Acute Effects of Accentuated Eccentric Loading in Comparison to Traditional Resistance Loading on Velocity and Other Parameters in Concentric and Eccentric Phases in Barbell Back Squat

Najafi, A, Nosaka, K, Javidi, M, Naddafha, S, Kumagawa, D, Bertochi, GFA, and Latella, C. Acute effects of accentuated eccentric loading in comparison to traditional resistance loading on velocity and other parameters in concentric and eccentric phases in barbell back squat. J Strength Cond Res XX(X): 000-000, 2026-We investigated the acute effects of accentuated eccentric loading (AEL) vs. traditional resistance loading (TRL) on concentric and eccentric velocities and related parameters during barbell back squat (BBS). We hypothesized that AEL at 85% or 100% of 1 repetition maximum (1RM) in the first eccentric repetition would enhance the concentric velocity in subsequent repetitions. Fourteen resistance-trained men (age: 28.9 ± 7.8 years, body mass: 83.7 ± 9.4 kg, BBS 1RM/body mass ratio: 1.42 ± 0.23) completed TRL BBS at 65% 1RM, followed by BBS with AEL85 (85%/65% 1RM for eccentric/concentric) and AEL100 (100%/65% 1RM) in a randomized order. Each protocol consisted of 3 sets of 5 repetitions. One additional TRL set was performed at the end to examine fatigue. The rating of perceived exertion (RPE; 0-10 scale) was recorded after each set. Concentric peak and mean velocity, force, and power, along with eccentric mean and peak velocity, and peak force and power in each repetition were obtained using GymAware PowerTool. A 3-way repeated-measures ANOVA showed no significant differences between the 3 protocols for changes in the outcome measures over repetitions and sets. Across all sets and protocols, concentric mean velocity (mean ± SD) was lowest in the first repetition (0.61 ± 0.09 m·s-1), increased in the second (0.68 ± 0.07), peaked in the third (0.69 ± 0.07), and decreased in the fourth (0.67 ± 0.08) and fifth repetitions (0.65 ± 0.09). RPE (mean ± SD) was highest in AEL100 (8.5 ± 0.9), followed by AEL85 (8.0 ± 1.1) and TRL (6.9 ± 1.1), with all protocols differing significantly from one another. These indicate that AEL did not affect velocity-related measures in moderately resistance-trained individuals.