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Purpose:  This study aims to investigate the effects of rest intervals, sprint distance, and number of repetitions on performance variables, physiological responses, and energy system contributions in repeated-sprint protocols when total distance variable was the controlled (300 m).  Method:  Sixteen male soccer players participated in this study. The four protocols, each totaling a distance of 300 m, consisted of the combination of 15 and 30 m sprints with 30 s rest intervals (15meters30sec and 30meters30sec, respectively) and 1:5 work–rest ratios (15meters12sec and 30meters22sec, respectively). Aerobic, glycolytic, and phosphagen energy systems’ contributions were calculated from the oxygen consumption (VO2) during the exercise, net lactate production, and the recovery VO2 kinetics using mono-exponential models. Repeated measures ANOVA with the Bonferroni correction was applied to examine the hypothesized differences.  Results:  The findings indicated that total sprint duration (F3:45=281.14; p&lt;0.001), percentage of performance decline (F3:45=16.58; p&lt;0.001), delta lactate (F3:45=39.72, p&lt;0.001), rating of perceived exertion (F3:45=28.64; p&lt;0.001), energy demand (F3:45=101.6; p&lt;0.001), VO2 during the rest intervals (F3:45=42.72; p&lt;0.001), and the absolute contribution of glycolytic (F3:45=119.6; p&lt;0.001) and phosphagen energy systems (F3:45=72.9; p&lt;0.001) were lowest in the 15meters30sec compared to other protocols. However, the relative contribution of aerobic system was greatest in the 15meters30sec compared to other protocols (F3:45=28.1, p&lt;0.001). Both absolute (F3:45=119.6; p&lt;0.001) and relative contribution of glycolytic system (F3:45=88.5, p&lt;0.001) were greatest in the 30meters22sec compared to other protocols.  Conclusion:  This study showed that increasing sprint distance when rest interval is equal and decreasing rest interval when sprint distance is equal can increase the glycolytic system contribution.

The Contribution of Energy Systems in Repeated-Sprint Protocols: The Effect of Distance, Rest, and Repetition