Plyometric Jump Training Effects on Maximal Strength in Soccer Players: A Systematic Review with Meta-analysis of Randomized-Controlled Studies.

BACKGROUND: Maximal strength may contribute to soccer players' performance. Several resistance training modalities offer the potential to improve maximal strength. During recent years, a large number of plyometric jump training (PJT) studies showed evidence for maximal strength improvements in soccer players. However, a comprehensive summary of the available data is lacking. OBJECTIVE: To examine the effects of PJT compared with active, passive or intervention controls on the maximal strength of soccer players, irrespective of age, sex or competitive level. METHODS: To perform a systematic review with meta-analysis following PRISMA 2020. Three electronic databases (PubMed, Web of Science, and SCOPUS) were systematically searched. Studies published from inception until March 2023 were included. A PICOS approach was used to rate studies for eligibility. The PEDro scale was used to assess risk of bias. Meta-analyses were performed using the DerSimonian and Laird random-effects model if ≥ 3 studies were available. Moderator and sensitivity analyses were performed, and meta-regression was conducted when ≥ 10 studies were available for a given comparison. We rated the certainty of evidence using GRADE. RESULTS: The search identified 13,029 documents, and from these 30 studies were eligible for the systematic review, and 27 for the meta-analyses. Overall, 1,274 soccer players aged 10.7-25.0 years participated in the included studies. Only one study recruited females. The PJT interventions lasted between 5 and 40 weeks (median = 8 weeks), with 1-3 weekly sessions. Compared to controls, PJT improved maximal dynamic strength (18 studies, 632 participants [7 females], aged 12.7-24.5 y; effect size [ES] = 0.43, 95% confidence interval [CI] = 0.08-0.78, p = 0.017, impact of statistical heterogeneity [I2] = 77.9%), isometric strength (7 studies; 245 participants, males, aged 11.1-22.5 y; ES = 0.58, 95% CI = 0.28-0.87, p < 0.001, I2 = 17.7%), and isokinetic peak torque (5 studies; 183 participants, males, aged 12.6-25.0 y; ES = 0.51, 95% CI = 0.22-0.80, p = 0.001, I2 = 0.0%). The PJT-induced maximal dynamic strength changes were independent of participants' age (median = 18.0 y), weeks of intervention (median = 8 weeks), and total number of training sessions (median = 16 sessions). The certainty of evidence was considered low to very low for the main analyses. CONCLUSIONS: Interventions involving PJT are more effective to improve maximal strength in soccer players compared to control conditions involving traditional sport-specific training. Trial Registration The trial registration protocol was published on the Open Science Framework (OSF) platform in December 2022, with the following links to the project ( https://osf.io/rpxjk ) and to the registration ( https://osf.io/3ruyj ).

Comparative Effects of Two High-Intensity Intermittent Training Programs on Sub-Elite Male Basketball Referees' Fitness Levels.

This study aimed to compare the effects of an 8-week short-term training program, comprising repeated sprints or running-based high-intensity intermittent training (HIIT), on the aerobic fitness and repeated sprint ability (RSA) performance of sub-elite basketball referees. Twenty male referees participated in supervised training sessions twice a week. They were randomly assigned to either the RSA-based group (RSAG) or the running-based HIIT group (HIITG). The RSAG conducted 3-4 sets of 8 × 20-m all-out sprints, while the HIITG performed 2-3 sets of 6 × 20-s runs at 90% of their maximal velocity achieved in the 30-15 intermittent fitness test (30-15IFT). Referees underwent a graded exercise test on a treadmill, the 30-15IFT, and an RSA test before and after the training program. Both groups showed significant improvement (~3%) in the fastest (22.6 ± 1.4 vs. 23.4 ± 1.7 and 22.0 ±1.9 vs. 22.4 ± 1.7 km·h-1 in RSAG and HIITG, respectively) and mean (21.5 ± 1.2 vs. 22.4 ± 1.4 and 21.3 ± 1.8 vs. 21.7 ± 1.6 km·h-1 in RSAG and HIITG, respectively) sprint velocity of the RSA test (p < 0.05). Moreover, positive changes (p < 0.05) were observed in the 30-15IFT maximal velocity (18.6 ± 1.1 vs. 19.3 ± 1.0 and 19.4 ± 0.9 vs. 20.5 ± 0.9 km·h-1 in RSAG and HIITG, respectively). In conclusion, an 8-week training intervention using either RSA or running-based HIIT led to similar improvements in referees' RSA performance and specific aerobic fitness measures. These findings could assist in devising tailored training programs for basketball referees.

Validation of ActiGraph and Fitbit in the assessment of energy expenditure in Huntington's disease.

