Abstract
The present study was undertaken to test the hypothesis that the contraction mode of action [static-isometric (Iso), shortening-concentric (Con), or lengthening-eccentric (Ecc)] used to stress the muscle provides a differential mechanical stimulus eliciting greater or lesser degrees of anabolic response at the initiation of a resistance training program. We performed an acute resistance training study in which different groups of rodents completed four training sessions in either the Iso, Con, or Ecc mode of contraction under conditions of activation and movement specifically designed to elicit equivalent volumes of force accumulation. The results of this experiment indicate that the three modes of contraction produced nearly identical cell signaling, indicative of an anabolic response involving factors such as increased levels of mRNA for IGF-I, procollagen III alpha1, decreased myostatin mRNA, and increased total RNA concentration. The resulting profiles collectively provide evidence that pure mode of muscle action, in and of itself, does not appear to be a primary variable in determining the efficacy of increased loading paradigms with regard to the initiation of selected muscle anabolic responses.
Highlights
Title Similar acute molecular responses to equivalent volumes of isometric, lengthening, or shortening mode resistance exercise
In a recent study focused on muscle atrophy, we found that isometric exercise was ineffective at eliminating the initial muscle atrophy associated with 5 days of unloading [24]
The primary goal of this study was to test the hypothesis that a particular muscle action mode is more effective at initiating muscle anabolic responses at the onset of training
Summary
Title Similar acute molecular responses to equivalent volumes of isometric, lengthening, or shortening mode resistance exercise. Observations of the regulatory steps leading to increased protein translation and decreased degradation have enhanced our understanding of key processes that govern protein balance in response to increased loading in skeletal muscle This understanding has not been extensively applied as a scientific basis for selecting specific resistance exercise training parameters such as mode of action [e.g., static-isometric (Iso), shortening-concentric (Con), or lengthening-eccentric (Ecc) or combinations thereof] to elicit an anabolic state. We were interested in determining whether, during the initial stages of a resistance training program, there are differences in the responses of skeletal muscles based on the mode of muscle action (e.g., Iso vs Con vs Ecc) If this were the case, it might suggest that a particular muscle action could be more effective in preventing atrophy at the critical early time point at the initiation of muscle unloading. That study did not provide any data on the initial period of muscle adaptation that might be critical for effective countermeasures at the onset of unloading
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