Abstract
We compared the effects of accentuated eccentric loading (AEL) on mechanical variables and agonist muscle activation using low (30% 1-repetition maximum (1RM)) and high (80% 1RM) upward-phase loading with AEL (100% 1RM during downward phase) to traditional loading schemes (T) in the bench press. Twelve resistance-trained men (26 ± 6 years; 1RM: 134 ± 33 kg) performed sets of two repetitions with three-minute intervals using loading schemes of 30AEL, 30T, 80AEL, and 80T. AEL was applied using weight releasers while force plates and a 3D motion-analysis system were used to measure mechanical variables. Electromyographic activity of the pectoralis major and triceps brachii muscles was also recorded. The greater downward-phase loads experienced during the AEL conditions allowed greater overall mean vertical forces (mean difference (Diff): 118 N, p < 0.001), greater work (Diff: 43 J, p < 0.001), and greater pectoralis major muscle activation (Diff: 27 µV, p = 0.002) compared to the corresponding traditional loading schemes. However, there was little evidence of potentiation of the mechanical variables or muscle activity during the subsequent upward phases caused by the AEL schemes. It is possible that the use of weight releasers may disrupt lifting technique particularly during low AEL schemes thereby diminishing any benefits.
Highlights
The acute mechanical, metabolic, and hormonal responses to resistance training exercises have been proposed to drive neuromuscular adaptations that support the long-term enhancement of muscular strength and power [1,2,3]
It is known that the acute mechanical, neural, metabolic, and hormonal characteristics differ between eccentric muscle actions and those observed during concentric actions; eccentric muscles actions are associated with greater tension development, greater cortical excitability despite lower motor unit activity, reduced energy per unit work, greater upregulation of satellite cells, and possibly larger IGF-I responses compared to concentric muscle actions [5]
The loads for 30AEL and 80AEL were 30% and 80% 1-repetition maximum (1RM), respectively, for the upward phase with a constant load of 100% 1RM applied during the downward phase using mechanical weight releasers
Summary
The acute mechanical, metabolic, and hormonal responses to resistance training exercises have been proposed to drive neuromuscular adaptations that support the long-term enhancement of muscular strength and power [1,2,3]. Typical resistance training exercises used to develop muscular strength and power, such as the back squat and bench press, incorporate the combination of eccentric actions followed by concentric actions associated with the stretch shortening cycle as the load is lowered and raised during each repetition. The selection of loads used during typical resistance training exercises is based upon the concentric capabilities of the athlete (i.e., the load that can be raised during a given exercise) This constraint on load selection has led to the proposal that practitioners should endeavor to utilize methods to sufficiently overload the downward
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