BACKGROUND: Consumer and research activity monitors have become popular because of their ability to quantify energy expenditure (EE) in free-living conditions. However, the accuracy of activity trackers in determining EE in people with Huntington's Disease (HD) is unknown. RESEARCH QUESTION: Can the ActiGraph wGT3X-B or the Fitbit Charge 4 accurately measure energy expenditure during physical activity, in people with HD compared to Indirect Calorimetry (IC) (Medisoft Ergo Card)? METHODS: We conducted a cross-sectional, observational study with fourteen participants with mild-moderate HD (mean age 55.7 ± 11.4 years). All participants wore an ActiGraph and Fitbit during an incremental test, running on a treadmill at 3.2 km/h and 5.2 km/h for three minutes at each speed. We analysed and compared the accuracy of EE estimates obtained by Fitbit and ActiGraph against the EE estimates obtained by a metabolic cart, using with Intra-class correlation (ICC), Bland-Altman analysis and correlation tests. RESULTS: A significant correlation and a moderate reliability was found between ActiGraph and IC for the incremental test (r = 0.667)(ICC=0.633). There was a significant correlation between Fitbit and IC during the incremental test (r = 0.701), but the reliability was poor at all tested speeds in the treadmill walk. Fitbit significantly overestimated EE, and ActiGraph underestimated EE compared to IC, but ActiGraph estimates were more accurate than Fitbit in all tests. SIGNIFICANCE: Compared to IC, Fitbit Charge 4 and ActiGraph wGT3X-BT have reduced accuracy in estimating EE at slower walking speeds. These findings highlight the need for population-specific algorithms and validation of activity trackers.

Cómo estimar la composición corporal en la enfermedad de Huntington. Estudio transversal y observacional con bioimpedancia de múltiples frecuencias / How to estimate body composition in Huntington’s disease. A cross-sectional, observational study using multiple frequencies bioimpedance

Introducción La enfermedad de Huntington (EH) es un trastorno raro neurodegenerativo. La información fiable del estado nutricional, especialmente de la composición corporal, es crítica en clínica y en investigación. La facilidad de aplicación y portabilidad del análisis de la bioimpedancia de múltiples frecuencias (mfBIA) la convierten en una herramienta atractiva para medirla, pero se desconoce su precisión en la EH. Objetivo Evaluar la precisión del mfBIA frente a la absorciometría dual de rayos X (DEXA) en la EH. Pacientes y métodos Estudio transversal, observacional y unicéntrico. La EH se midió con la subescala motora de la escala unificada de valoración de la EH y con la capacidad funcional total. La composición corporal se valoró según la masa libre de grasa (MLG), la masa grasa (MG), el índice de masa libre de grasa (IMLG) y el índice de masa grasa (IMG). Se utilizó el coeficiente de correlación intraclase con intervalos de confianza al 95% y estimaciones de sesgo mediante gráficos de Bland-Altman. Resultados Se incluyó a 16 pacientes, siete hombres y nueve mujeres, con edad media de 58,5 (32-68) años, capacidad funcional total de 10 (3-13) y escala unificada de valoración de la EH de 31 (7-85). La fiabilidad era alta entre el mfBIA y la DEXA para el IMLG en hombres, 0,88 (intervalo de confianza al 95%: 0,17-0,98), y mujeres, 0,9 (intervalo de confianza al 95%: 0,61-0,98); y para el IMG en hombres, 0,97 (intervalo de confianza al 95%: 0,83-0,99), y mujeres, 0,91 (intervalo de confianza al 95%: 0,68-0,98). El mfBIA sobreestimó ligeramente la MLG, la MG, el IMG y el IMLG en los hombres, pero subestimó el IMLG en las mujeres. Conclusiones El mfBIA es un método fácil de usar, seguro, no invasivo y preciso para medir la composición corporal y el estado nutricional en pacientes con EH leve-moderada. (AU)

