Purpose: To identify acute effects of a single accentuated eccentric loading (AEL) repetition on subsequent back-squat kinetics and kinematics with different concentric loads.
Methods: Resistance-trained men (N = 21) participated in a counterbalanced crossover design and completed 4 protocols (sets × repetitions at eccentric/concentric) as follows: AEL65, 3 × 5 at 120%/65% 1-repetition maximum (1-RM); AEL80, 3 × 3 at 120%/80% 1-RM; TRA65, 3 × 5 at 65%/65% 1-RM; and TRA80, 3 × 3 at 80%/80% 1-RM. During AEL, weight releasers disengaged from the barbell after the eccentric phase of the first repetition and remained off for the remaining repetitions. All repetitions were performed on a force plate with linear position transducers attached to the barbell, from which eccentric and concentric peak and mean velocity, force, and power were derived.
Results: Eccentric peak velocity (-0.076 [0.124] m·s-1; P = .01), concentric peak force (187.8 [284.4] N; P = .01), eccentric mean power (-145.2 [62.0] W; P = .03), and eccentric peak power (-328.6 [93.7] W; P < .01) during AEL65 were significantly greater than TRA65. When collapsed across repetitions, AEL65 resulted in slower eccentric velocity and power during repetition 1 but faster eccentric and concentric velocity and power in subsequent repetitions (P ≤ .04). When comparing AEL80 with TRA80, concentric peak force (133.8 [56.9] N; P = .03), eccentric mean power (-83.57 [38.0] W; P = .04), and eccentric peak power (-242.84 [67.3] W; P < .01) were enhanced.
Conclusions: Including a single supramaximal eccentric phase of 120% 1-RM increased subsequent velocity and power with concentric loads of 65% 1-RM, but not 80% 1-RM. Therefore, AEL is sensitive to the magnitude of concentric loads, which requires a large relative difference to the eccentric load, and weight releasers may not need to be reloaded to induce performance enhancement.
Keywords: kinematics; kinetics; power; velocity; weight releasers.