Background: Sprint interval training (SIT) improves maximal aerobic and anaerobic performance, including oxygen uptake (VO2<inf>max</inf>), power output, and sprint performance. This study aimed to investigate the effect of SIT load on V̇O<inf>2max</inf> in trained subjects.
Methods: SIT was performed twice a week for three weeks by twenty-four trained men (aged: 20.7±2.7, V̇O<inf>2max</inf> 43.6±6.5) and consisted of seven bouts of 10-s cycling sprints followed by a 4-min rest. Subjects were divided into two groups depending on the relative resistance of the load compared to their body mass (BM): 7.5% (S7.5) and 10% (S10). We measured the peak power, mean power, and peak cadence in SIT during the first and final sessions. V̇O<inf>2max</inf>, maximum aerobic power (MAP), heart rate, and lactate (La) concentration were measured before and after SIT using incremental tests.
Results: After 3 weeks of SIT, V̇O<inf>2max</inf>, MAP, and La improved significantly in both S7.5 and S10 groups. In addition, changes in V̇O<inf>2max</inf> in S10 were higher than those in S7.5 (2.2±11.2% vs. 9.23±9.57%, P=0.029, adjusted by pre V̇O<inf>2max</inf>). MAP measurements showed the same results (2.2±11.3% vs. 8.3±10.0%, P=0.015, adjusted by pre-MAP). However, there was no significant interaction between time and group. A significant increase in peak cadence from first session to sixth sessions was observed in S7.5 (P=0.01, ES = 0.93, 95% confidence interval [CI]: 0.02-1.78) but not in S10 (P=0.132, ES = 0.22, 95% [CI]: -0.59-1.01).
Conclusions: Our results suggest that 3 weeks of SIT improves endurance performance in trained subjects. It seems that SIT at 10% load may tend to be more effective.