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Hertzog, M, Rumpf, MC, and Hader, K. Resistance training status and effectiveness of low-frequency resistance training on upper-body strength and power in highly trained soccer players. J Strength Cond Res 34(4): 1032-1039, 2020-Soccer is classified as a contact/collision sport with many player-to-player duels. Winning these duels, shielding the ball or fending off an opponent requires upper-body strength and power. Therefore, this study aimed (a) to examine the time-related effect of an upper-body resistance training (RT) on maximal strength and power changes in highly trained soccer players and (b) to investigate if the RT status influences these changes throughout a competitive season. Twenty-eight soccer players participated in this study and were divided into an untrained group (UG) and a trained group (TG), according to their RT status. Both groups performed the same upper-body RT once a week, over 30 weeks. Maximal strength (1 repetition maximum [1RM]) and maximal power (MP) were assessed before, during, and after the competitive season. Both groups significantly improved 1RM and MP over the entire competitive season, with a moderate (TG, 13%) to very large (UG, 21%) magnitude in 1RM and with a small (TG, 8%) to moderate (UG, 13%) magnitude in MP. After the initial 10 weeks of RT, UG presented significant and slightly (1RM) to moderately (MP) greater improvements than TG. For all other time intervals, the between-groups' changes in 1RM were rated as similar. For the last 20 weeks of the RT, the change in MP was significantly lower for UG compared with TG. One upper-body RT session per week will provide sufficient stimulus to enable an almost certain improvement in strength and power throughout a competitive season for all players disregarding their initial RT status.

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BACKGROUND: Monitoring athletes' external load during a soccer match may be useful to predict post-match acute and residual fatigue. This estimation would allow individual adjustments to training programs to minimize injury risk, improve well-being, and restore players' physical performance and inform the recovery process. METHODS: Using a systematic review and meta-analysis of the literature, the aim is to determine which monitoring variables would be the strongest predictors of acute (immediately) and residual (up to 72 h) fatigue states in soccer. PubMed, SPORTDiscus, and Web of Science databases were searched (until September 2018). Studies concurrently examining soccer match-related external load metrics and subjective and/or objective measures were selected to determine pooled correlations ([Formula: see text]) with confidence intervals (CI). The quality and strength of the findings of each study were evaluated to identify overall levels of evidence. RESULTS: Eleven studies were included (n = 165 athletes). Acute ([Formula: see text] = 0.67; 95% CI = [0.40, 0.94]) and residual (24 h post-match, [Formula: see text] = 0.54; 95% CI = [0.35, 0.65]) changes in muscle damage markers and countermovement jump peak power output (CMJPPO) were, with moderate to strong evidence, largely correlated with running distance above 5.5 m s-1. No other external load metric was largely correlated with both biochemical and neuromuscular markers. For every 100-m run above 5.5 m·s-1, CK activity measured 24 h post-match increased by 30% and CMJPPO decreased by 0.5%. Conversely, the total distance covered did not present any evidence of a clear relationship with any fatigue-related marker at any time-point. CONCLUSIONS: Running distance above 5.5 m·s-1 represents the most sensitive monitoring variable characterizing biochemical and neuromuscular responses, at least when assessed during the initial 24 h (not at 48 h/72 h) post-match recovery period. In addition, total distance covered is not sensitive enough to inform decision-making during the fatigue monitoring process.

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The purpose of this longitudinal study was to investigate whether recruitment status influences neuromuscular and endurance performances in academy soccer players over a 2-year training period (from Under-16 to Under-18). Thirty-seven male soccer players from an elite academy were selected and divided in two cohorts according to their recruitment status: Early Recruitment group (ER; n = 16), training and competing for the academy since Under-14 and Under-15 age groups, and; Late Recruitment group (LR; n = 21) included in the academy training process at Under-16. Squat (SJ) and countermovement jump with (CMJwA) and without arms swing (CMJ), 10-m sprint time, and Vam-Eval test (MAV) were performed in three successive occasions always pre-season (Under-16, Under-17 and Under-18 age groups, T1, T2, and T3 respectively). A two-way (recruitment status × time) analysis of variance with repeated measurements was performed as well as the magnitude of difference using both effect size and magnitude-based inferences. There was no difference between ER and LR for MAV, 10 m-sprint, and SJ from T1 to T3. However, LR players presented non-significant small and possibly greater improvement in CMJ (ES = 0.4) and CMJwA (ES = 0.4) than ER players at T2. These data indicate that early recruitment is not likely to result in greater physical performance improvement at the age of 18.

