High Intensity Interval Training and Heart Health

Older man in spin class

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The number one reason people say they can't stick with an exercise regimen is that they're just too busy. Enter high-intensity interval training, or HIIT for short. A growing body of research is showing that bursts of high-intensity activity can get your heart and lungs just as fit in less time, compared with the traditional prescription of 30 minutes a day of moderate-intensity exercise five days a week.

That sounds great for younger athletes. Many older adults worry that this type of intense exercise will cause more health problems than it solves, by putting their hearts at risk. But research on high-intensity interval training specifically in older adults, including those with age-related illnesses like diabetes and heart disease, is encouraging.

HIIT Basics

High-intensity interval training involves short bouts of intense exercise interspersed with longer periods of slower activity as recovery time. Any aerobic exercise can become a HIIT workout when it incorporates periods of intense effort (like sprinting). Runners may be familiar with Fartlek or "speed play" training, which originated in Scandinavia several decades ago, based on similar principles.

Since then, researchers have tested different interval patterns, varying the intensity and duration of both the all-out and recovery stages.

Martin Gibala, chair of the kinesiology department at McMaster University in Hamilton, Canada, revived interest in interval training in the mid-2000s. His research demonstrated that interval training delivered the same fitness benefits as moderate-intensity exercise in just a fraction of the time. Later, Gibala and his team tested HIIT in eight older adults with diabetes. The study subjects showed measurable, beneficial changes in glucose metabolism, cardiovascular fitness, and body composition after just two weeks (six sessions).

Gibala's data, published in 2011, suggest that high-intensity training can be safe, effective, and—perhaps equally important—time-efficient for adults battling significant health challenges.

"Our study was small, but the results suggest that HIIT has real potential for improving fitness in older adults, without a major time commitment," Gibala said. Indeed, subsequent research by Gibala and others has continued to show the benefits of HIIT for people with diabetes, prediabetes, and other health conditions.

HIIT and the Heart Patient

While numerous studies have shown the benefits of exercise for adults with cardiovascular disease, much of the research has involved moderate-intensity activity. But researchers are now examining whether high-intensity intervals are safe for older adults with serious heart problems. A 2017 study, for example, reviewed research on HIIT in heart patients and found evidence of its safety and efficacy. Other research has shown HIIT to be safe in patients with chronic stroke and in sedentary older men.

Likewise, a review of 10 studies on HIIT in older subjects with conditions ranging from coronary artery disease, heart failure, hypertension, metabolic syndrome, and obesity was published in the British Journal of Sports Medicine in 2014. The meta-analysis revealed that greater improvements in cardiorespiratory fitness were found in these subjects involved in HIIT regimens compared with traditional moderate-intensity exercise programs. Cardiorespiratory fitness—assessed by measuring maximum lung capacity—is also a predictor of better longevity.

Martin Gibala believes HIIT holds real potential and offers a real exercise alternative for improving the health of older adults.

"We know there's much more research to be done on HIIT. The traditional model of exercise may be the 'drug of choice,' with lots of supporting data, but interval training has shown lots of promise," he says. "We're not demonizing traditional cardio guidelines. We just want to say that if people are pressed for time, they can safely consider this different exercise model."

Precautions for Older Adults Getting Started 

The first step is to get a doctor's OK to embark on interval training. Then, ramp up slowly. You don't need to hit a target of 95 percent of your peak heart rate, says Gibala. If your daily exercise consists of an after-dinner walk with your dog, for example, he suggests using landmarks like light posts to insert more intense periods into the activity.

"Just get out of your comfort zone a bit," he advises. "Say, 'for these next two lamp posts I'm going to walk a bit faster.' You get out of breath, then slow down. You get a slight peak and a slight valley. For some people, that's an interval."

Over time—and quite quickly, according to the evidence—your fitness level will improve, you will be able to sustain a higher-intensity effort, and will be able to achieve more of these active intervals.

"We tend to use cycling for interval training because it's easy to measure in the lab," Gibala notes. "But you can also use an elliptical machine, swimming, uphill walking; any approach that uses large muscles like those in the legs will work."

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