Purpose: The objective of this study was to investigate the impact of a 6-week program involving various forms of running-based interval interventions on the physiological and performance adaptations of male soccer players during preseason. Methods: A total of 40 young trained collegiate soccer players (21 [1.3] y) were randomly assigned to 4 groups: traditional sprint interval training (SIT, 20-s trials), small-sided games, repeated-sprint training (RST, 5-s trials), and an active control group, each of 10 members. Physiological variables, including maximum oxygen uptake, first and second ventilatory thresholds, and peak and average power output, were assessed before and after the 6-week intervention. In addition, performance outcomes including countermovement vertical jump, 20-m sprint, L-run change-of-direction speed, and the Yo-Yo Intermittent Recovery Test 1 (Yo-Yo IR1) were also measured. Results: The SIT, small-sided games, and RST groups demonstrated significant (P < .05) improvements in the countermovement vertical jump (effect size [ES] = 0.89, 0.98, 1.01), 20-m sprint (ES = -0.86, -0.53, -1.22), L-run change-of-direction speed (ES = -1.65, -1.79, -2.55), Yo-Yo IR1 (ES = 1.79, 1.09, 2.15), maximum oxygen uptake (ES = 1.22, 0.49, 1.29), first ventilatory threshold (ES = 1.38, 0.63, 1.44), second ventilatory threshold (ES = 0.96, 0.56, 0.97), peak power output (ES = 0.94, 0.89, 1.21), and average power output (ES = 1.05, 0.89, 0.91) after the training intervention. When comparing the magnitude of changes (ie, %change) among the training groups, the SIT and RST groups showed more enhancements compared with the small-sided games in the Yo-Yo IR1 (15.9% and 20.8% vs 11.1%, P = .005, .001), maximum oxygen uptake (5.9% and 6.4% vs 3.5%, P = .001), first ventilatory threshold (6.3% and 6.9% vs 4.2%, P = .001), and second ventilatory threshold (4.3% and 4.4% vs 3.1%, P = .007, .042). In addition, the RST group demonstrated more training gains compared with the SIT in the 20-m sprint (-7.2% vs -4.2%, P = .001), Yo-Yo IR1 (20.8% vs 15.9%, P = .005), and peak power output (10.2% vs 8.0%, P = .008) after the training intervention. Conclusion: All training interventions led to improvements in physiological and performance adaptations among young soccer players. The RST group achieved the greatest gains compared with the other protocols. These findings highlight RST as a particularly effective strategy for enhancing soccer player performance.
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