Back squat and deadlift fatiguing protocols elicit distinct countermovement jump profiles: phase-specific predictors and soreness responses

Introduction or background: Residual fatigue following resistance exercise can impair neuromuscular performance. The back squat (BSQ) and deadlift (DL) are key lower-limb exercises but may differ in their fatigue and recovery profiles. Identifying phase-specific markers during the countermovement jump (CMJ) may improve monitoring and guide recovery strategies. Sources of data: Fifty-four resistance-trained adults (≥1 year experience) were randomly assigned to BSQ, DL, or control (CON) groups. After one-repetition maximum (1RM) estimation, BSQ and DL completed a fatiguing protocol (3 × 12 repetitions at 70% 1RM). CMJ performance was assessed at baseline, immediately, 30 min, and 24 h post-exercise using a force platform. Phase-specific force-time variables and the modified reactive strength index (RSImod) were calculated; muscle soreness was recorded at 24 and 48 h. Areas of agreement: Both BSQ and DL caused significant decrements in CMJ-derived metrics, as indicated by a linear mixed-effects model, and greater soreness than control, according to a two-way mixed analysis of variance (ANOVA). BSQ produced larger and earlier impairments across force, displacement, and work variables, whereas DL showed smaller but more persistent reductions in braking rate of force development (RFD) and RSImod. Areas of controversy: Despite similar soreness, recovery patterns differed, indicating distinct neuromuscular demands and time courses between exercises. Growing points: Phase-specific CMJ metrics particularly braking and unloading RFD, eccentric/concentric work, and RSImod are sensitive indicators of residual fatigue. Areas timely for developing research: Future studies should integrate electromyographic and biochemical markers and extend observation beyond 48 h to describe full recovery trajectories.