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BACKGROUND: The purpose of the present study was to investigate the technical and physical performance parameters that distinguish between teams winning and losing matches in the 2014 FIFA World Cup Brazil. METHODS: Data were derived from the FIFA website and from live-statistics provided during each game of the world cup. Twelve physical (such as total distance covered in meters (TD), TD in distinct locomotor categories: low-intensity running (LIR; <11 km/h), moderate-intensity running (MIR; 11 to 14 km/h) and high-intensity-running (HIR; >14 km/h)) and 21 technical parameters (total passes, short-, medium- and long-distance passes, total pass completion rate, dangerous attacks, attacking attempts, delivery in penalty area, ball possession, goals, goals from set-pieces, goals per shot on goal, defending saves, shots, shots on goal, shot accuracy, set-pieces, crosses, corners, clearances, yellow cards) were analyzed. Forty-two games in which a winner and consequently a loser were presented after 90 minutes of game time were investigated with independent t-tests. A binary-logistic regression was utilized to investigate whether the significant variables predicted success of the winning teams. RESULTS: The winning teams scored significantly (P<0.05) greater amount of goals, goals per set-pieces, goals per shots on goals, shots on goal and shot accuracy and received significantly lower yellow cards. The binary-logistic regression utilized showed that shot accuracy was the best predictor for success. The physical parameters did not differ between teams winning and losing a match. CONCLUSIONS: Technical performance related to goal scoring parameters play a decisive role in World Cup games. Furthermore, scoring efficacy from open-play as well as from set-pieces are crucial to win matches in a World Cup tournament. At this level, physical performance was not the factor to discriminate between winners and losers.

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This study analyzed training loads of youth soccer players and examined the influence of match-related contextual variables in internal training load and fatigue. A secondary aim was to investigate the variability of these parameters throughout the season. Thirteen highly trained under-19 players (18.6 ± 0.5 years) were followed during one season. Training load (daily) and fatigue scores (weekly) were assessed using rate of perceived exertion and a short questionnaire, respectively. Higher weekly training loads were reported after a defeat or draw compared to a win (2,342 ± 987 and 2,395 ± 613 vs. 1,877 ± 392 AU; p ≤ 0.05; d = 0.30-0.45). Weekly training loads were higher after playing an away match than after a home match (2,493 ± 821 vs. 2,153 ± 577 AU; p ≤ 0.05; d = 0.23). Within training sessions, the coefficients of variation for internal training load ranged from 5 to 72%. Throughout the season, the coefficients of variation for weekly training loads and fatigue scores ranged from 29 to 49% and 18 to 44%, respectively. Weekly training load decreased as the season progressed (p < 0.001); no changes were detected for the fatigue score. In conclusion, the large variation in internal training load within a session and its sensitivity to initial and subsequent match conditions underline the need for a more individualized approach. These findings and the stability of the fatigue scores throughout the season may indicate that highly trained players modulate their pace during training.

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According to the spring mass model, leg stiffness (characterized by the measure of kleg) behavior is theoretically dependent on lower limb joint and trunk stiffness. Yet, the influence of the trunk as a possible regulator of kleg is unknown. This study investigated the influence of abdominal training on kleg during hopping tasks. Fourteen young male (age 18.5 ± 0.5 years, height 176.4 ± 4.3 cm, weight 69.9 ± 5.5 kg) soccer players (national level) participated in the study. Two groups (bracing B group, n = 7 vs. hollowing transversus abdominis [TrA] H group, n = 7) with identical training load followed an 8-week training program for abdominal strengthening. Contact time, flight time, jump height, and kleg were measured with an OptoJump system during a standardized hopping task (2.2 Hz) before and after the training program. Results for each group showed that only the H group increased kleg after the intervention (+15.7%) compared with the B group (+5.9%). This difference was explained by a 6.5% decrease in contact time in H group (-2.4% in B) with increased flight time (+8.8% in H vs. +2% in B). A large increase was found for jump height in H (+16.9%) compared with B group (+4.4%). This study showed that TrA strengthening improves leg stiffness in hopping tasks. Our findings suggest the potential role of abdominal muscles in controlling "lumbopelvic" stiffness as a part of the spring according to the spring mass model, and thus influencing kleg by reduced ground contact phase.

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