Cluster-set rest vs. traditional during repeated sprint training: effects on creatine phosphokinase activity, sprint abilities and 100-m sprint performance

Background This study examined the effects of cluster-set rest and traditional rest interval configurations during repeated sprint training on creatine phosphokinase enzyme (CPK) activity, sprint abilities, and 100-m sprint performance. Methods The study was carried out using a nonrandomized experimental design involving twenty well-trained male sprinters. Participants were assigned to two equally sized groups: the Cluster Set Rest Group (CSRG) and the Traditional Rest Group (TRG). The eight-week training intervention included 24 sessions, with three weekly training days. All variables were assessed pre- and post-intervention. CPK activity was assessed through biochemical analysis, while sprint abilities were evaluated using the 0–40 m sprint and repeated sprint ability 6 × 30-m (RSAT 6 × 30) tests. The 100-m sprint time (100 m SP time) was measured in accordance with the regulations set forth by world athletics. Results Significant group × time interactions were identified using a 2 × 2 mixed-factorial Analysis of Variance (ANOVA) for CPK activity ( p < 0.001), RSAT 6 × 30 parameters (peak sprint speed: p = 0.003; mean sprint speed: p = 0.010; fatigue index: p = 0.009), and 100-m SP time ( p = 0.031), with the CSRG exhibiting significantly greater improvements than the TRG. CPK activity increased from 214.4 ± 40.45 U/L to 358.2 ± 18.74 U/L in the CSRG compared with 224.9 ± 29.03 U/L to 302.6 ± 13.84 U/L in the TRG. Likewise, 100-m SP time improved from 12.08 ± 0.25 s to 11.80 ± 0.16 s in the CSRG, whereas the TRG improved from 12.12 ± 0.24 s to 11.96 ± 0.25 s. No significant group × time interactions were detected during the acceleration phases (0–10 m, 0–20 m, and 0–30 m) of the 0–40 m sprint test ( p = 0.160, 0.235, and 0.265, respectively). In contrast, a significant interaction effect was identified during the flying sprint phase (20–40 m; p = 0.008). Discussion These findings highlight the efficacy of cluster-set rest (CSR) protocols in enhancing energy-system function and sprint performance, providing practical implications for the design of high-intensity sprint-training programs. These results may assist coaches and athletes in designing sprint-training programs that optimize recovery distribution and performance outcomes.