Antioxidant vitamin supplementation on muscle adaptations to resistance training: A double-blind, randomized controlled trial

Abstract

Objectives: The aim of this study was to examine whether antioxidant vitamin supplementation with vitamin C (VitC) and vitamin E (VitE) affects the hypertrophic and functional adaptations to resistance training in trained men. Methods: This was a double-blind, randomized controlled trial in which participants were supplemented daily with VitC and VitE ( n = 12) or placebo ( n = 11) while completing a 10-wk resistance training program accompanied by a dietary intervention (300 kcal surplus and adequate protein intake) designed to optimize hypertrophy. Body composition (dual-energy x-ray absorptiometry), handgrip strength, and one-repetition maximum (1-RM), maximal force (F0), velocity (V0), and power (Pmax) were measured in bench press (BP) and squat (SQ) tests conducted before and after the intervention. To detect between-group differences, multiple-mixed analysis of variance, standardized differences, and qualitative differences were estimated. Relative changes within each group were assessed using a paired Student's t test. Results: In both groups, similar improvements were produced in BP 1-RM , SQ 1-RM SQ, and BP F0 (P < 0.05) after the resistance training program. A small effect size was observed for BP 1-RM (d = 0.53), BP F0 (d = 0.48), and SQ 1-RM (d = –0.39), but not for SQ F0 (d = 0.03). Dominant handgrip strength was significantly increased only in the placebo group (P < 0.05). According to body composition data, a significant increase was produced in upper body fat-free mass soft tissue (FFMST; P < 0.05) in the placebo group, whereas neither total nor segmental FFMST was increased in the vitamin group. Small intervention effect sizes were observed for upper body FFSMT (d = 0.32), non-dominant and dominant leg FFMST (d = –0.39; d = –0.42). Although a significant increase in total body fat was observed in both groups (P < 0.05) only the placebo group showed an increase in visceral adipose tissue (P < 0.05), showing a substantial intervention effect (d = 0.85). Conclusions: The data indicated that, although VitC/VitE supplementation seemed to blunt upper body strength and hypertrophy adaptations to resistance training, it could also mitigate gains in visceral adipose tissue elicited by an energy surplus.