Acute Effect of Alternative Complex-Contrast Training Set Strategies on Vertical Jump Propulsive Impulse and Rate of Force Development

Complex-contrast training (CCT) is an advanced training method that aims to augment explosive force application through post-activation performance enhancement (PAPE). However, the intra-contrast rest periods (ICRP) required to observe PAPE are typically 5-12 minutes, making CCT impractical for most training scenarios. This study, therefore, aimed to assess whether combining CCT sets with rest redistribution (RR) strategies could reduce the total contrast rest period (TCRP) required to observe PAPE in vertical jump metrics. 15 male subjects completed 10 experimental interventions across 5 data collection sessions in a counterbalanced cross-sectional design. Interventions consisted of 2 vertical jump variations (countermovement jump (CMJ) and squat jump (SJ)) and 5 TCRPs (TCRP; 60, 120, 180, 240, 300 s), partitioned as 0, 60, 120, 180, 240 s ICRP, respectively, and 60 s of RR. Within interventions, participants performed a control condition consisting of 1 set of vertical jumps (BASELINE), the assigned ICRP, then a second set of jumps (PRE-BS). This was followed by an experimental condition consisting of 3RM back squats with 30 s between repetitions, then the ICRP, and a final set of jumps (POST-BS). Vertical jump propulsive impulse (JPROP) and related force-time components were assessed. A 5x2x2 (TCRP*CONDITION*TIME) repeated measures ANOVA assessed differences in force-time variables. Results showed no significant interaction of TCRP*CONDITION*TIME for JPROP, indicating that, regardless of intervention, neither CMJ nor SJ JPROP was enhanced. However, RR led to significant increases in both peak and average CMJ rate of force development (RFD) and reduced propulsion time (tPROP) after TCRP180, TCRP240, and TCRP300, demonstrating a more explosive, but not higher, jump. For SJ, no meaningful changes in RFD or tPROP were observed. Thus, RR may preserve JPROP while augmenting explosive force application via enhanced eccentric-concentric coupling and stretch-shortening cycle efficiency, but PAPE remains insufficient to increase jump height in recreationally strong populations. Practically, RR may reduce the time required within CCT sets to observe PAPE through enhanced RFD. This combined approach may also be an effective tool for increasing training density by maintaining explosive capacity during power phases without impairing performance. However, longer rest may still be necessary when maximising impulse is the primary goal.