Do partial reps work?
Yes, especially at the stretched end: partials where the muscle is long grow it about as well as full reps, and better than partials at the top.
The old rule was full range or nothing. What the research actually shows is that the stretched half of the movement does most of the work: a half rep from the bottom beats a half rep from the top, and often matches a full rep.
Practical use: keep full range as the default, because it is simplest and it trains the whole muscle. Then use lengthened partials at the end of a set, when you can no longer complete full reps, to squeeze a few more hard reps out of the muscle.
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Sources
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- Wolf, M. et al. (2023). Partial vs full range of motion resistance training: a systematic review and meta-analysis. Int J Strength Cond 3(1). Full range came out ahead overall, with the gap closing when the partial range covered the stretched position.
- Maeo, S. et al. (2021). Greater hamstrings muscle hypertrophy but similar damage protection after training at long versus short muscle lengths. Med Sci Sports Exerc 53(4). Training a muscle in its lengthened position grew it more than training it short.
- Maeo, S. et al. (2023). Triceps brachii hypertrophy is substantially greater after elbow extension training performed in the overhead versus neutral arm position. Eur J Sport Sci 23(7). Same muscle, same exercise, more growth when the arm position put the triceps on stretch.