Abstract
Purpose: Identify acute effects of a single accentuated eccentric (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 four protocols (sets*repetitions@eccentric/concentric): AEL65, 3*5@120/65% one-repetition maximum (1-RM); AEL80, 3*3@120/80% 1-RM; TRA65, 3*5@65/65% 1-RM; TRA80, 3*3@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=0.012), concentric peak force (187.8+-284.4 N; p=0.007), eccentric mean power (-145.2+-62.0 W; p=0.028) and eccentric peak power (-328.6+-93.7 W; p=0.002) during AEL65 were significantly greater than TRA65. When collapsed across repetitions, AEL65 resulted in slower eccentric velocity and power during repetition one, but faster eccentric and concentric velocity and power in subsequent repetitions (p<=0.036).
When comparing AEL80 to TRA80, concentric peak force (133.8+-56.9 N; p=0.029), eccentric mean power (-83.57+-38.0 W; p=0.040), and eccentric peak power (-242.84+-67.3 W; p=0.002) 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.