The effects of sprint interval training on physical performance: a systematic review and meta-analysis.

The present study aimed to synthesise findings from published research and through meta-analysis quantify the effect of sprint interval training (SIT) and potential moderators on physical performance outcomes (categorised as aerobic; anaerobic; mixed aerobic/anaerobic; or muscular force) with healthy adults, in addition to assessing the methodological quality of included studies and the existence of small study effects. Fifty-five studies were included (50% moderate methodological quality, 42% low methodological quality), with 58% comprising an intervention duration of ≤4 weeks and an array of different training protocols. Bayesian meta-analysis of standardized mean differences (SMD) identified a medium effect of improved physical performance with SIT (ES0.5 = 0.52 [95%CrI: 0.42 to 0.62]). Moderator analyses identified overlap between outcome types with the largest effects estimated for anaerobic outcomes (ES0.5 = 0.61 [95%CrI: 0.48 to 0.75]). Moderator effects were identified for intervention duration, sprint length, and number of sprints performed per session, with larger effects obtained for greater values of each moderator. A substantive number of very large effect sizes (41 SMDs >2) were identified with additional evidence of extensive small study effects. This meta-analysis demonstrates that short-term SIT interventions are effective for developing moderate improvements in physical performance outcomes. However, extensive small study effects, likely influenced by researchers analysing many outcomes, suggests potential overestimation of reported effects. Future research should analyse fewer a priori selected outcomes and investigate models to progress SIT interventions for longer-term performance improvements