Effects of Varying Load Intensity on Skeletal Muscle Damage Between Two Isovolumic Resistance Exercise Bouts

Abstract

There are limited data comparing the efficacy of resistance loads within the hypertrophy range for promoting muscular growth, particularly when similar training volumes are utilized. The purpose of this study was to determine if two similar volume-loads, utilizing different intensities, would produce dissimilar muscular damage and inflammation. Eleven resistance-trained, college-aged males participated in this study. After testing 1RM barbell squats, participants completed two similar volume-load barbell squat sessions at two different resistance loads (67% and 85% of 1RM) on two separate visits. Venous blood samples were collected at baseline and one hour after completion of each exercise session. Plasma was isolated and analyzed for myoglobin and C-reactive protein (CRP) expression via ELISA. Plasma myoglobin expression was significantly elevated above baseline (BASE) values only after the 85% of 1RM (HHL) session (p =0.031), though the 67% (LHL) trial (p = 0.054; η² = 0.647) was approaching significance (BASE: 1.42±.12 ng/mL; LHL: 4.65±1.13 ng/mL; HHL: 5.00±1.01 ng/mL). No changes in plasma CRP were observed. Despite attempts to equate volumes between resistances, mean total volume-load was significantly higher during the 67% of 1RM trial than during the 85% trial. Resistance loads at 85% of 1RM inflict significantly increased muscle damage over baseline values, even when significantly less total volume was lifted during the 85% trial. Individuals looking to maximize strength and hypertrophy during general training or during rehabilitation may benefit from these findings when determining the appropriate training load.

Keywords: Resistance training; hypertrophy; inflammation; muscle damage; volume-matched.

Figure 1

Outline of Study Protocol and Events

Figure 2. Plasma Myoglobin and CRP

a. Plasma myoglobin protein expression for baseline, LHL, and HHL. b. Plasma CRP protein expression for Base, LHL, and HHL. * indicates significant difference from Base (p< 0.05). Bar graph data represents mean value ± SEM.

Figure 3. Total Weight Lifted

Mean total weight lifted for LHL and HHL. # indicates significant difference from other trial (p< 0.05). Bar graph data represents mean value ± SEM.