Hall, Andy J.; Aspe, Rodrigo R.; Craig, Thomas P.; Kavaliauskas, Mykolas; Babraj, John; Swinton, Paul A.1

Journal of Strength and Conditioning Research 37(2):p 457-481, February 2023. | DOI: 10.1519/JSC.0000000000004257

PURPOSE:

1. To combine findings from published research and through meta-analysis quantify the effect of sprint interval training (SIT) and potential moderators on physical performance outcomes (categorized as aerobic, anaerobic, mixed aerobic-anaerobic, or muscular force) with healthy adults.

2. To assess the methodological quality of included studies and the existence of small study effects.

PROCEDURES:

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.

CONCLUSIONS:

Bayesian’s meta-analysis of standardized mean differences (SMD) identified a medium effect of improved physical performance with SIT (ES0.5 = 0.52; 95% credible intervals [CrI]: 0.42–0.62).

Moderator analyses identified overlap between outcome types with the largest effects estimated for anaerobic outcomes (ES0.5 = 0.61; 95% CrI: 0.48–0.75).

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 analyzing many outcomes, suggest potential overestimation of reported effects. Future research should analyze fewer a priori-selected outcomes and investigate models to progress SIT interventions for longer-term performance improvements.

IN PLAIN ENGLISH:

Because improved sprint speed is largely determined by genetic potential – and the fact that it is difficult to improve speed via significant changes beyond one’s physical formative years (i.e., teach proper running form at a young age and hone and refine those skills as physical maturity progresses) – don’t expect significant improvements, especially in adults studied here.