Interval training consists of alternating between low- and high-intensity cardiovascular activity. It is designed to increase endurance and overall fitness. As workout intensities vary from person to person, there are no hard and fast rules that define low or high intensity. Instead, heart rate is often used to determine intensity level. Achieving a target heart rate indicates a high-intensity interval, while heart rates below this level represent low-intensity intervals.
According to the American Heart Association, the target heart rate range is 50 to 85 percent of your heart's maximum rate, and this is the ideal level at which to work out. Calculate your maximum heart rate per minute by subtracting your age from 220.
Most cardiovascular machines, like stationary bicycles and treadmills, have heart rate monitors installed. However, if this is not an option, individual heart rate monitors can be purchased at most sporting goods stores. Additionally, you can calculate your heart rate per minute by taking your pulse for six seconds and multiplying that number by 10.
Intervals can be used with any cardiovascular workout, including running, walking, bicycling, stair-stepping or using an elliptical machine. Incorporate intervals into your workouts depending on your fitness level. When starting out with interval training, high-intensity intervals should last from 30 seconds to two minutes with a heart rate in the lower target heart zone, approximately 50 to 65 percent of the maximum heart rate. Low-intensity intervals should last approximately two to five minutes, allowing the heart rate to drop just below the target heart rate zone.
As strength and endurance increases, high-intensity intervals should last two to five minutes with a heart rate of 80 to 85 percent of the maximum heart rate. Low-intensity intervals decrease to one to two minutes at a time, with the heart rate dropping to 50 to 65 percent of the maximum heart rate.
Interval training incorporates both the aerobic and anaerobic systems of the body. The aerobic system is responsible for the body's ability to maintain physical activity for an extended amount of time. The anaerobic system, on the other hand, provides the energy for short bursts of exertion or activity.
As interval training incorporates high-intensity cardiovascular exercise, it helps to burn more calories during the workout. The mix of aerobic and anaerobic activity helps to increase endurance and stamina. In addition, this mix helps to prevent muscle soreness that frequently comes with extended periods of high-intensity activity. Adjusting the intervals to match target heart rates helps to improve the heart's efficiency while also increasing blood and oxygen flow to the entire body.
As with all workout regimes, interval training involves a certain degree of risk from injury or overexertion. High-intensity intervals may not be appropriate for individuals with chronic health problems or heart conditions. Inexperienced exercisers may experience injuries or muscle soreness if the initial interval training program is too intense. Consult your physician prior to starting any exercise program.
- American Heart Association: Target Heart Rate
- The Complete Book of Personal Training; Douglas Brooks; 2004
- American Council on Exercise: Interval Training
- American Council on Exercise: High Intensity Interval Training
- BananaStock/BananaStock/Getty Images
This article reflects the views of the writer and does not necessarily reflect the views of Jillian Michaels or JillianMichaels.com.