Resistance training frequency and skeletal muscle hypertrophy: A review of available evidence

OBJECTIVES: Current reviews and position stands on resistance training (RT) frequency and associated muscular hypertrophy are based on limited evidence holding implications for practical application and program design. Considering that several recent studies have shed new light on this topic, the present paper aimed to collate the available evidence on RT frequency and the associated effect on muscular hypertrophy. DESIGN: Review article. METHODS: Articles for this review were obtained through searches of PubMed/MEDLINE, Scopus, and SPORTDiscus. Both volume-equated (studies in which RT frequency is the only manipulated variable) and non-volume-equated (studies in which both RT frequency and volume are the manipulated variables) study designs were considered. RESULTS: Ten studies were found that used direct site-specific measures of hypertrophy, and, in general, reported that RT once per week elicits similar hypertrophy compared to training two or three times per week. In addition, 21 studies compared different RT frequencies and used lean body mass devices to estimate muscular growth; most of which reported no significant differences between training frequencies. Five studies were identified that used circumference for estimating muscular growth. These studies provided findings that are difficult to interpret, considering that circumference is a crude measure of hypertrophy (i.e., it does not allow for the differentiation between adipose tissue, intracellular fluids, and muscle mass). CONCLUSIONS: Based on the results of this review, it appears that under volume-equated conditions, RT frequency does not seem to have a pronounced effect of gains in muscle mass