Independent and combined effects of low-load variable resistance and blood flow restriction on post-activation performance enhancement in countermovement jump

Low-load blood flow restriction (BFR) induces post-activation performance enhancement (PAPE), but its constant-resistance nature involves a terminal deceleration phase that attenuates terminal mechanical tension. Combining BFR with variable resistance (VR) may overcome this mechanical deficit. Utilizing a randomized crossover design, 17 strength-trained males completed four protocols (4 × 15 back squats): control (CON), VR (27–33% 1RM), BFR (30% 1RM, 80% arterial occlusion pressure), and BFR + VR. Countermovement jump (CMJ) kinetics—jump height (JH), relative peak power (RPP), net impulse (NI), and peak rate of force development (PRFD)—were assessed at baseline and up to 15 min post-intervention. CON yielded no significant changes, whereas VR elicited selective, smaller-magnitude enhancements; BFR induced significant PAPE, peaking at 12 min before decaying. The BFR + VR protocol induced an acute performance decrement at 0 min (JH: -8.1% ± 5.4%; p < 0.001), followed by a delayed, high-magnitude potentiation. By 15 min, BFR + VR elicited its greatest observed response across all metrics (JH: +18.1% ± 7.6%; PRFD: +49.3% ± 22.4%; all p ≤ 0.001), significantly outperforming CON and VR, while demonstrating superior JH ( p = 0.041, d = 0.67, 95% CI: [0.14, 1.20]) and PRFD ( p = 0.047, d = 0.69, 95% CI: [0.16, 1.22]) compared to isolated BFR. Both protocols require a minimum 6-minute recovery. BFR-induced potentiation declines after 12 min, whereas BFR + VR maintains an upward trajectory at 15 min without decay, indicating the true peak may lie beyond the observed window.