Figure 3. The effect of varying the intensity of interval training on changes in 40 km time-trial performance.

Well-trained male cyclists were randomly assigned to one of five different doses of high-intensity interval training (HIT): 12 × 30 s at 175% of peak sustained power output (PPO), 12 × 1 min s at 100% PPO, 12 × 2 min at 90% PPO, 8 × 4 min at 85% PPO, or 4 × 8 min at 80% PPO. Cyclists completed six HIT sessions over a 3 week period in addition to their habitual aerobic base training. Redrawn from Stepto et al. (1999) with permission.