Comparison of Variable Resistance and Free Weight Training on Long-Term and Acute Effects on Different Assessments of Strength: A Systematic Review and Meta-Analysis

Abstract

Li, J, Chen, Z, Xu, K, Wang, Y, and Gong, M. Comparison of variable resistance and free weight training on long-term and acute effects on different assessments of strength: a systematic review and meta-analysis. J Strength Cond Res 40(2): e211-e223, 2026-Variable resistance training (VRT) addresses biomechanical disadvantages of free weight training (FWT), but its long-term and acute effects on strength remain underexplored. This study aimed to compare the effects of VRT and FWT on the following variables-maximal strength, velocity, power output, and jump distance-under both long-term and acute interventions. The study used cluster analysis to define variable resistance load proportion (VRLP) groups. Pairwise meta-analysis assessed long-term outcomes, subgroup analyses by VRLP, VRT equipment (elastic bands or chains), and number of VRT exercises (single or multiple). Acute interventions were evaluated using network meta-analysis across VRLP and FWT groups. Effect sizes were reported as standardized mean differences (SMD). For long-term effects, VRT outperformed FWT in maximal strength (repetition maximum or force output) and jump distance (vertical or horizontal) (0.28 ≤ SMD ≤ 0.37). Specifically, chain-based loading and VRLP ≤20% showed advantages across both outcomes (0.39 ≤ SMD ≤ 0.51). Multiple-exercise VRT improved maximal strength (SMD = 0.27), whereas single-exercise VRT improved jump distance (SMD = 0.46). For acute effects, VRLP >20% showed superior maximal strength (force output) (0.46 ≤ SMD ≤ 0.79), VRLP >37% resulted in lower maximal velocity (movement velocity) and power output (SMD ≤ -1.31) compared with FWT. Thus, long-term VRT surpasses FWT in maximal strength and jump distance, with chain-based or VRLP ≤20% of VRT optimal; multiple exercises benefit maximal strength, and single exercise improves maximal jump distance. Acutely, VRLP of 21-37% VRT results in greater mechanical output in a variety of exercises.

Keywords: accommodating resistance training; chain resistance; constant resistance training; elastic resistance; exercise prescription; strength and conditioning.