Effects of Complex and Contrast Training on Lower Limb Explosive Power and Eccentric Strength in Elite Male Track and Field Athletes: A 24-Week Randomized Trial

ABSTRACT: Xu, Z, Lin, Y, Zhang, F, Li, Q, Yu, L, Lin, M, Ning, F, and Wang, X. Effects of complex and contrast training on lower limb explosive power and eccentric strength in elite male track and field athletes: A 24-week randomized trial. J Strength Cond Res XX(X): 000-000, 2026-This 24-week randomized controlled trial compared the effects of complex training (postactivation potentiation) and contrast training (postactivation performance enhancement) on lower-limb explosive power (jump height, push-off power) and eccentric strength (drop height, countermovement impulse) in track and field athletes, while assessing arm swing's role in kinetic chain coordination. Forty-five national-level track and field athletes were randomized into complex training, contrast training, or control groups. Kinetic data were collected using a 3-dimensional force plate. Repeated-measures ANOVA and multivariate regression (ΔR2) analyzed intervention effects under arm-swing and non-arm-swing conditions, with cross-group comparisons. Cross-group analyses showed complex training significantly outperformed contrast training and control in jump height with arm swing (+30.9%, 0.55-0.72 m, P < 0.001 vs. +17.1%, 0.58-0.68 m, P = 0.012 vs. +7.7%, 0.52-0.56 m, P = 0.231) and drop height (+30.4%, 0.46-0.60 m, P < 0.001 vs. +15.2%, 0.46-0.53 m, P = 0.031 vs. +5.2%, 0.46-0.48 m, P = 0.672). Contrast training excelled in reducing push-off time without arm swing (-6.1%, 0.214-0.201 seconds, P = 0.002 vs. +1.2%, P = 0.721 vs. +0.8%, P = 0.821) and increasing push-off power (+17.1%, 122.23-129.02 W·kg-1, P = 0.009 vs. +9.8%, P = 0.041 vs. +2.3%, P = 0.762). Arm swing enhanced eccentric-concentric efficiency, with complex training showing stronger correlations (push-off power vs. jump height: r = 0.527, P < 0.001). Eccentric strength explained 43.1% of jump height variance (R2 = 0.431, P < 0.001). Complex training enhances elastic energy storage, whereas contrast training improves neural coordination. The results support tailored training based on eccentric strength and sport-specific needs.