Joint-Level Analysis of the Barbell Back Squat During Chain and Elastic Variable Resistance Use

Alves, AV, Leicht, AS, Deakin, GB, Doma, K, Singh, U, and Brice, SM. Joint-level analysis of the barbell back squat during chain and elastic variable resistance use. J Strength Cond Res 40(5): 511-518, 2026-This study identifies the kinetic and kinematic differences between elastic (EVR) and chain variable resistance (CVR), and free-weight resistance (FW) use during the barbell back squat. Fifteen men (1RM = 124.2 ± 30.4 kg) completed 5 sessions during 4 weeks: 1-repetition maximum (1RM) testing session; variable resistance (VR) familiarization session; and 3 testing sessions. Peak ground reaction force (GRF) and rate of force development (RFD), along with sagittal plane joint range of motion (ROM), angular velocity, moments, and power, were examined. Peak GRF was significantly greater for FW than for both VR conditions (p < 0.05). Concentric RFD was significantly greater for CVR than for FW (p < 0.05). No differences in joint ROM were observed across the 3 conditions (p > 0.05). In most cases, both VR conditions elicited faster lower limb angular velocities than FW during the concentric and eccentric phases (p < 0.05). Despite external resistance differences, ankle and knee joint moments were similar for both VR types and FW, while FW produced greater hip and lumbar spine moments (p < 0.05). Free-weight resistance also produced greater eccentric lumbopelvis moments than EVR (p < 0.05). Comparing VR types, CVR produced greater concentric hip, lumbopelvis, and lumbar spine moments than EVR (p < 0.05). Both VR conditions produced greater knee concentric power than FW, while CVR also produced greater hip power than FW (p < 0.05). These findings suggest that CVR may be preferential to EVR for increased power adaptation. In addition, for those prone to lumbar injuries, EVR may be preferential because it provides sufficient lower limb stimulation while decreasing spinal loading.