Author(s): HUTCHINSON, M., VOLLAARD, N., PAVAL, R., GALLAGHER, I.J., Institution: UNIVERSITY OF STIRLING, Country: UNITED KINGDOM, Abstract-ID: 2433

INTRODUCTION:
The most commonly used sprint interval training (SIT) protocol within research focusing on improving VO2max involves 4-6x30-s repeated “all-out” sprints performed 3 times per week. The finding that reducing the volume of sprint exercise to 2x20-s sprints does not attenuate health improvements [1] led to increased interest in SIT protocols involving fewer / shorter sprints. A previous meta-analysis analysed 34 SIT studies (n=418 participants) and concluded that improvements in VO2max are not attenuated with fewer sprint repetitions [2]. However, the use of magnitude-based inference and the relatively low number of studies using <6 sprint repetitions were limitations of this study, providing a justification for the need for an updated meta-analysis using more robust statistical methods. The aim of this study was to investigate the effect of the number of sprint repetitions on changes in VO2max in SIT exercise protocols involving untrained participants.
METHODS:
The study (PROSPERO ID: CRD42022349104) was carried out in accordance with the guidelines of Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). Online databases Web of Science and PubMed were searched up to August 2022 for the independent variable search terms “Wingate”, “all-out”, “sprint” and “interval training” combined with dependent variable search terms “fitness”, “aerobic capacity”, “aerobic power”, “VO2max”, “VO2peak”, “oxygen uptake” and “oxygen consumption”. Studies included in the previous review [2] were added. A Bayesian meta-analysis was performed to examine the effect of the number of sprints per training session on changes in VO2max with training, along with moderating effects of age, BMI, baseline VO2max, total sprint volume per week, intervention duration in weeks, and work/rest ratio. Means and effect size with high-density intervals (HDIs) were used to describe the results.
RESULTS:
A total of 67 studies involving 79 trials (n=1013 participants) were included in the analysis. Overall, SIT interventions were associated with improved VO2max (Mean = 8.7%, 95% HDI: 6.8% to 10.5%). There was no meaningful relationship between the magnitude of the change in VO2max and the number of sprints per session (ES=-0.01, 95% HDI: -0.13 to 0.12). There was a small moderating effect of age (ES=-0.03, 95% HDI: -0.05 to -0.01), but not for other moderators.
CONCLUSION:
With increased statistical power and a more robust statistical analysis approach, the present updated meta-analysis confirmed the previous finding that performing a greater number of sprint repetitions in a SIT session does not result in greater improvements in VO2max. Considering the target audience of insufficiently active individuals and the proclaimed benefit of time-efficiency, research into the health benefits of SIT should focus on protocols involving a low number (2-3) of sprints.