Abstract
The aim of this study was to investigate the effects of an augmented eccentric load upon the kinematics and muscle activation of bench press, and to investigate possible mechanisms behind augmented eccentric loading during the lift. Sixteen resistance-trained males (age 28.5 ± 7.7 years, height 1.78 ± 0.08 m, body mass 80.7 ± 14.3 kg) performed three repetitions at 95/85% of 1RM (augmented eccentric loading), and 85/85% of 1RM (control) in bench press, while barbell kinematics and muscle activation of eight muscles were measured. The main findings were that no kinematic differences between the augmented and control condition were found, only an effect of repetition. Furthermore, augmented loading caused a higher activation of the biceps brachii during the pre-sticking and sticking region, while a lower activation in the sternal part of pectoralis major during the eccentric phase was observed. Based on the present findings, it can be concluded that augmented eccentric loading with 95% of 1RM in bench press did not have any acute positive effect upon the concentric phase of the lift (85% of 1RM) and that the proposed underlying mechanisms like potentiation, increased neural stimulation and preload, and recovery of stored elastic energy does not seem to occur with these loads.
Highlights
A muscle undergoes two phases during contraction; the eccentric phase followed by the concentric phase
A significant effect of condition was found for the peak eccentric velocity (F = 5.4, p = 0.034, η2 = 0.27) and time of occurrence of this event (F = 6.9, p = 0.019, η2 = 0.31) with a lower peak eccentric velocity occurring earlier for the augmented eccentric condition compared with the control condition
Post hoc comparisons revealed that the total eccentric phase was significantly longer in repetition 1 compared to the other repetitions in the control condition
Summary
A muscle undergoes two phases during contraction; the eccentric (muscle lengthening) phase followed by the concentric (muscle shortening) phase. Numerous studies have compared the efficacy of a loaded eccentric phase using an additional 20–30% of body mass on a drop jump, which led to an increase in subsequent jump height in (highly) trained athletes [7,8]. Higher loading during the eccentric phase may increase force production due to an enhanced synaptic excitation in the spinal cord. This leads to greater post synaptic potential, increasing the force production capacity of the involved muscle groups, which is known as potentiation [10]. Nardone; Romano; Schieppati [11] demonstrated that during eccentric contractions, selective recruitment of high threshold motor units was possible and that this lead to greater concentric force production by the contribution of larger motor unit pools. Walker; Blazevich; Haff; Tufano; Newton; Hakkinen [12] reported that an increase in voluntary muscle activation in the vastus lateralis following an augmented eccentric load led to greater isometric strength compared to traditional loading after a 10-week protocol in strength-trained men
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