running actions (12-18 km/h; 21-24 km/h), and distance covered (6-12 km/h). Regarding the analysis of the load variability of each training and match day within the microcycle, the lowest load variability was observed in -1MD. Also, a great load variability in +1MD with significant differences compared to -5MD (p<0.001; d=0.49) and -4MD (p=0.01; d=0.26) was found. This study suggests the use of the PCA in the context of team sports to reduce the large number of variables, which are daily managed by strength and conditioning coaches, in addition to the analysis of load variability of each training and match day within the microcycle.

Motion Analysis of Match Play in U14 Male Soccer Players and the Influence of Position, Competitive Level and Contextual Variables

This study aimed to investigate match running performance in U14 male soccer players in Norway, and the influence of position, competitive level and contextual factors on running performance. Locomotion was monitored in 64 different U14 players during 23 official matches. Matches were played at two different competitive levels: U14 elite level (n = 7) and U14 sub-elite level (n = 16). The inclusion criterion was completed match halves played in the same playing position. The variables’ influence on match running performance was assessed using mixed-effect models, pairwise comparisons with Bonferroni correction, and effect size. The results showed that the U14 players, on average, moved 7645 ± 840 m during a match, of which 1730 ± 681 m (22.6%) included high-intensity running (HIR, 13.5–18.5 km·h⁻¹) and sprinting (>18.5 km·h⁻¹). Wide midfielders (WM) and fullbacks (FB) covered the greatest sprint distance (569 ± 40 m) and, in addition to the centre midfield position (CM), also covered the greatest total distance (TD) (8014 ± 140 m) and HIR distance (1446 ± 64 m). Centre forwards (CF) performed significantly more accelerations (49.5 ± 3.8) compared other positions. TD (7952 ± 120 m vs. 7590 ± 94 m) and HIR (1432 ± 57 m vs. 1236 ± 43 m) were greater in U14 elite-level matches compared with sub-elite matches. Greater TD and sprint distances were performed in home matches, but, on the other hand, more accelerations and decelerations were performed in matches played away or in neutral locations. Significantly higher TD, HIR and sprinting distances were also found in lost or drawn matches. In conclusion, physical performance during matches is highly related to playing position, and wide positions seem to be the most physically demanding. Further, competitive level and contextual match variables are associated with players’ running performance.

The Quantification of Acceleration Events in Elite Team Sport: a Systematic Review

BACKGROUND

Wearable tracking devices are commonly utilised to quantify the external acceleration load of team sport athletes during training and competition. The ability to accelerate is an important attribute for athletes in many team sports. However, there are many different acceleration metrics that exist in team sport research. This review aimed to provide researchers and practitioners with a clear reporting framework on acceleration variables by outlining the different metrics and calculation processes that have been adopted to quantify acceleration loads in team sport research.

METHODS

A systematic review of three electronic databases (CINAHL, MEDLINE, SPORTDiscus), was performed to identify peer-reviewed studies that published external acceleration load in elite team sports during training and/or competition. Articles published between January 2010 and April 2020 were identified using Boolean search phrases in relation to team sports (population), acceleration/deceleration (comparators), and competition and/or training (outcome). The included studies were required to present external acceleration and/or deceleration load (of any magnitude) from able-bodied athletes (mean age ≥ 18 years) via wearable technologies.

RESULTS

A total of 124 research articles qualified for inclusion. In total, 113/124 studies utilised GPS/GNSS technology to outline the external acceleration load of athletes. Count-based metrics of acceleration were predominant of all metrics in this review (72%). There was a lack of information surrounding the calculation process of acceleration with 13% of studies specifying the filter used in the processing of athlete data, whilst 32% outlined the minimum effort duration (MED). Markers of GPS/GNSS data quality, including horizontal dilution of precision (HDOP) and the average number of satellites connected, were outlined in 24% and 27% of studies respectively.

CONCLUSIONS

Team sport research has predominantly quantified external acceleration load in training and competition with count-based metrics. Despite the influence of data filtering processes and MEDs upon acceleration, this information is largely omitted from team sport research. Future research that outlines acceleration load should present filtering processes, MEDs, HDOP, and the number of connected satellites. For GPS/GNSS systems, satellite planning tools should document evidence of available satellites for data collection to analyse tracking device performance. The development of a consistent acceleration filtering method should be established to promote consistency in the research of external athlete acceleration loads.