INTRODUCTION Huntington´s disease (HD) is a rare neurodegenerative disorder. Reliable information about nutritional status, especially body composition from individuals with HD is critical for clinical care and research. The ease of application and portability of multiple frequencies bioelectrical impedance analysis (mfBIA) make it an attractive tool for measuring body composition, but its accuracy in HD is unknown. AIM To evaluate the accuracy of mfBIA vs. Dual X-ray absorptiometry (DEXA) in HD. PATIENTS AND METHODS Cross-sectional, observational, and single-center study. HD severity was measured using motor subscale of the unified Huntington´s disease rating scale (m-UHDRS) and the total functional capacity (TFC). Body composition was measured in terms of fat-free mass (FFM), fat mass (FM), fat-free mass index (FFMI), and fat mass index (FMI). Using Bland-Altman plots, we analyzed reliability between DEXA and mfBIA using the Intraclass Correlation Coefficient with 95% confidence intervals (CI) and bias estimates for all. RESULTS We included 16 patients with HD, 7 men, and 9 women, median age of 58.5 (32;68) years, TFC: 10 (3;13), and m-UHDRS: 31 (7;85). The reliability between mfBIA and DEXA were high for FFMI in men: 0.88 (95% CI 0.17-0.98), and women: 0.90 (95% CI 0.61- 0.98); for FMI, men: 0.97 (95% CI 0.83-0.99), and women: 0.91 (95% CI 0.68-0.98). Compared to DEXA, mfBIA slightly overestimated FFM, FM, FMI and FFMI in men and underestimated FFMI in women. CONCLUSIONS mfBIA is an easy-to-use, safe, non-invasive, accurate method for measuring body composition and nutritional status in patients with mild-moderate HD. (AU)

The discriminative, criterion, and longitudinal validity of small-sided games to assess physical fitness in female basketball players.

The validity of small-sided games (SSG) for assessing physical fitness was evaluated in 21 female basketball players from senior (n = 8), under-18 years (n = 6), and under-16 years (n = 7) age categories. Players underwent fitness testing (countermovement jump [CMJ], agility T-test, repeated-sprint ability (RSA) test, and Yo-Yo Intermittent Recovery Test [YYIRT1]) and 3vs3-SSG before and after a 6-week preseason. Player demands were monitored during SSG using local positioning system and heart rate technology. Regarding discriminative validity, senior players produced better CMJ, agility T-test, and YYIRT1 performance (p < 0.05, effect size [ES] = 1.72-2.25), and more distance and PlayerLoad (p < 0.05, ES = 1.53-2.47) during SSG than under-18 players following the preseason. For criterion validity, total distance and distance completing high-intensity decelerations during SSG were significantly (p < 0.05) correlated with CMJ (r = 0.44-0.66), YYIRT1 (r = 0.43-0.63), agility T-test (total distance only, r=-0.51), and RSA test performance (r=-0.49 to -0.52) among all players combined following the preseason. Regarding longitudinal validity, significantly better agility T-test and YYIRT1 performance (p ≤ 0.001, ES = 0.88-0.93) alongside lower heart rate during SSG (p = 0.001, ES = 0.88) were evident for all players combined following the preseason. These results partially support the validity of 3vs3-SSG to assess physical fitness in female basketball players.

Effect of Different Nonstarter Compensatory Strategies on Training Load in Female Soccer Players: A Pilot Study.

BACKGROUND: In soccer, the day of the week with the highest external load is match day (MD), with starters (>60 minutes per match) showing higher levels of physical fitness and seasonal high-intensity loading. It is necessary, therefore, to determine training strategies to reduce the differences between starters and nonstarters. The aim of this study was to analyze and compare the external load of different training compensatory strategies with match external load in female nonstarters. HYPOTHESIS: A strategy combining small-sided games (SSG) and running-based drills (RBD) would reproduce match demands, with RBD leading to greater high-intensity running and SSG leading to a greater number of accelerations and decelerations. STUDY DESIGN: Descriptive and comparative study. LEVEL OF EVIDENCE: Level 4. METHODS: The training and match external load of 14 female players belonging to the same reserve squad of a Spanish First Division Club (Liga Reto Iberdrola) was registered. In the first session after the match (MD+1), nonstarters (<60 minutes in the match) performed 1 of 3 different compensatory strategies: RBD, SSG, or a mixed intervention combining the previous strategies (RBD+SSG). Starters carried out a recovery session. RESULTS: A marked difference in load was observed between the compensatory training strategies and MD. In comparison with MD, RBD showed greater high-intensity and sprint distances and lower acceleration, SSG showed less high-intensity running and sprint distances, lower peak velocity, and greater acceleration, and RBD+SSG registered lower accelerations. In addition, nonstarters covered greater high-intensity running and sprint distances in RBD and achieved higher accelerations in SSG. CONCLUSION: RBD and SSG compensatory strategies could be recommended to nonstarter female soccer players in MD+1 to compensate for match external load deficits. CLINICAL RELEVANCE: This study provides comprehensive information on the compensatory exercises of female soccer players, which can be useful for strength and conditioning coaches when developing recovery strategies during a microcycle.

The effects of training based on Nordic hamstring and sprint exercises on measures of physical fitness and hamstring injury prevention in U19 male soccer players.

