Inter-set rest duration and repetition performance in single-joint resistance exercise: a dose-response synthesis of eight acute studies

How long to rest between sets is a routine programming decision, yet for single-joint (isolation) exercise the acute dose–response between rest duration and repetition performance has not previously been fittable: in our prior analysis only one eligible study (Miranda et al., 2009) was available, so no dose–response could be fitted at all. We assembled a pool of eight acute studies that directly measured repetition performance in single-joint exercise across inter-set rest durations of 1–5 min (26 within-arm contrasts) and fitted dose–response models of several shapes, with a unimodality-constrained two-piece isotonic fit as the headline. Repetition performance rose with rest duration: gains at 4–5 min versus 1 min were approximately +38–45% repetitions. All monotone shapes (linear, log, square-root, reciprocal) peaked at the 5-min edge of the tested range, the quadratic peaked at 4.89 min, and the headline isotonic fit peaked at 4.0 min. That 4.0-min headline is fragile, however: the pool's only 4-min doses come from a single study (Senna et al., 2016, n = 10), no arm in any study measured both 4 and 5 min, and dropping that study moves the isotonic peak to 5.0 min (monotone). The defensible summary is therefore that repetition performance rises up to the 4–5 min region, with the peak unlocalized between 4 and 5 min, on evidence we rate as thin. This note concerns acute repetition performance only and makes no hypertrophy claim.