Physical activity is integral to good health. High-intensity interval training, or HIIT, is more time-efficient than traditional workouts, and research has shown it has many health benefits, including improving fitness, cardiovascular health, and insulin function, and helping with weight loss.
What is HIIT? HIIT involves performing short, vigorous bursts of activity followed by low-intensity activity or rest. This cycle is repeated for a series of sets. The high-intensity activity should get one’s heart rate up to about 70 to 90 percent of maximum. For the low-intensity period, heart rate should be about 60 to 65 percent of maximum. (A quick estimate of your maximum heart rate is 220 minus your age.) On a stationary bike, for example, a HIIT workout could be 30 seconds of pedaling at maximum effort followed by two to three minutes of easy pedaling, repeated for three to five cycles. Activities and intervals can be adapted to an individual’s current fitness level. Any activity that gets one’s heart rate up, including walking/jogging, using an exercise machine, or performing jumping jacks, sit-ups, push-ups, or squats will work.
The standard physical activity recommendation of 150 minutes of moderate activity or 75 minutes of vigorous activity weekly for good health still stands. HIIT is a type of vigorous activity that has been recognized as a more efficient alternative to traditional moderate-intensity continuous training. With a physician’s approval, HIIT can be an option for all ages and fitness levels, including individuals who are currently sedentary, unfit, or living with a lifestyle-related disease like diabetes or high blood pressure.
The Research. Research shows that engaging in HIIT is an efficient way to achieve health benefits, including weight loss. In one study, overweight and obese participants reduced body fat and waist circumference with both traditional and HIIT workouts in 10 weeks, but those who did HIIT spent 90 minutes per week working out compared to two and a half hours of traditional activity.
HIIT may be good for the brain, too. In a study published in Applied Physiology, Nutrition and Metabolism in 2019, healthy but sedentary adults between the ages of 60 and 88 who completed three HIIT workouts per week for 12 weeks improved memory performance up to 30 percent, while participants who worked out moderately saw no improvement on average.
High-intensity training may help maintain healthy blood-sugar levels and increase glucose metabolism and insulin sensitivity in both healthy individuals and those with prediabetes and diabetes. In one study, for example, glucose metabolism and insulin sensitivity of insulin-resistant participants were raised to match the levels of healthy participants after two weeks of HIIT training.
Exercise Caution. Vigorous physical activity can put people with heart conditions and those who are not regularly active at greater risk of cardiovascular events, according to a recent statement by the American Heart Association. HIIT is an intense workout and should be approached cautiously and progressively: starting slowly and building over time. For those who have not been physically active or who have underlying medical conditions, it’s important to discuss the benefits and risks of any new physical activity program with a physician before beginning.
Give HIIT a Try. Keep in mind that “high intensity” is a relative term that can mean something very different for everyone. With proper precautions, HIIT can be adapted to meet the needs of a variety of fitness levels, ages, and physical limitations. That’s because you choose each variable: the activity (or activities), the length of work and rest, and the duration of the workout.
Always warm up and stretch before starting. It is best to do HIIT while wearing a heart rate monitor (such as those found on fitness tracking bands). If you don’t own a heart rate monitor, you’ll know you’re working hard enough if it becomes difficult to speak during the short high intensity phase. Be sure to let your heart rate drop and your breathing ease before beginning another high-intensity phase. Most importantly, choose activities you enjoy and change them up as necessary to keep yourself interested.