The aims of this study were to analyse the physical responses of professional soccer players during training considering the contextual factors of match location, season period, and quality of the opposition; and to establish prediction models of physical responses during training sessions. Training data was obtained from 30 professional soccer players from Spanish La Liga using global positioning technology (N=1365 performances). A decreased workload was showed during training weeks prior to home matches, showing large effects in power events, equivalent distance, total distance, walk distance and low-speed running distance. Also, the quality of the opposition also affected the training workload (p<0.05). All regression-models showed moderate effects, with an adjusted R2 of 0.37 for metabolic-work, 0.34 for total distance covered, 0.25 for high-speed running distance (18–21 km·h−1), 0.29 for very high-speed running distance (21–24 km·h−1), 0.22 for sprint running distance (>24 km·h−1) and 0.34 for equivalent distance. The main finding of this study was the great association of match location, season period and quality of opposition on the workload performed by players in the training week before the match; and the development of workload prediction-models considering these contextual factors, thus proposing a new and innovative approach to quantify the workload in soccer.

This study aimed to analyze perceptual, metabolic and mechanical responses to sprint training sessions. 9 male high-level sprinters performed 40 m running sprints up to a loss of 3% in speed, with 4 min rests between sets. Perceptual (rating of perceived exertion, RPE), mechanical (speed and countermovement jump height loss) and metabolic (blood lactate and ammonia) parameters were measured pre-exercise and after each sprint was performed. Relationships between the variables were calculated with a 90% confidence interval. Jump height loss showed almost perfect relationships with both blood lactate (r=0.96 (0.95 to 0.97)) and ammonia (r=0.95 (0.94 to 0.95)), whereas speed loss, number of sprints performed and RPE values showed large-very large relationships with blood lactate and ammonia. Furthermore, an almost perfect curvilinear relationship was observed between lactate and ammonia concentrations (R(2)=0.96 (0.95 to 0.97)). These results suggest that countermovement jump (CMJ) height can be used to quantify the fatigue induced during a typical sprint training session, and may prove a useful tool to facilitate individualized load monitoring. The results indicate that the CMJ is a better monitor of metabolic fatigue than traditional measures.

This study analyzed the acute metabolic and mechanical responses to a specific repeated sprint ability (RSA) test. Eighteen male professional soccer players from a team of the First Division of Spanish National League participated. A 12 × 30-m RSA test with 30-second recovery together with countermovement jump test (CMJ) pre a post RSA test was performed. Mechanical responses (i.e., height performance in CMJ and speed loss) and metabolic responses (i.e., blood lactate and ammonia concentrations) were measured before and after exercise. A related sample t-test was used to analyze CMJ height pre-post changes as well as to compare pre- and post-exercise lactate and ammonia levels. Countermovement jump height loss pre-post session (8%) was significant, and fatigue, measured as CMJ height loss, was strongly correlated to lactate (r = 0.97; p < 0.001) and ammonia (r = 0.92; p < 0.001) for all players. The relationships between the variables studied were determined by calculating the Pearson correlation coefficients. The metabolic stress developed during the effort can be estimated by controlling CMJ because of the high correlation between CMJ and blood lactate and ammonia concentrations. The high correlations found between mechanical (speed and CMJ height losses) and metabolic (lactate and ammonia) measures of fatigue highlight the utility and validity of using CMJ to monitor training load and quantify objectively neuromuscular fatigue during RSA.

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