High-intensity interval training, also known as HIIT, is a form of interval training which involves short intervals of maximum intensity cardio interspersed with longer intervals of low to moderate-intensity cardio. What makes high-intensity interval training different than regular interval training is that the maximum-intensity intervals are based on maximum effort not a specific heart rate. Any type of cardio exercise can be used for an HIIT workout including running, swimming, walking, jumping rope or the use of equipment such as a treadmill, elliptical or stair-stepper.
Benefits of High-Intensity Interval Training
One reason high-intensity interval training is so popular is because a HIIT workout takes very little time. A typical HIIT workout is 15 to 20 minutes in duration, depending on one's fitness levels.
Research suggests that short, intense cardio intervals burn more body fat than sustained activity, such as steady-state cardio. During traditional cardio workouts, calories are burned only while performing the workout whereas high-intensity interval training can boost metabolism for up to 24 hours after a workout.
Doing HIIT workouts help the body retain muscle mass during weight loss as opposed to traditional cardio where muscles can start to break down after 40 minutes into a moderate-intensity cardio workout.
Since glycogen stores are low after a strength training workout, when HIIT is performed after strength training, the body has to turn to excess fat stores to provide the body energy to complete the HIIT workout.
Example HIIT Workout
HIIT workouts vary among individuals depending on fitness level, but an example of an HIIT workout would be:
- 5-minute warm-up at a slow, easy pace
- 30-second maximum-intensity interval
- 90-second low to moderate-intensity interval
- Repeat 6 to 7 times
- 5-minute cool down
As the body becomes stronger and adapts to a specific high-intensity interval training workout, the intervals can be prolonged with a maximum-intensity interval of 1 minute and low to moderate-intensity intervals up to 4 minutes. Because of the intensity level, HIIT workouts are usually performed only 2 to 3 times per week.
Disadvantages of High-Intensity Interval Training
High-intensity interval training workouts are not for everyone as the maximum-intensity intervals are grueling. Those who are out of shape or have a heart condition should not perform high-intensity interval training workouts. Also, even for those who are in good physical shape, overtraining can occur if HIIT is performed too often. Anyone considering high-intensity interval training should consult a physician before incorporating HIIT into their workout regimen.
References:
Helgerud, et al., (2007). Aerobic high-intensity intervals improve VO2max more than moderate training, Medicine & Science in Sports & Exercise, 39 (4), 665-671.
Irving, et al., (2008). Effect of exercise training intensity on abdominal visceral fat and body composition, Medicine & Science in Sports & Exercise, 40 (11), 1863-1872.
Walker, R. (2009, Sep/Oct). Super intervals. Hers Muscle & Fitness, 48-54.
Jennifer Murray - Jennifer Murray is a freelance writer specializing in nutrition, weight loss and fitness.
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