High-intensity interval training (HIIT) has been touted as a mode of exercise that can improve health and fat loss in a fraction of the time of typical moderate-intensity workouts. But does HIIT really live up to the hype?
HIIT is defined by exercising at or very near your maximal exercise capacity for short bursts of time, spaced by low-to-moderate intensity exercise. In practice, this could mean sprinting at full speed for 60 seconds, then walking or jogging for 30-60 seconds. Intervals are repeated 5 to 10 times, for a total session of 10 to 20 minutes. Any form of aerobic activity can be done in high-intensity intervals, including cycling, swimming, and rowing.
Traditional recommendations for physical fitness have taken a different approach, emphasizing moderate aerobic activity for at least 30 minutes, three to five days a week. Recent studies, however, have shown that higher intensity exercise can be equally, if not more effective for improving health and aiding fat loss. Moreover, the workouts can be done in just a few short sessions per week. High-intensity sessions also appear to make lower intensity exercise sessions much easier.
For health, HIIT has been shown to improve markers of cardiovascular disease by reducing fasting glucose, improving insulin sensitivity, increasing aerobic fitness, raising (“good”) HDL cholesterol, lowering blood pressure and decreasing body fat.
HIIT has also been demonstrated to improve fitness in children and can significantly improve performance in highly trained endurance athletes. However, despite the clear advantage of using HIIT in training, some scientists have warned against relying on it exclusively since high-volume, lower intensity workouts may also offer unique advantages.
The biggest challenge for incorporating HIIT into your fitness regimen is deciphering exactly how much exercise is safe and effective for different individuals. Some labs have suggested alternative programs for individuals with compromised health, though these have been challenged as well. That said, most HIIT models tested have proven both safe and effective.
In summary, HIIT is potentially more effective than traditional aerobic exercise programs in improving fitness and is particularly valuable for people who don’t have much time to invest in working out. However, there is still no consensus on the ideal training program for specific individuals.
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Image: Home Stretch, a Creative Commons Attribution (2.0) image from Drongowski’s photostream.