Expert Advice
Add intervals of intensity for a stronger heart
When it comes to exercise, interval-training offers the best of both worlds.
When faced with an arduous physical task, most people break up the work with short periods of rest. This pattern of alternating bursts of intense activity with periods of rest, called interval-training, has long been the province of sports trainers and competitive athletes.
Olympic start
Interval training emerged from Central Europe in the late 1940s, the brainchild of athletic trainers looking for ways to give their long-distance runners an edge. It spread to swimmers and other elite athletes. An interval-training plan that involved swimming 50 meters as fast as possible, resting for 10 seconds, and repeating this swim-rest cycle two dozen times before stopping helped the U.S. swim team take 13 of 16 gold medals at the 1964 Olympics in Tokyo. Interval-training is now an integral element of high-level sports.
Why interval-training is special
What makes this exercise regimen so special? For starters, it lets many exercisers spend more time doing a high-intensity activity than they could perform in a single stretch. For example, someone who couldn’t run full speed for five minutes straight might be able to run full speed for 10 minutes by doing it in ten 1-minute intervals and resting in between. Rest breaks give the body time to remove waste products that can make muscles sluggish, tired, or painful.
Working the heart and other muscles hard for brief spurts trains them to use oxygen more efficiently. It conditions them to work through brief periods when the demand for oxygen temporarily outstrips the supply. It helps the body create new muscle fibers. A handful of studies show that interval-training also changes mitochondria, the tiny powerhouses that provide energy to cells so they burn fat more efficiently.
Intense activity, even brief spurts of it, is better than moderate activity at turning on genes that promote the growth of new blood vessels, make blood vessels more flexible, intensify the body‘s defenses against harmful antioxidants, and ease low-level inflammation.
All these changes have a tangible result: the ability to be more active. They also quietly guard against invisible forces that erode cardiovascular health — forces such as the entry of cholesterol into artery walls, the stiffening of arteries, or the accumulation of fat.
Design your own
Outside of competitive sports, interval-training isn’t a rigorously defined regimen. There is no single formula for how long and how hard to exercise or how long and how often to rest. You can try Fartlek, a Swedish word that means speed play — you set the intervals based on how you feel on a particular day. Or you can set up a more scientific approach with help from a personal trainer or fitness expert. The main guidelines to apply are these:
- The high-intensity bursts should last long enough and be strenuous enough that you are out of breath. If you monitor your heart rate, it should be more than 80% of your maximum heart rate.
- Rest periods should be long enough that you are ready to go again, but they should not be so long that your heart slows to its resting rate.
- Warm up before exercising, and cool down afterward.
- Don’t do interval-training on consecutive days. Let your muscles recuperate in between. Two or three times a week is plenty.
Interval-training is most easily done on a treadmill, where you can tinker with the speed of the machine. But you can also do it anywhere you exercise — around the neighborhood, in a pool, on a bike, or cross-country skiing.
If you are a runner, bust out into a sprint now and then. If you swim, alternate fast and slow laps. If you bike, sprinkle your ride with a few Tour de France finishes.
A warning is in order. Interval training isn’t for everyone. Revving the heart rate way up could provoke cardiac arrest or other disasters in people at risk for them. So if you have heart disease, high blood pressure, or other risk factors, check with your doctor before starting interval training.
