Subjective Monitoring in Under-20 Soccer Athletes: Affective, Load, Monotony, and Sleep Variations throughout a Competitive Cycle.

Introduction: The physical and mental demands of competitive soccer, combined with a high density of matches and training sessions, impose substantial psychophysiological stress on athletes. In this context, subjective variables, such as affective responses, perceived exertion, and sleep, emerge as important indicators, offering additional insights into players' readiness and recovery. However, few studies have examined these variables in an integrated manner over extended periods of preparation and competition. Objective: This study aimed to investigate the effects of soccer training sessions and matches on affective responses (valence and arousal), perceived exertion, and sleep duration in under-20 soccer athletes. Additionally, the objective of this study was to assess correlations between affective responses and traditional internal load variables (RPE), monotony, strain, and self-reported sleep duration. Methods: This observational study was conducted with 21 under-20 athletes from a Brazilian elite soccer team over 11 weeks encompassing training sessions, friendly matches, and official competition. Affective responses were assessed before and 30 minutes after each session using the Feeling Scale (FS) and the Felt Arousal Scale (FAS). Perceived exertion (RPE), sleep duration, monotony, and strain were recorded daily. Two-way ANOVA was applied for FS and FAS, while one-way ANOVA was used for weekly training load, sleep, monotony, and strain. Mann-Whitney tests (match vs. training) were also performed. Pearson's correlation coefficients were calculated between variables. The significance level was set at p < 0.05. Results: There were significant main effects of week and moment (pre/post) for both FS and FAS, with a notable decrease in affective responses after sessions (p < 0.0001). Sleep duration progressively increased from the seventh week onward (p < 0.05), whereas training load, monotony, and strain fluctuated across the weeks, with significant declines toward the end of the cycle. Significant differences between matches and training sessions were found for training load (p = 0.0333) and sleep duration (p < 0.0001), but not for affective scales. On an individual level, 71% of athletes showed a reduction in affective responses post-session. Correlations between affective and the other variables were trivial to small (ranging from r = 0.11 to r = 0.24), with slightly more consistent associations for sleep and RPE. Conclusion: There was a significant reduction in FS over the weeks. Fluctuations in FS were observed across weeks in line with accumulated load and competition demands. Seventy-one percent of athletes showed a decrease in FS post-activity. The monotony and strain showed a declining trend over the competitive cycle, particularly in the latter weeks, indicating a reduction in training variability and cumulative load. These reductions coincided with an increase in self-reported sleep duration, suggesting a favorable shift in the balance between training stress and recovery. Finally, FS displayed weak correlations with perceived exertion, monotony, strain, and sleep duration.