Effects of High-Intensity Interval Training Versus Sprint Interval Training on Factors Related to Endurance Performance: A Systematic Review and Meta-Analysis.

Xiao, Y, Li, J, Deng, Z, and Gao, W. Effects of high-intensity interval training versus sprint interval training on factors related to endurance performance: A systematic review and meta-analysis. J Strength Cond Res 40(3): 344-355, 2026-This meta-analysis aimed to compare the long-term effects (≥2 weeks) of high-intensity interval training (HIIT) and sprint interval training (SIT) on endurance performance-related outcomes, including maximal oxygen uptake (V̇o2max), endurance performance, maximal aerobic power/velocity (MAP/MAV), lactate threshold, and running economy. A systematic literature search was conducted using the keywords "high-intensity interval training" and "sprint interval training" in the Web of Science, PubMed, and SPORTDiscus databases. A random-effects model was applied, with standardized mean difference (SMD) calculated for each outcome. Subgroup and regression analyses were performed to examine potential moderating factors. Twelve randomized crossover trials involving 460 subjects were included. High-intensity interval training significantly outperformed SIT in improving V̇o2max (SMD = 0.56, 95% confidence interval [CI]: 0.23-0.88; p < 0.001) and MAP/MAV (SMD = 0.40, 95% CI: 0.06-0.75; p = 0.02). Subgroup analysis revealed that HIIT programs lasting more than 8 weeks were particularly effective for enhancing V̇o2max (SMD = 2.13, p = 0.01), while protocols incorporating work intervals longer than 4 minutes also showed significant benefits (SMD = 1.40, p = 0.03). Furthermore, HIIT resulted in greater improvements in time trial performance compared with SIT in moderately trained individuals. HIIT showed greater improvements in aerobic capacity than SIT, particularly for long-interval protocols (>4 minutes, >8 weeks). Although most outcomes were of low or very low quality (except MAP/MAV), these findings suggest that athletes and coaches may incorporate 3-6 intervals of 4-5 minutes at 80-95% MAV, 2-3 sessions per week, to enhance aerobic capacity.