Effect of Acute Low-load High-repetition Resistance Exercise on Protein Synthetic Signaling Pathway and Satellite Cell Activation in Skeletal Muscle of Rats

Abstract

PURPOSE: Previous studies have reported that low-load high-repetition (LLHR) resistance exercise can induce muscle hypertrophy to a similar extent as high-load low-repetition (HLLR). However, it is unclear which mechanical stress, such as exercise intensity, contraction number, and/or total work volume and which molecular mechanisms underpin the greater relative muscle hypertrophy after LLHR exercise.METHODS: Sprague-Dawley rats (12 weeks, N=35) were randomly allocated into control (Con, n=7), low-load low-repetition (LLLR, n=7), low-load medium-repetition (LLMR, n=7), LLHR (n=7), and HLLR (n=7) resistance exercise groups. They performed a ladder climbing exercise to evaluate the effect of exercise intensity, contraction number and work volume on the activation of satellite cells and protein synthesis signaling pathway.RESULTS: The number of active satellite cells and the phosphorylation of mTOR, p70S6K, ERK, and p38 were increased after LLHR and HLLR exercise (<i>p</i><.005). However, phosphorylation of 4E-BP1 was only increased after the LLHR exercise (<i>p</i><.05).CONCLUSIONS: Acute low load exercise accompanied by high total work volume may activate muscle protein synthesis mechanisms for hypertrophy similar to high load resistance exercise.