Background: Sprint interval training (SIT) involving repeated 30-s "all out" efforts have resulted in significantly improved skeletal muscle oxidative capacity, maximal oxygen uptake, and endurance performance. The positive impact of SIT on cardiorespiratory fitness has far-reaching health implications.
Objective: The objective of this study was to perform a systematic review of the literature and meta-analysis to determine the effects of SIT on aerobic capacity.
Methods: A search of the literature was conducted using the key words 'sprint interval training', 'high intensity intermittent training/exercise', 'aerobic capacity', and 'maximal oxygen uptake'. Seventeen effects were analyzed from 16 randomized controlled trials of 318 participants. The mean ± standard deviation number of participants was 18.7 ± 5.1. Participant age was 23.5 ± 4.3 years.
Results: The effect size calculated for all studies indicates that supramaximal-intensity SIT has a small-to-moderate effect (Cohen's d = 0.32, 95 % CI 0.10-0.55; z = 2.79, P < 0.01) on aerobic capacity with an aggregate improvement of ~3.6 mL·kg⁻¹·min⁻¹ (~8 % increase). The effect is moderate to large in comparison with no-exercise control groups (Cohen's d = 0.69, 95 % CI 0.46-0.93; z = 5.84, P < 0.01) and not different when compared with endurance training control groups (Cohen's d = 0.04, 95 % CI -0.17 to 0.24; z = 0.36, P = 0.72).
Conclusion: SIT improves aerobic capacity in healthy, young people. Relative to continuous endurance training of moderate intensity, SIT presents an equally effective alternative with a reduced volume of activity. This evaluation of effects and analysis of moderating variables consolidates the findings of small-sample studies and contributes to the practical application of SIT to improve cardiorespiratory fitness and health.