High-intensity interval training increases fat burning better than slow and steady cardio. But is slow and steady cardio better for improving cardiovascular fitness and health? Japanese researchers had athletes follow a 15-week cardio program. One group exercised continuously on a stationary cycle for 20–25 minutes at about 75% of their max heart rate, three days per week. The second group performed HIIT—10 cycles of 10-second all-out sprints with 20-second rest periods, for a total of five minutes (just one minute and 40 seconds of total exercise time), three times per week. Both groups increased their max oxygen consumption (VO2 max—a measure of cardiovascular fitness) to the same degree despite the fact that the HIIT group exercised for less time.