This study analysed the effects of a training program based on Nordic hamstring and sprint exercises on physical performance and hamstring injuries in young male soccer players. Forty-nine U19 players were randomly assigned to a control (CG; n = 26) or experimental group (EG; n = 23). Linear sprint and with change of direction (COD) were assessed before and after a 14-week training period. Hamstring injuries were collected during the intervention period. Between-groups analysis revealed differences in linear sprint performance (p = 0.012-0.001) in favour of the EG. Pre-to-post performance increased significantly in the EG for 20 m (effect size [ES] = -0.56) and 30 m (ES = -0.62) sprints, but a significant reduction in some COD parameters was observed (ES = 0.45-0.57). In CG, only a significant reduction in COD with dominant leg was found (ES = 0.63). Significant differences in injury burden in favour of the EG was reported such as (27.87 [CG] vs. 3.82 [EG] absence days/1000 h of exposure, rate ratio = 7.30, 95% CI 3.34-15.99). While injury incidence was not different between the EG and CG. These findings suggest that the training program implemented can improve sprint performance and reduce injury burden.

Accelerometer Cut-Points for Physical Activity Assessment in Adults with Mild to Moderate Huntington's Disease: A Cross-Sectional Multicentre Study.

Accelerometers can estimate the intensity, frequency, and duration of physical activity in healthy adults. Although thresholds to distinguish varying levels of activity intensity using the Actigraph wGT3X-B have been established for the general population, their accuracy for Huntington's disease (HD) is unknown. We aimed to define and cross-validate accelerometer cut-points for different walking speeds in adults with mild to moderate HD. A cross-sectional, multicentre, case-control, observational study was conducted with a convenience sample of 13 symptomatic ambulatory HD participants. The accelerometer was placed around the right hip, and a heart monitor was fitted around the chest to monitor heart rate variability. Participants walked on a treadmill at three speeds with light, moderate and vigorous intensities. Correlation and receiver operation curve analyses were performed between the accelerometer magnitude vector with relative oxygen and heart rate. Optimal cut-points for walking speeds of 3.2 km/h were ≤2852; 5.2 km/h: >2852 to ≤4117, and in increments until their maximum velocity: >4117. Our results support the application of the disease-specific cut-points for quantifying physical activity in patients with mild to moderate HD and promoting healthy lifestyle interventions.

Inter- and intra-microcycle external load analysis in female professional soccer players: A playing position approach.

This study analyzes the inter- and intra-differences in external load across the microcycle in professional female soccer players. External load during four consecutive microcycles (i.e., M1, M2, M3, and M4) and training sessions (i.e., MD-4, MD-3, MD-2, and MD-1) and a match day (i.e., MD) were registered in seventeen female professional soccer players (age: 26.3 ± 4.6 years; height: 166.3 ± 6.1 cm; body mass: 59.8 ± 6.8 kg; and body mass index: 21.6 ± 1.7 kg·m-2) who belonged to the same team in Spanish first division. A 10-Hz GPS that integrated a 100-Hz triaxial accelerometer was used to register external load. The results showed lower decelerations in M2 compared to M1 and M3 (p < 0.05), lower high-intensity distance (>16.0 km·h-1) in M3 vs. M2, and greater relative sprint distance (>21.0 km·min-1) in M4 vs. M1 and M3 (p < 0.05). MD-3 registered the highest load for all variables (p < 0.05). Forwards (FWs) performed (p < 0.05) significantly more sprints (meters and number > 21.0 km·h-1) than central midfielders (CMs) and central defenders (CDs) in MD-2 and MD. Both, fitness and conditioning staff should pay special attention to the external loads for each playing position in training sessions to optimize the training process.

The effects of defensive style and final game outcome on the external training load of professional basketball players.

This study aimed to analyse the influence of different contextual factors (i.e., defensive style and game outcome) on basketball players' external load during games-based drills using ultrawideband (UWB) technology. Fourteen male professional basketball players belonging to an elite reserve Spanish club (ACB) participated in this study. The games-based drills consisted of one bout of 10 min played 5vs5 in which players were instructed to use man-to-man defence (MMD) and/or zone defence (ZD). In addition, the final game outcome (i.e., winning or losing) of the game-based drill was registered. External load variables per minute were recorded: total distance covered, distance covered in different speed zones, distance covered while accelerating and decelerating, maximum speed, steps, jumps and player load. A two-way ANOVA with the Tukey post hoc test was used to assess the impact of defensive style and final game outcome and the interaction of both factors on the external load encountered by basketball players. No meaningful differences (unclear) were found in the external loads between playing with MMD and with ZD and between winning and losing teams except for greater distance at high-speed running (18.0-24.0 km·h-1) in winning teams (p < 0.05, ES = 0.68, moderate). A significant interaction between defensive style and final game outcome was found for high decelerations (> -2 m·s-2) (p = 0.041; ES = 0.70) and jumps (p = 0.037; ES = 0.68). These results could potentially help coaching staff in prescribing an appropriate workload during basketball-specific game-based drills, and ultimately enhance the match performance.

