Resistance training volume in trained individuals: can larger increases promote smaller muscular adaptations?

Abstract

To ensure continuous skeletal muscle hypertrophy throughout a resistance training (RT) program, it is recommended that the prescription follows the principle of progressive overload. One way to ensure progressive overload is by manipulating RT variables, such as volume (number of weekly sets per muscle group). Although the optimal magnitude of volume progression for maximizing muscle hypertrophy is not yet defined, it is suggested that large and abrupt progressions may impair RT-induced skeletal muscle hypertrophy due to an increased proteolytic response. However, this hypothesis still needs confirmation. Therefore, the aims of the present study are: (1) to verify whether 120% increases in previously performed volume (VOL120) may attenuate fiber and muscle hypertrophic responses compared to 20% increases (VOL20); (2) to acutely and chronically compare the behavior of muscle proteolysis biomarkers (ubiquitin-proteasome and calpain pathways) between the experimental protocols. In a within-subject and single-blind design, 30 subjects (15 women and 15 men) will have their legs randomized into one of the experimental conditions (VOL120 vs. VOL20). The cross-sectional area of the fibers (immunohistochemistry) and the vastus lateralis muscle (ultrasonography) will be assessed. Additionally, the expression of proteins involved in the ubiquitin-proteasome (MuRF-1, Atrogin-1, FOXO1, FOXO3, 20S proteasome) and calpain (isoforms 1, 2, and 3) proteolytic pathways will be analyzed using Western Blotting. It is expected that the 120% progression in RT volume will result in attenuated muscle hypertrophy compared to a 20% progression in weekly volume. In this regard, it is also expected that the 120% volume progression will elicit a greater acute and chronic response of proteolytic biomarkers compared to the lower magnitude progression.