Subject: How slow should a repetition be? Repetition tempo and hypertrophy
What this means
Barely: faster and slower lifting produced comparable muscle growth, with a trivial difference of 0.09 (95% credible interval −0.04 to 0.22).
B · Reasonable confidence. A solid systematic review with caveats, or consistent indications with a limited scope.
Fourteen studies compared a slower tempo (1.7 to 4.5 seconds per repetition, averaging about 3.5 seconds) with a faster one (0.3 to 2 seconds, averaging about 1 second), holding all other training variables constant. Within-group growth was comparable (faster 0.43, 95% CrI 0.29 to 0.58; slower 0.34, 95% CrI 0.22 to 0.47). The pairwise difference was trivial and slightly favoured the faster tempo (0.09, 95% CrI −0.04 to 0.22), with a low probability that the difference is even small (p = 0.450).
Healthy adults who strength train, in studies where all other training variables were held constant.
Fourteen studies comparing tempos of roughly one second with tempos of roughly 3.5 seconds per repetition.
Differences may still emerge under specific conditions; the certainty of the estimates varied across sub-analyses.
Tempo is not a dial with much hypertrophy behind it. Controlled movement stays in REZA's coaching for other reasons; prescribing a precise tempo is not needed to drive muscle growth.
Systematic review with Bayesian meta-analysis
Subgroup analyses by muscle action (eccentric or concentric), body region (upper or lower) and training to failure produced trivial to small effects, with certainty varying by analysis. The journal issue is dated December 2025; the record was indexed in PubMed on 8 September 2026.
This information is general education about scientific research. It is not personal medical advice and does not replace diagnosis or treatment by a doctor or other healthcare professional. If you have symptoms, a medical condition or take medication, consult your GP or treating professional before changing your training or nutrition.