Caffeine Ingestion Improves Performance During Fitness Tests but Does Not Alter Activity During Simulated Games in Professional Basketball Players.

PURPOSE: To examine the effects of acute caffeine supplementation on physical performance during fitness testing and activity during simulated games in basketball players. METHODS: A double-blind, counterbalanced, randomized, crossover study design was followed. A total of 14 professional male basketball players ingested a placebo (sucrose) and caffeine (6 mg·kg-1 of body mass) in liquid form prior to completing 2 separate testing sessions. Each testing session involved completion of a standardized 15-minute warm-up followed by various fitness tests including 20-m sprints, countermovement jumps, Lane Agility Drill trials, and a repeated-sprint-ability test. Following a 20-minute recovery, players completed 3 × 7-minute 5-vs-5 simulated periods of full-court basketball games, each separated by 2 minutes of recovery. Local positioning system technology was used to measure player activity during games. Players completed a side-effects questionnaire 12 to 14 hours after testing. RESULTS: Players experienced significant (P < .05), moderate-very large (effect size = -2.19 to 0.89) improvements in 20-m sprint, countermovement jump, Lane Agility Drill, and repeated-sprint-ability performance with caffeine supplementation. However, external workloads completed during simulated games demonstrated nonsignificant, trivial-small (effect size = -0.23 to 0.12) changes between conditions. In addition, players reported greater (P < .05) insomnia and urine output after caffeine ingestion. CONCLUSIONS: Acute caffeine supplementation could be effective to improve physical performance during tests stressing fitness elements important in basketball. However, acute caffeine supplementation appears to exert no meaningful effects on the activity completed during simulated basketball games and may promote sleep disturbances and exert a diuretic effect when taken at 6 mg·kg-1 of body mass in professional players.

Influence of Different Small-Sided Game Formats on Physical and Physiological Demands and Physical Performance in Young Soccer Players.

ABSTRACT: Castillo, D, Rodríguez-Fernández, A, Nakamura, FY, Sanchez-Sanchez, J, Ramirez-Campillo, R, Yanci, J, Zubillaga, A, and Raya-González, J. Influence of different small-sided game formats on physical and physiological demands and physical performance in young soccer players. J Strength Cond Res 35(8): 2287-2293, 2021-The aim of this study was to quantify the acute impact of bout duration and individual interaction space on physical and physiological demands and on physical performance. Ten young male soccer players (age: 14.8 ± 0.6 years) from the same team playing in the National U-16 Division participated. Physical (total distance [TD]; distance covered at different speeds; and maximum velocity [Velmax]) and physiological (peak [HRpeak] and mean [HRmean] heart rate) parameters were collected for every bout during each small-sided game (SSG) format. Moreover, the effects of SSGs on horizontal jump (HJ) and 30-m sprint performances were evaluated. The SSG formats were composed of 6 players a side (including goalkeepers) and included 4 repetitions of 6 minutes in a space of 100 m2 (SSG1) or 200 m2 (SSG2) and 6 repetitions of 4 minutes in 100 m2 (SSG3) or 200 m2 (SSG4). The TD, the distance covered at different speeds, and Velmax were greater (p < 0.01, effect size [ES] = 1.25-5.95, large) in SSG2 and SSG4 than SSG1 and SSG3, respectively. Furthermore, the HRmean and HRpeak were lower (p < 0.05, ES = 1.53-2.23, large) during SSG3 than other SSGs. In addition, while a significant (p < 0.05, ES = 0.70-2.04, moderate to large) increase in SPR30 time in SSG1 and SSG3 was observed, HJ performance was not affected (p > 0.05, ES = 0.03-0.54, trivial to moderate) by any SSG format. These findings suggest increasing pitch size to induce greater physical demands and to use SSGs with smaller pitch size, and independently of the bout duration, to induce neuromuscular fatigue.

Beetroot juice supplementation increases concentric and eccentric muscle power output. Original investigation.

