Hypertrophic effects of concentric versus eccentric muscle actions: A systematic review and meta-analysis.

Abstract

Controversy exists as to whether different dynamic muscle actions produce divergent hypertrophic responses. The purpose of this paper was to conduct a systematic review and meta-analysis of randomized controlled trials comparing the hypertrophic effects of concentric versus eccentric training in healthy adults following regimented resistance training (RT). Studies were deemed eligible for inclusion if they met the following criteria: 1) were an experimental trial published in an English-language refereed journal; 2) directly compared concentric and eccentric actions without the use of external implements (i.e. blood pressure cuffs) and all other RT variables equivalent; 3) measured morphologic changes via biopsy, imaging (magnetic resonance imaging, computerized tomography, or ultrasound), bioelectrical impedance, and/or densitometry; 4) had a minimum duration of 6 weeks; and, 5) used human participants without musculoskeletal injury or any health condition that could directly, or through the medications associated with the management of said condition, be expected to impact the hypertrophic response to resistance exercise. A systematic literature search determined that 15 studies met inclusion criteria. Results showed that eccentric muscle actions resulted in a greater effect size (ES) compared to concentric actions, but results did not reach statistical significance (ES difference = 0.25 ± 0.13; CI95: -0.03, 0.52; P = 0.076). The mean percent change in muscle growth across studies favored eccentric compared to concentric actions (10.0% vs 6.8, respectively). The findings indicate the importance of including eccentric and concentric actions in a hypertrophy-oriented RT program as both have shown to be effective in increasing muscle hypertrophy.