High-intensity interval training combines short spurts of very high-intensity aerobic exercise with more extended periods of low-intensity exercise. High-intensity interval training sessions are popular because they train the body to become efficient at using energy.
For an exercise to be considered highly intense, it should be a seven or greater on a scale from one to 10, according to Ace Fitness. This usually means raising the heart rate over 80 percent. During a high-intensity interval training workout, the high-intensity exercise session should last at least 30 seconds but can last as long as 2 minutes. High-intensity sessions are followed by 2 to 3 minutes of lower-intensity sessions, commonly referred to as active recovery. High-intensity interval training workouts alternate between high and low sessions, consisting of about 10 to 12 sessions total. High-intensity exercises can include anything that raises the heart rate, such as sprinting, cycling, stair climbing, and using treadmills and stationary bikes. During the low-intensity session of the workout, simply slowing down the high-intensity exercise suffices. Because high-intensity interval training sessions can be physically trying, most experts agree that keeping them within 20 minutes is healthy and beneficial, reports Prevention Magazine. Additionally, it is best to limit sessions to no more than twice a week, which allows the body to recover.