OBJECTIVES: Beetroot juice (BJ) supplementation has been reported to enhance skeletal muscle contractile function; however, it is currently unclear whether BJ supplementation elicits comparable improvements in power output during different types of skeletal muscle contractions. The purpose of the current study was to assess the effect of BJ supplementation on power output during concentric (CON) and eccentric (ECC) muscle contractions during a half-squat. DESIGN: In a randomized, double-blind placebo-controlled crossover design, eighteen adult males (age: 22.8±4.9y) completed two experimental testing sessions 2.5h following the acute ingestion of 140mL nitrate-rich BJ concentrate or a placebo. METHODS: Each experimental session comprised four sets of eight all-out half-squat repetitions with each set completed with a different moment intertia (0.025, 0.050, 0.075 and 0.100kg·m-2). RESULTS: Compared to placebo, BJ supplementation increased mean power output (MP) during the CON (ES: 0.61-1.01) and ECC (ES: 0.54-0.89; all p<0.05) movement phases to a similar extent. Moreover, comparable increases in peak power output (PP) during the CON (ES: 0.86-1.24) and ECC (ES: 0.6-1.08; all p<0.05) movement phases were observed following BJ supplementation. CONCLUSION: Acute BJ supplementation increased mean and peak lower limb power output in the concentric and eccentric movement phases of a half-squat. These findings improve understanding of the effects of BJ supplementation on skeletal muscle contractile function and might have implications for enhancing sports performance in events where muscle power output is a key performance determinant.

Effect of cycling specialization on effort and physiological responses to uphill and flat cycling at similar intensity.

Power output is considered one of the best tools to control external loads in cycling, but the relationship between a target power output and the physiological responses may suffer from the effects of road gradient, which is also affected by cyclist specialization. The objective was to determine the effects of cyclist specialization on effort perception and physiological response (heart rate and lactate concentration) while sustaining efforts at similar power output but riding on two different road gradients. Nineteen male competitive road cyclists performed two randomized trials of 10 min at 0% (velodrome) and 10 min at 6% road gradient (field uphill), at an intensity of 10% ± 3% below the individual's functional threshold power. Cadence was kept between 75 and 80 rpm in both trials and posture remained unchanged during the tests. Heart rate, speed, cadence, power output, blood lactate, and rate of perceived effort were measured for each trial. K-means cluster analyses differentiate uphill (n = 10) and flat specialists (n = 9) according to lactate responses. Flat specialists presented lower heart rate (p < 0.001 and ES = 0.2), perceived exertion (p < 0.01 and ES = 0.7), and blood lactate concentration (p < 0.001 and ES = 0.7) riding on the flat than uphill. Uphill specialists presented lower perceived exertion (p < 0.01 and ES = 0.8) and blood lactate concentration (p < 0.01 and ES = 0.5) riding uphill than on the flat. In conclusion, the combination of cyclist specialization and road gradient affects physiological and effort perception parameters in response to a similar power output demand. These factors deserve attention in training schedules and monitoring performance using power output data.

Effectiveness of a Generic vs. Specific Program Training to Prevent the Short-Term Detraining on Repeated-Sprint Ability of Youth Soccer Players.

Rodríguez-Fernández, A, Villa, JG, Sánchez-Sánchez, J, and Rodríguez-Marroyo, JA. Effectiveness of a generic vs. specific program training to prevent the short-term detraining on repeated-sprint ability of youth soccer players. J Strength Cond Res 34(8): 2128-2135, 2020-The aim of this study was to analyze the effects of 2 short-term training programs to prevent the negative effect of detraining on repeated-sprint ability (RSA) performance. The study was performed during a 2-week midseason break without official matches. Forty-five youth soccer players (17.7 ± 0.8 years, 175.4 ± 5.5 cm, and 67.2 ± 5.1 kg) were split into 3 groups during the intervention period: inactivity group (IN; N = 16), generic high-intensity training group (GG; N = 15), and specific training group (SG; N = 14). IN was instructed to avoid performing physical activity during the 2-week training intervention. However, GG and SG performed 8 training sessions. GG performed a generic aerobic interval training consisting of 4 repetitions of 4 minutes of exercise at 90-95% of maximal heart rate. SG performed a specific conditioning through small-sided games (4 vs. 4, 4 × 4-minute) and repeated sprints (6 × 30-m). Testing sessions included an RSA test and a Yo-Yo intermittent recovery test level 1 (YYIR1). Repeated-sprint ability performance only improved after the training intervention in SG (∼2%, p < 0.01, (Equation is included in full-text article.)= 0.23-0.25). Both GG and IN declined their performance in post-test (∼2%, p < 0.01, (Equation is included in full-text article.)= 0.19-0.22). No significant effect, group × time, was analyzed for YYIR1 performance. This study suggests that only specific training, based on small-sided games and repeated sprints, leads to short-term improvements on RSA performance in youth soccer players.

Acute Effects of Caffeine Supplementation on Movement Velocity in Resistance Exercise: A Systematic Review and Meta-analysis.

