Rest between sets and muscle growth
Across 9 randomized-design studies contributing 19 measurements of lean/muscle mass in healthy adults, the controlled head-to-head comparisons of short versus longer inter-set rest all had credible intervals spanning zero: central estimates tended to favor longer rest at the arm and thigh, while the whole-body estimate was closer to zero and marginally favored shorter rest. Heterogeneity in the pooled results was substantial. The authors conclude that the results suggest a small hypertrophic benefit to employing inter-set rest interval durations >60 s, perhaps mediated by reductions in volume load, but that their analysis did not detect appreciable differences in hypertrophy when resting >90 s between sets.
Singer A (2024) · Frontiers in sports and active living · PMID 39205815
It does NOT say longer rest produces meaningfully more muscle. Every controlled head-to-head estimate has a credible interval crossing zero, so the direction is a lean, not a resolved difference.
It says NOTHING about STRENGTH. The word "strength" does not appear anywhere in the abstract — I string-searched the re-fetched text. The measured outcome is lean/muscle mass only. This claim cannot support any 1RM, maximal-strength, or "rest longer for strength" recommendation, and must never be used to build a strength card.
The ">60 s" figure is the authors' interpretive conclusion, not a pooled estimate. No analysis in the abstract reports a 60-second breakpoint; it is their reading of the pattern. Attribute it, never render it as a measured threshold.
The ">90 s" finding is an absence of detection, not proven equivalence. "Did not detect appreciable differences" with 9 studies and acknowledged substantial heterogeneity is weak evidence of no effect, not evidence of no effect.
It does not establish an optimal rest duration or an upper bound, and does not show that resting under 60 s blunts growth in any individual lifter.
It must not be presented as a finding about trained lifters. The abstract says only "healthy adults" and reports no training-status, sex, or age breakdown.
The two headline SMDs of 0.48 and 0.56 are NON-CONTROLLED pre-to-post gains within each condition, not a short-versus-longer contrast. Putting them side by side as though the gap between them were the effect would be a serious misreading; the actual contrasts are the much smaller controlled estimates.
With 9 studies, no reported participant total, no reported training duration, and substantial acknowledged heterogeneity, this is a directional synthesis, not a settled dose-response curve.
Every figure below is shown with the sentence it was taken from, so you can check it against the paper rather than trusting us.
- 9studies
Number of randomized-design studies meeting inclusion criteria
Bayesian meta-analyses on non-controlled effect sizes using hierarchical models of all 19 measurements (thigh: 10; arm: 6; whole body: 3) from 9 studies meeting inclusion criteria analyses showed substantial overlap of standardized mean differences across the different inter-set rest periods [binary: short: 0.48 (95%CrI: 0.19-0.81), longer: 0.56 (95%CrI: 0.24-0.86); Four categories: short: 0.47 (95%CrI: 0.19-0.80), intermediate: 0.65 (95%CrI: 0.18-1.1), long: 0.55 (95%CrI: 0.15-0.90), very long: 0.50 (95%CrI: 0.14-0.89)], with substantial heterogeneity in results.
- 19measurements
Total muscle-size measurements pooled across the 9 included studies
Bayesian meta-analyses on non-controlled effect sizes using hierarchical models of all 19 measurements (thigh: 10; arm: 6; whole body: 3) from 9 studies meeting inclusion criteria analyses showed substantial overlap of standardized mean differences across the different inter-set rest periods [binary: short: 0.48 (95%CrI: 0.19-0.81), longer: 0.56 (95%CrI: 0.24-0.86); Four categories: short: 0.47 (95%CrI: 0.19-0.80), intermediate: 0.65 (95%CrI: 0.18-1.1), long: 0.55 (95%CrI: 0.15-0.90), very long: 0.50 (95%CrI: 0.14-0.89)], with substantial heterogeneity in results.
- 0.48 (95%CrI: 0.19-0.81)standardized mean difference, non-controlled pre-to-post
Muscle-size gain with SHORT inter-set rest in the binary comparison. Non-controlled (within-arm pre-to-post), so this is growth achieved under short rest, NOT short rest's advantage over anything.
Bayesian meta-analyses on non-controlled effect sizes using hierarchical models of all 19 measurements (thigh: 10; arm: 6; whole body: 3) from 9 studies meeting inclusion criteria analyses showed substantial overlap of standardized mean differences across the different inter-set rest periods [binary: short: 0.48 (95%CrI: 0.19-0.81), longer: 0.56 (95%CrI: 0.24-0.86); Four categories: short: 0.47 (95%CrI: 0.19-0.80), intermediate: 0.65 (95%CrI: 0.18-1.1), long: 0.55 (95%CrI: 0.15-0.90), very long: 0.50 (95%CrI: 0.14-0.89)], with substantial heterogeneity in results.
