Rest interval duration is an important, yet sometimes overlooked, variable in exercise prescription that affects both acute performance and physiological responses. Traditional prescriptions typically use fixed rest intervals (for example 1–3 minutes), which may not account for inter- and intra-individual variability in recovery. An alternative approach is self-selected rest intervals, in which trainees autonomously determine recovery time based on their perceived readiness. Prior primary studies have reported mixed findings: some suggest performance benefits when participants choose longer rests, while others raise concerns about perceptual bias or insufficient recovery when trainees shorten rest to maintain pace. Because most primary trials are small and heterogeneous, the authors performed a systematic review and meta-analysis to synthesize available randomized crossover evidence on the acute effects of self-selected versus fixed rest intervals on exercise performance, heart rate, and blood lactate.
The review followed PRISMA guidance for three-level meta-analysis and registered a protocol on PROSPERO (CRD420261334983). A systematic search of Web of Science, PubMed, Cochrane Library, and Embase covered database inception through March 20, 2026. Search terms combined variants of self-selected or self-regulated rest with randomized trial terminology. Reference lists of included papers were screened to identify additional studies.
Selection followed the PICOS framework. Included studies were acute randomized controlled trials (mostly randomized crossover designs) enrolling participants with at least one year of training experience, comparing self-selected rest intervals to fixed rest intervals, and reporting at least one performance or physiological outcome (for example repetitions, average power, speed, lactate, or heart rate). Exclusions included non-original research, duplicate reports, unavailable full text, or incomplete data. Two reviewers independently screened records and extracted data; disagreements were resolved by additional investigators. When quantitative results were presented graphically, WebPlotDigitizer was used to retrieve values. Conversions from reported CIs or standard errors to standard deviations were performed using standard formulas when required.
Risk of bias was assessed independently by two reviewers using the Cochrane Risk of Bias 2 tool across domains including randomization, deviations from assigned interventions, missing outcomes, measurement, and reporting. For meta-analysis, the authors used a three-level random-effects model to account for dependence among multiple effect sizes reported within studies. This approach partitions variance into sampling variance (level 1), within-study variance (level 2), and between-study variance (level 3). Subgroup analyses, meta-regression, and sensitivity analyses were conducted to explore moderators and robustness.
Sixteen studies (k = 16) totaling 281 participants met inclusion criteria and were analyzed. Included trials varied in training tasks, participant characteristics, and outcome measures. The manuscript provides figures and supplemental appendices detailing search strategy, included study characteristics, and extracted data.
The pooled effect for exercise performance comparing self-selected with fixed rest intervals did not reach statistical significance in the primary analysis (Hedges’ g = 0.27, 95% CI [−0.14, 0.69], p = 0.29). Considerable between-study heterogeneity was noted. In sensitivity analyses, removal of outlier studies yielded a small but statistically significant effect favoring self-selected rest intervals (g = 0.20, 95% CI [0.08, 0.33], p < 0.01), indicating that conclusions about performance depend on inclusion of influential studies.
For physiological responses, pooled effects showed no meaningful differences between self-selected and fixed rest strategies. Heart rate showed essentially no effect (g = 0.002, p = 0.98). Blood lactate also did not differ significantly between conditions (g = −0.20, p = 0.36).
The authors conducted subgroup analyses and meta-regressions to explore potential moderators of the primary outcomes and performed sensitivity checks to assess robustness. The reported small performance advantage with self-selection was sensitive to outlier removal, and overall heterogeneity limited the strength of directional conclusions. Full subgroup and regression results are presented in the paper and supporting information.
The aggregated evidence indicates that, across the included acute randomized trials, self-selected rest intervals and fixed rest intervals produce broadly comparable acute effects on performance and on common physiological markers such as heart rate and blood lactate. A modest performance advantage for self-selection emerged only after excluding outlying studies, suggesting any real benefit is likely small and context-dependent. The authors highlight several considerations: primary studies were often small and used varied protocols, which contributed to heterogeneity; perceptual strategies for selecting rest may be biased or influenced by task demands; and the clinical or practical relevance of a small standardized effect size requires careful interpretation in applied training contexts.
Limitations noted by the authors include the small sample sizes of many included trials, heterogeneous training tasks and outcome measures, and sensitivity of pooled effects to outliers. Risk-of-bias assessments were performed, but variability among studies in methodology and reporting reduces certainty. The authors caution that conclusions should be interpreted in light of these limitations.
In this synthesis of 16 acute randomized trials (281 participants), self-selected and fixed rest interval strategies produced comparable acute effects on exercise performance, heart rate, and blood lactate. A small performance benefit favoring self-selection emerged in sensitivity analyses after outlier removal, but overall findings are tempered by heterogeneity and sensitivity to influential studies. Trainers and researchers should interpret these results cautiously and consider individual and task-specific factors when choosing rest strategies. Further larger and more standardized trials are needed to clarify circumstances under which self-selected rest intervals may meaningfully improve performance.