BACKGROUND: Several studies investigated the effects of caffeine supplementation on movement velocity in resistance exercise. However, these studies presented inconsistent findings. OBJECTIVE: This paper aimed to: (a) review the studies that explored the effects of caffeine supplementation on movement velocity in resistance exercise; and (b) pool their results using a meta-analysis. METHODS: A search for studies was performed through seven databases. Random-effects meta-analyses of standardized mean differences (SMD) were performed to analyze the data. Sub-group meta-analyses explored the effects of caffeine on different velocity variables (i.e., mean and peak velocity), different loads (i.e., low, moderate, and high loads), and upper- and lower-body exercises. RESULTS: Twelve studies met the inclusion criteria. In the main meta-analysis, in which we pooled all available studies, the SMD favored the caffeine condition (SMD = 0.62; 95% confidence interval [CI]: 0.39-0.84; p < 0.001). Sub-group analyses indicated that caffeine significantly enhances mean (SMD = 0.80; 95% CI: 0.48-1.12; p < 0.001) and peak velocity (SMD = 0.41; 95% CI: 0.08-0.75; p = 0.014), movement velocity with low loads (SMD = 0.78; 95% CI: 0.41-1.14; p < 0.001), moderate loads (SMD = 0.58; 95% CI: 0.25-0.91; p = 0.001), and high loads (SMD = 0.70; 95% CI: 0.33-1.07; p < 0.001), as well as in lower-body (SMD = 0.82; 95% CI: 0.42-1.23; p < 0.001) and upper-body exercises (SMD = 0.59; 95% CI: 0.37-0.82; p < 0.001). CONCLUSION: Acute caffeine supplementation is highly ergogenic for movement velocity in resistance exercise. Sub-group analyses indicated that caffeine ingestion is ergogenic: (a) for both mean and peak velocity; (b) for movement velocity when exercising with low, moderate and high loads, and (c) for movement velocity in both lower- and upper-body exercises. Previous meta-analyses that explored the effects of caffeine on various aspects of resistance exercise performance (i.e., muscular strength and endurance) reported trivial to moderate ergogenic effects (effect size range: 0.16-0.38). In the present meta-analysis, the pooled effect size ranged from 0.41 to 0.82. From a resistance exercise performance standpoint, this suggests that caffeine has the most pronounced performance-enhancing effects on movement velocity.

Relationship Between Repeated Sprint Ability, Aerobic Capacity, Intermittent Endurance, and Heart Rate Recovery in Youth Soccer Players.

Rodríguez-Fernández, A, Sanchez-Sanchez, J, Ramirez-Campillo, R, Nakamura, FY, Rodríguez-Marroyo, JA, and Villa-Vicente, JG. Relationship between repeated sprint ability, aerobic capacity, intermittent endurance, and heart rate recovery in youth soccer players. J Strength Cond Res 33(12): 3406-3413, 2019-To investigate the relationship between repeated sprint ability (RSA) and several aerobic and anaerobic-related soccer-performance indicators, 45 youth soccer players (age 16.8 ± 0.1 years) were classified into "high" (HAF) or "low" aerobic fitness (LAF) (VO2max ≥ or <60 ml·kg·min, respectively) and completed an RSA test measuring best (RSAbest), mean (RSAmean), total sprint time (RSAtotal), and percent sprint decrement (Sdec). A laboratory VO2max test (LabTest) together with anaerobic threshold (VT) and peak speed was measured (vLabTest). In addition, a 20-m multistage shuttle run test (MSRT) and a soccer-specific test (TIVRE-Soccer test-TST) were completed. Heart rate (HR) and HR recovery (HRR) were measured during all tests. High aerobic fitness presented greater (p ≤ 0.05) performance in LabTest, MSRT and TST, at maximal effort, at VT, as well as faster HRR. RSA was similar between HAF and LAF. Contrary to HAF, LAF showed negative correlation between vLabTest with RSAmean (r = -0.6, p = 0.000) and Sdec (r = -0.4, p = 0.044). Also, LAF showed negative correlation between TST end speed (vTST) and RSAmean (r = -0.5, p = 0.005) and Sdec (r = -0.5, p = 0.003). In LAF, RSA was strongly correlated with locomotor factors (e.g., vTST; VT) in both laboratory and field tests. Athletes with high total HRR (>12.5%) in TST presented better (p ≤ 0.05) Sdec in the RSA test. The multiple regression revealed that the LAF vLabTest explained 44.9, 40.0, and 13.5% of the variance in RSAbest, RSAmean, and Sdec, respectively. Practitioners may consider these findings to optimize youth athletes' assessment and preparation processes.

Effects of Caffeine Supplementation on Power Performance in a Flywheel Device: A Randomised, Double-Blind Cross-Over Study.