Comparison of Official and Friendly Matches through Acceleration, Deceleration and Metabolic Power Measures: A Full-Season Study in Professional Soccer Players

Soccer is a popular team sport and highly demanding activity that requires high effort and long-term training plans. The goals of this study were to compare the accelerations, decelerations and metabolic power between official and friendly full matches, between the first and second halves of the matches, and between both halves of official and friendly matches. Twelve professional soccer players (age, 28.6 ± 2.7 years; height, 182.1 ± 8.6 cm; body mass, 75.3 ± 8.2 kg; BMI, 22.6 ± 0.7 kg/m²) participated in this study. A total of 33 official and 10 friendly matches were analyzed from the Iranian Premier League. All matches were monitored using GPSPORTS systems Pty Ltd. The following variables were selected: total duration of the matches, metabolic power, accelerations Zone1 (<2 m·s^-2) (AccZ1), accelerations Zone2 (2 to 4 m·s^-2) (AccZ2), accelerations Zone3 (>4 m·s^-2) (AccZ3), decelerations Zone1 (<-2 m·s^-2) (DecZ1), decelerations Zone2 (-2 to -4 m·s^-2) (DecZ2) and decelerations Zone3 (>-4 m·s^-2) (DecZ3). The major finding was shown in metabolic power, where higher values occurred in friendly matches (p < 0.05 with small effect size). Furthermore, total duration, AccZ3, DecZ1, DecZ2, and DecZ3 were revealed to be higher in official matches, while AccZ1 and AccZ2 were higher in friendly matches. The second half of the official matches revealed higher values for total duration compared to friendly matches (p < 0.05, moderate effect size). In conclusion, this study observed higher values of metabolic power in friendly matches compared to official matches. AccZ3, DecZ1, DecZ2, and DecZ3 were higher in official matches, while AccZ1 and AccZ2 were higher in friendly matches.

Volume and Intensity of Locomotor Activity in International Men's Field Hockey Matches Over a 2-Year Period

The locomotor demands of international men's field hockey matches were investigated across positions (DEF, MID, FWD) and playing quarters. Volume (i.e., total values) and intensity (i.e., relative to playing time) data were collected using 10-Hz GPS/100-Hz accelerometer units from the #11 world-ranked (WR) team, during 71 matches, against 24 opponents [WR 12 ± 11 (range, 1–60)]. Mean ± SD team total distance (TD) was 4,861 ± 871 m, with 25% (1,193 ± 329 m) “high-speed running” (>14.5 km h⁻¹) and 8% (402 ± 144 m) “sprinting” (>19.0 km h⁻¹). Reduced TD (range, −3 to 4%) and average speed (range, −3.4 to 4.7%) occurred through subsequent quarters, vs. Q1 (p < 0.05). A “large” negative relationship (r = −0.64) was found between playing duration and average speed. Positional differences (p < 0.05) were identified for all volume metrics including; playing duration (DEF, 45:50 ± 8:00 min; MID, 37:37 ± 7:12 min; FWD, 33:32 ± 6:22 min), TD (DEF, 5,223 ± 851 m; MID, 4,945 ± 827 m; FWD, 4,453 ± 741 m), sprinting distance (DEF, 315 ± 121 m; MID, 437 ± 144 m; FWD, 445 ± 129 m), and acceleration efforts (>2 m s⁻²; DEF, 48 ± 12; MID, 51 ± 11; FWD, 50 ± 14). Intensity variables similarly revealed positional differences (p < 0.05) but with a different pattern between positions; average speed (DEF, 115 ± 10 m min⁻¹; MID, 132 ± 10 m min⁻¹; FWD, 134 ± 15 m min⁻¹), sprinting (DEF, 7 ± 3 m min⁻¹; MID, 12 ± 4 m min⁻¹; FWD, 14 ± 4 m min⁻¹), and accelerations (DEF, 1.1 ± 0.3 n min⁻¹; MID, 1.4 ± 0.2 n min⁻¹; FWD, 1.5 ± 0.3 n min⁻¹). Physical outputs reduced across playing quarters, despite unlimited substitutions, demonstrating the importance of optimizing physical preparation prior to international competition. Volume and intensity data highlight specific positional requirements, with forwards displaying shorter playing durations but greater high-intensity activities than defenders.

Somatic Characteristics and Special Motor Fitness of Young Top-Level Polish Table Tennis Players

In the present study, we aimed to identify the impact of chosen anthropometric measurements on the special physical fitness of elite junior table tennis players at different stages of sport training. A total of 87 table tennis players aged 13.4 ± 1.74 years (43.7% girls and 56.3% boys) from two Polish teams were analyzed. The anthropometry measurements included height, sitting height, body weight, arm span, humerus and femur breadths, five skinfold thicknesses, and five girths were assessed. Participants’ somatotypes were also calculated using the Heath–Carter method as well as body mass index (BMI), which was constructed using the lambda, mu, sigma (LMS) method. Body composition via a bioelectric impedance analysis was also analyzed. The level of special fitness of athletes was determined using tests from the Table Tennis Specific Battery Test, assessing reaction and displacement speeds. Mesomorphic (4.1) and ectomorphic (3.8) profiles were registered for boys and girls, respectively. Boys achieved higher scores than girls for almost all variables, with the exception of ectomorphic somatotype (p = 0.274), skinfold triceps (p = 0.444), and calf skinfold medial (p = 0.609). The relationship between the body height, thickness of the skinfolds of the triceps and suprailiac, biceps, and waist circumference and arm span in all three motor tests was observed, simultaneously significantly higher results were obtained by competitors at the specialist stage of training. Knowledge of the somatic and motor characteristics of young athletes can help coaches in creating a specific training program for improved health and performance, taking into consideration the athletes’ biological development, potential, and pre-disposition.