“You need to train each muscle at least twice a week to build muscle.”
Training a muscle once a week builds about as much muscle as training it more often, when total weekly sets are the same.
A once-a-week session for a muscle can build muscle well, so a busy schedule is no reason to skip lifting. What counts is the total number of hard sets each muscle gets over the week. Splitting those sets across two or more days is a handy way to fit more of them in, and it helps strength, but it is a choice, not a rule.
Plan your week by counting the hard sets each muscle gets, then spread them over whatever days you can actually train.
A 25-study meta-analysis and a 67-study analysis found that how often you train a muscle makes little or no difference to growth once the total weekly work is the same. Confidence is moderate because the trials are small and mostly in young men, and an earlier, smaller review did favor twice a week.
Training a muscle once a week builds about as much muscle as training it more often, when total weekly sets are the same. In 25 studies comparing training frequencies, growth did not differ when total weekly work was matched, including in people who already lift. The grain of truth: when extra sessions added extra sets, more frequent training built slightly more muscle.
An earlier review of 10 studies, published in 2016, found that training a muscle twice a week built more muscle than once a week and advised at least twice a week. The later 2019 review of 25 studies, by the same lead author, did not confirm this when total work was matched, and concluded that people can choose how often to train each muscle "based on personal preference." A 2026 analysis of 67 studies with 2,058 people found frequency's effect on muscle growth was compatible with having no real effect, while more frequent training did help strength. US activity guidelines advise muscle-strengthening activities on 2 or more days a week for overall health, a separate goal from maximum muscle growth.
- Schoenfeld BJ, Grgic J, Krieger J. How many times per week should a muscle be trained to maximize muscle hypertrophy? A systematic review and meta-analysis of studies examining the effects of resistance training frequency. Journal of Sports Sciences. 2019;37(11):1286-1295. DOI: 10.1080/02640414.2018.1555906. PMID: 30558493
- Pelland JC, Remmert JF, Robinson ZP, Hinson SR, Zourdos MC. The Resistance Training Dose Response: Meta-Regressions Exploring the Effects of Weekly Volume and Frequency on Muscle Hypertrophy and Strength Gains. Sports Medicine. 2026;56(2):481-505. DOI: 10.1007/s40279-025-02344-w. PMID: 41343037
- Schoenfeld BJ, Ogborn D, Krieger JW. Effects of Resistance Training Frequency on Measures of Muscle Hypertrophy: A Systematic Review and Meta-Analysis. Sports Medicine. 2016;46(11):1689-1697. DOI: 10.1007/s40279-016-0543-8. PMID: 27102172
- US Centers for Disease Control and Prevention. Adult Activity: An Overview. Dec. 20, 2023