Despite the demonstrated evidence of the importance of eccentric contractions in sports performance, no research has evaluated the ergogenic effects of caffeine on this type of contraction means during flywheel exercises. Therefore, the aims of the present study were to compare the power outcomes, using different inertial loads, between caffeine and placebo conditions. Twenty-four young, healthy, and active men (age: 22.5 ± 4.8 years) took part in the study. A crossed, randomised double-blind design was used to analyse the effects of caffeine on lower limb power outcomes during a flywheel half-squat exercise. Participants completed four sets of eight all-out repetitions with a fixed three-minutes rest interval, and each set was performed using different inertial loads (i.e., 0.025, 0.050, 0.075 and 0.100 kg·m-2). Both the mean power (MP) and peak power (PP) in concentric (CON) and eccentric (ECC) movement phases at each inertial load were recorded after participants were administered either a caffeine supplement (6 mg·kg-1) or placebo (sucrose). Participants receiving a caffeine supplementation demonstrated improvements versus the placebo in total MP (MPtotal), as well as MP in CON phase (MPcon) and in ECC phase (MPecc) at each inertial load (22.68 to 26.53%; p < 0.01, effect size (ES) = 0.89⁻1.40). In addition, greater improvements with caffeine ingestion were obtained with respect to the placebo condition (18.79 to 24.98%; p < 0.01, ES = 1.03⁻1.40) in total PP (PPtotal), as well as PP in CON phase (PPcon) and in ECC phase (PPecc) at each inertial load. Thus, the supplementation of 6 mg·kg-1 caffeine may be considered to maximise on-field physical performance in those sports characterised by high demands of resistance.

Effects of Repeated Sprints With Changes of Direction on Youth Soccer Player's Performance: Impact of Initial Fitness Level.

Sanchez-Sanchez, J, Ramirez-Campillo, R, Petisco, C, Gonzalo-Skok, O, Rodriguez-Fernandez, A, Miñano, J, and Nakamura, FY. Effects of repeated sprints with changes of direction on youth soccer player's performance: impact of initial fitness level. J Strength Cond Res 33(10): 2753-2759, 2019-The aim of this study was to assess the effect of an 8-week repeated sprint with change of direction (RS-COD) training program on RS, intermittent endurance, and change of direction performance in youth soccer players with different aerobic fitness levels. Athletes were randomly assigned into a soccer-only (n = 9; age, 14.9 ± 0.4 years) and soccer plus RS-COD training programs for players with high (n = 10; age, 14.4 ± 0.5 years) and low (n = 10; age, 14.4 ± 0.5 years) aerobic fitness. Repeated sprint with change of direction was completed 2 days per week, involving 3 sets of ten 18-m sprints with 2 changes of direction of 90°. The soccer-only group achieved greater improvements in intermittent endurance (effect size [ES] = 0.61) and sprint decrement during RS ability test (ES = 0.77) compared with the RS-COD groups (ES = 0.19-0.24; ES = -0.27 to 0.02; respectively). Repeated sprint with change of direction training improved RS (ES = 0.16-0.38) and change of direction (ES = 0.48) performance in high but not in low-fitness players (ES = 0.03-0.13; ES = 0.16; respectively). Moreover, improvements in RS and change of direction were (possibly) greater in high compared with low fitness and soccer-only trained players (possibly to very likely). In conclusion, although RS-COD training may positively affect RS and change of direction performance, its effects may vary according to the initial aerobic fitness of youth soccer players, with trivial effect on intermittent endurance in high-aerobic fitness players and possible beneficial effect on low-aerobic fitness players.

Assessment of the external load of amateur soccer players during four consecutive training microcycles in relation to the external load during the official match

Aim: The aim of this study was to assess the external load of amateur male players during 4 consecutive training microcycles (M) at the beginning of the in-season according to the training session in absolute external load demands and in relation to the competition demands. Methods: Regional-level players (n = 10; age, 20.8 ± 1.7 years; height, 175.5 ± 3.8 cm; body mass, 69.7 ± 2.9 kg; soccer experience, 13.2 ± 2.5 years) were monitored using GPS devices during training sessions and matches. The external load variables measured were: duration (min); total distance covered (TD); distance covered at high-speed (HID, 14.4-19.8 km/h); distance covered at sprinting (SPD; >19.8 km/h); and distance covered in high intensity acceleration (ACD; >2.5 m/s2) and deceleration (DECD; <-2.5 m/s2). Results: The results indicated that the external load variables (time, HID, SPD, ACD, and DECD) were similar between the four microcycles. Greater (p<0.01) time, TD, HID and SPD were observed in match day (MD)-2 compared to MD+1, MD-3, and MD-1. Aside from training duration, all external loads variables (TD, HID, SPD, ACD, and DECD) were lower during training sessions compared to official matches (p<0.05). Conclusion: Amateur soccer players present relative stable external training loads across competitive microcycles, with the peak load observed two days before the official match. Besides this, the match constitutes the highest load during a typical competitive microcycle in this cohort of players.(AU)