- 0.56 (95%CrI: 0.24-0.86)standardized mean difference, non-controlled pre-to-post
Muscle-size gain with LONGER inter-set rest in the binary comparison. Its interval overlaps the short-rest estimate substantially; the two must never be presented as a difference.
Bayesian meta-analyses on non-controlled effect sizes using hierarchical models of all 19 measurements (thigh: 10; arm: 6; whole body: 3) from 9 studies meeting inclusion criteria analyses showed substantial overlap of standardized mean differences across the different inter-set rest periods [binary: short: 0.48 (95%CrI: 0.19-0.81), longer: 0.56 (95%CrI: 0.24-0.86); Four categories: short: 0.47 (95%CrI: 0.19-0.80), intermediate: 0.65 (95%CrI: 0.18-1.1), long: 0.55 (95%CrI: 0.15-0.90), very long: 0.50 (95%CrI: 0.14-0.89)], with substantial heterogeneity in results.
- 0.13 (95%CrI: -0.27 to 0.51)standardized mean difference, controlled short vs. longer
Head-to-head arm hypertrophy difference, central estimate leaning toward longer rest. Credible interval crosses zero.
Univariate and multivariate pairwise meta-analyses of controlled binary (short vs. longer) effect sizes showed similar results for the arm and thigh with central estimates tending to favor longer rest periods [arm: 0.13 (95%CrI: -0.27 to 0.51); thigh: 0.17 (95%CrI: -0.13 to 0.43)].
- 0.17 (95%CrI: -0.13 to 0.43)standardized mean difference, controlled short vs. longer
Head-to-head thigh hypertrophy difference, central estimate leaning toward longer rest. Credible interval crosses zero.
Univariate and multivariate pairwise meta-analyses of controlled binary (short vs. longer) effect sizes showed similar results for the arm and thigh with central estimates tending to favor longer rest periods [arm: 0.13 (95%CrI: -0.27 to 0.51); thigh: 0.17 (95%CrI: -0.13 to 0.43)].
- -0.08 (95%CrI: -0.45 to 0.29)standardized mean difference, controlled short vs. longer
Head-to-head whole-body lean mass difference, marginally favouring SHORTER rest — the one estimate pointing the other way. Credible interval crosses zero.
In contrast, central estimates closer to zero but marginally favoring shorter rest periods were estimated for the whole body [whole body: -0.08 (95%CrI: -0.45 to 0.29)].
- >60 sseconds of inter-set rest
The rest duration above which the AUTHORS CONCLUDE a small hypertrophic benefit. This is their interpretive conclusion, not a pooled estimate reported anywhere in the abstract — it must always be attributed as 'the authors conclude', never rendered as a measured cutoff. NOTE ON WHITESPACE: in the source, the space between '60' and 's' is U+2005 FOUR-PER-EM SPACE, not an ASCII space. The value and sourceSentence stored here use an ordinary ASCII space in that position, so containment must be tested with whitespace runs normalised — it passes that test, and does not pass byte-exact containment.
In conclusion, results suggest a small hypertrophic benefit to employing inter-set rest interval durations >60 s, perhaps mediated by reductions in volume load.
- >90 sseconds of inter-set rest
The rest duration beyond which the analysis DID NOT DETECT appreciable further hypertrophy differences. An absence of detection, not a demonstrated equivalence — it must not be upgraded into 'resting past 90 s provably adds nothing'. NOTE ON WHITESPACE: in the source, the space between '90' and 's' is U+2005 FOUR-PER-EM SPACE, not an ASCII space. The value and sourceSentence stored here use an ordinary ASCII space in that position, so containment must be tested with whitespace runs normalised — it passes that test, and does not pass byte-exact containment.
However, our analysis did not detect appreciable differences in hypertrophy when resting >90 s between sets, consistent with evidence that detrimental effects on volume load tend to plateau beyond this time-frame.
"healthy adults" — the abstract's own wording, from "estimates of pre-/post-study changes in lean/muscle mass in healthy adults". Independently confirmed by string search that the abstract contains no instance of "trained", "untrained", or "participant", so there is no training-status, sex, or age breakdown and no total participant count available from the abstract. No participant n is supplied here rather than inventing or importing one.
Singer A, et al. (2024)Give it a rest: a systematic review with Bayesian meta-analysis on the effect of inter-set rest interval duration on muscle hypertrophy.
Frontiers in sports and active living · PMID 39205815
Meta-analysis · 9 studies, 19 measurements
Who funded itSee the paper's funding and conflict-of-interest statement.
Volume, rep ranges, rest, stretching, sleep — each with its numbers and its limits.
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