In resistance training for muscle growth, or hypertrophy, people often advise you to train to failure on every set. However, in the contemporary wave of ‘science-based lifting,’ a different repetition scheme may be more effective in programs: a five-repetition maximum with one repetition in reserve.

Training to task failure, or until you can no longer perform another repetition, is excellent because it recruits type II muscle fibers, which have the most growth potential, and provides a greater hypertrophy stimulus than training further from failure. In more technical terms, as effort increases and concentric contraction velocity decreases, motor unit recruitment (MUR) and single-fiber mechanical tension increase, respectively. This is ideal for hypertrophy, as seen in a recent 2023 meta-regression conducted by Robinson et al: “the findings suggest a meaningful relationship between proximity to failure and changes in muscle size whereby muscle hypertrophy tends to increase as sets are performed closer to failure” [1]. In other words, training close to failure was significantly correlated with more muscle growth.

However, data have shown that leaving two repetition in reserve when lifting moderate loads virtually eliminates post-workout reductions in force, indicating a significant decrease in muscle damage when training with two repetition in reserve [2]. Effectively, with moderate loads, the last two repetitions cause the majority of muscle damage. That said, knowing muscle damage is counterproductive to hypertrophy [3, 4] and that heavier loads induce less muscle damage than light/moderate loads per set taken to failure [5, 6, 7], it would therefore be most efficient to train with heavy loads that makes you fail on the fifth repetition. Why five repetitions specifically? It is because, after accounting for bedridden/sarcopenic outliers from Robinson et al. (2023) [1], the five repetitions at the end of a set to failure were the ones that actually stimulated significant hypertrophy. 

However, rather than performing five repetitions to failure on every set, there may be value in leaving one repetition in reserve to further reduce muscle damage and make subsequent sets in the workout more effective. This is because the final repetition in a set to failure causes the most muscle damage [2, 8], and muscle damage reduces single-fiber mechanical tension [9, 10, 11] and central motor command via negative afferent feedback [12, 13, 14].

 For example, if you were to perform a biceps curl for five repetitions to failure, the subsequent set of bicep curls would yield lesser results than the previous due to local and non-local fatigue. Similarly, if you were to later perform a set of tricep pushdowns, that set for triceps would also be negatively affected because of the central nervous system (non-local) fatigue produced by the sets of bicep curls to failure [15]. Both of these examples, where the second set is less effective than the first, could be somewhat ameliorated if, rather than performing the first set of bicep curls to failure, you simply left one repetition in reserve to reduce muscle damage.

All in all, performing most of your sets with a five-repetition max with one repetition in reserve is likely most effective. In doing so, you may be sacrificing one stimulating repetition, but it is likely worth it to make the subsequent sets––whether they are for the same muscle or not––more effective.