Abstract
OBJECTIVE: The optimum relationship combination of variable to constant resistance within variable resistance training (VRT) for enhancing lower-limb strength and power remains unclear. This study aimed to investigate how different ratios of variable to constant resistance in VRT affect lower-limb strength and power. METHODS: Forty-five male college students (age: 21.65 ± 2.20 years; height: 179.65 ± 4.98 cm; body mass: 77.21 ± 6.77 kg; resistance training experience: 3.00 ± 0.96 years) were randomly assigned to three groups: 20 % VRT (n = 15), 35 % VRT (n = 15), and constant resistance training (CRT, n = 15). All groups trained squats twice weekly for 6 weeks at 80 % 1RM total load (20 % VRT: 20 % variable resistance combined 80 % constant resistance; 35 % VRT: 35 % variable resistance combined 65 % constant resistance; CRT: 100 % constant resistance). Pre- and post-experiment tests included squat 1RM, countermovement jump (CMJ), squat jump (SJ), standing broad jump (SBJ), 20-m sprint, and rectus femoris cross-sectional area (RFCSA). A mixed-design ANOVA (group × time) was used for data analysis. RESULTS: The 20 % VRT group surpassed CRT in maximal strength cross-sectionally (F = 3.565, p = 0.037) but not longitudinally (p = 0.079). All groups improved strength over time (p < 0.001; Cohen's d = 0.87-0.94). A significant interaction (F = 3.407, p = 0.043) indicated SJ improvement for 35 % VRT vs. CRT (p < 0.05, Cohen's d = 0.43), with no CMJ, SBJ, sprint, or RFCSA differences (p > 0.05). CONCLUSION: VRT and CRT yield equivalent long-term strength gains. Different combinations of variable to constant resistance ratios in VRT (20 % and 35 %) led to distinct task-specific adaptations in lower-limb performance. Practitioners should prioritize 35 % VRT for static explosive tasks, use 20 % VRT as a supplementary strength tool.