Government guidelines recommend that each week we do at least 150 to 300 minutes of moderate-intensity aerobic exercises like brisk walking or fast dancing, or 75 minutes of vigorous-intensity aerobic exercises like running or hiking uphill. The former requires a considerable time investment, while the latter involves an intensity level not everyone can handle, which may be why only one in five people follow either recommendation.
Research suggests that a shortcut method called high-intensity interval training (HIIT) offers similar health benefits in less time than moderate-intensity exercise. And, it’s achievable for healthy older adults and modifiable for people with health conditions like heart disease and chronic obstructive pulmonary disease (COPD).
Moderate vs. high intensity
When you work out at moderate intensity, your exertion level should feel light to somewhat hard. Examples of moderate-intensity exercises include brisk walking and biking slower than 10 miles per hour.
In HIIT, you work out at a very hard intensity for short bouts ranging from 30 seconds to 3 minutes to increase your heart rate. You alternate those high-energy bursts with moderate exercise or rest for the same amount of time or longer so your body can partially recover. You can also monitor your heart rate to see how intensely you’re working. With HIIT, you exercise at 70 percent or higher of your maximum heart rate during the high-intensity portion.
The simplest way to compute your approximate target heart rate is to subtract your age from 220—that’s your maximum heart rate—and then calculate 60 and 80 percent of that number. For example, if you are 50, your maximum heart rate is 220 minus 50, or 170. Then multiply 170 by 0.6 (for the low end) and by 0.8 (for the high end), which gives a range of 102 to 136.
The rest periods in HIIT allow you to tolerate more intense bouts of exercise. That may be why people stick with this program, and studies suggest they enjoy it more than moderate-intensity training. Plus, HIIT doesn’t require a gym membership—or any equipment at all. Simply walking fast or jogging in place is enough to boost your heart rate into the target zone.
HIIT for any age and level
One advantage of HIIT is that you work out for only about 30 minutes to achieve similar results from an hour-long moderate-intensity workout. In HIIT, you work at close to your maximum heart rate. That increases oxygen uptake by your muscles, which helps you burn more calories and improves your cardiorespiratory (heart and lung) fitness—a marker of your overall health. HIIT also improves muscle strength and helps reduce body mass index (BMI).
Most HIIT research has involved fit young people. But some studies suggest that HIIT can be safe and beneficial for older people even with health conditions. For example, a Japanese study, published in Mayo Clinic Proceedings in December 2019, looked at the effects of HIIT in nearly 700 middle-aged and older adults (average age, 65), some of whom had high blood pressure, high cholesterol, and diabetes. Participants alternated three minutes of slow walking with three minutes of fast walking for 30 minutes or more, four or more days a week. After five months, participants improved their peak exercise capacity and walking speed, along with health measures like blood sugar, BMI, and cholesterol.
Other evidence suggests that HIIT can boost brainpower. A study in the October 2019 issue of Applied Physiology, Nutrition, and Metabolism found that three weekly sessions of treadmill HIIT workouts over three months by previously sedentary adults over age 60 led to memory improvements compared with moderate-intensity exercise.
Some studies recommend HIIT for people with COPD. Individuals with COPD often can’t work out for long durations because symptoms such as shortness of breath prevent them from doing so. HIIT’s intervals with rest periods make it easier for them to sustain than continuous exercise at moderate intensity—in half the time—while still improving shortness of breath and exercise tolerance.
As with any new vigorous exercise program, consult your doctor before trying HIIT if you have been sedentary or have a medical condition or previous injury that limits your ability to exercise. If you have arthritis, you can perform HIIT in the water to reduce pressure on your joints.
You can adapt HIIT to your preferred mode of exercise like walking, riding a stationary bike, or running outdoors or on a treadmill. Start with three or four intervals and gradually work up to eight or 10 for at least 30 minutes when you’re ready. For example, if you’re riding a stationary bike, pedal as fast as you can for 30 seconds or until you feel too exhausted to continue. Then, cut back to very gentle pedaling for a minute, followed by another all-out 30-second sprint. Repeat as you can. Do this for several minutes several times a week. You can also try to work up to one- or two-minute sprints, repeated 10 times.
If the workout is too intense for you, try modifying it by reducing the high-intensity portion to 10 or 20 seconds with a recovery interval of at least twice as long.
HIIT puts a lot of stress on your body that could lead to injury, so you don’t want to do more than two or three sessions each week. Give yourself at least 48 hours in between each HIIT workout for your muscles to recover. On your off days, do a low- or moderate-intensity activity.
This article first appeared in the April 2020 issue of UC Berkeley Health After 50.
Also see Do 7-Minute Workouts Work?