It’s well known that high-intensity interval training (HIIT), which typically involves alternating between brief periods of extremely high-intensity cardiorespiratory activity and longer bouts of lower-intensity exercise, can deliver many benefits to adults, including increased caloric expenditure, improved aerobic efficiency, elevated aerobic capacity and increased lean muscle mass. However, as a health and exercise professional, you may be unsure if the physically demanding work intervals of HIIT are appropriate for older adults. More specifically, can HIIT be tolerated by individuals over the age of 50 and is it an advisable mode of exercise for adults in the later years of the human life span?

This article examines the researched benefits of HIIT for this population, as well as the safety concerns and best practices of incorporating HIIT workouts into the training programs of active older adult clients. 

The Benefits of Lifelong Exercise 

In the late 1960s and early 1970s, a number of factors—a rise in the popularity of running and jogging, the emergence of dance exercise and the increased visibility of bodybuilding, to name a few—combined to make exercise a popular recreational pastime. These were the early days of the modern fitness era, when making time for exercise became a fundamental part of many lives. That context is important because the adults who first started exercising during this time have been exposed to or even participated regularly in physical activity for most of their adult lives. Now in their 60s, 70s or beyond, these lifelong exercisers are more likely to have the physical ability to participate in high-intensity workouts. 

For example, one study of lifelong exercisers in their 70s found that these individuals had extensive capillary density in muscle tissue, along with the enzymes required for efficient energy metabolization. The study focused on three groups of older adults: one group that had participated in casual but consistent exercise throughout their lives (about 50 years of adulthood); one group that regularly trained for competitive running events since the 1970s; and one group that was not physically active. In addition, the study included a group of younger adults in their 20s so researchers could compare tissue samples between the two age groups. Both groups of active older adults exercised an average of four days a week, which provides powerful evidence that maintaining a high level of fitness can help muscle tissue function as if it were years younger. Researchers observed that the active older adults had tissue samples that were similar to those of the younger adults, noting, “Fifty years of lifelong exercise fully preserved skeletal muscle capillarization and aerobic enzymes.” This increased oxygen consumption and substrate metabolism improved the ability of muscle to function and interact with other tissues. 

This evidence suggests that older adults who have maintained their fitness throughout their lives may certainly have the physiological capability of performing high-intensity exercise.

HIIT For Chronic Health Conditions 

So, it’s one thing to put a fit, lifelong exerciser through an intense interval workout, but what about clients who may just be starting their fitness journeys or are returning after not being active for a period of time? Or what about those who are dealing with a chronic health condition—is HIIT appropriate for these individuals, too? While it may seem that HIIT is too physically demanding for older individuals or those living with chronic health conditions, an extensive body of research suggests that HIIT is not only appropriate for these individuals, it may even be able to provide more benefits than other, less-intense modes of exercise. In fact, research suggests that HIIT could provide benefits for exercise enthusiasts regardless of age or chronic health conditions. Let’s take a closer look at that research…

Hypertension, or high blood pressure, is a common risk factor for developing further cardiovascular disease that could result in an early death. As arterial stiffness increases, it is more challenging for the heart to perform its function of pumping blood around the body. It is widely accepted that low- to moderate-intensity cardiorespiratory exercise can help improve aerobic capacity and reduce numerous risk factors, including hypertension, that could lead to heart disease. It’s important to note, however, that evidence is accumulating that HIIT may not only be safe for people at risk of heart disease, it may also be a more effective option when compared to lower-intensity exercise. In a review of the literature comparing HIIT to continuous moderate-intensity exercise, Emmanuel Ciolac, PhD, of São Paulo State University, observed that the former is “superior” to the latter for improving cardiorespiratory fitness and improving numerous health markers that lower the risks for developing hypertension and other forms of cardiorespiratory disease. 

Additional research suggests that individuals who have experienced heart attacks or gone through heart surgery may benefit from HIIT as a component of cardiac rehabilitation. In fact, a variety of studies have found that shorter, more intense workouts with HIIT may provide more favorable outcomes for heart patients when compared to moderate-intensity, steady-state exercise. A review of the literature, for example, revealed that interval workouts put less stress on the heart when compared to steady-state aerobic exercise, and the risk of a cardiac event is low for cardiac rehab patients whether participants participate in moderate-intensity or HIIT workouts in a supervised setting. Additionally, researchers of a randomized controlled study concluded that “high-intensity aerobic exercise is superior compared to moderate-intensity exercise for increasing cardiorespiratory fitness in stable coronary artery disease patients.” 

There also is good news for individuals dealing with coronary artery disease (CAD). A recent meta-analysis compared the benefits of HIIT to moderate-intensity continuous training (MICT) for individuals with CAD. The study authors surveyed 12 studies on the topic and concluded that “HIIT is a safe and simple intervention that could potentially be beneficial for patients with coronary artery disease.”

Although research in this area has predominantly focused on men, this study included a group of recreationally active women between the ages of 40 and 64 years. The purpose of the 12-week investigation was to determine how sprint interval training would affect the aerobic capacity of the women involved in the study and whether women who were casual exercise participants could benefit from high-intensity exercise. To that end, they measured the effects of a concurrent exercise program that included resistance training with 40-second sprint intervals at 95% of age-predicted maximal heart rate. In addition to improvements in overall health, the researchers observed that “exercise training programs of high intensity are well tolerated and convey significant aerobic capacity benefits in cohorts composed of older and low-fitness individuals.” 

Clearly, there is considerable evidence to suggest that HIIT is beneficial for a wide range of populations, including older adults. However, you may (rightly) be concerned about whether your older clients possess the ability to perform HIIT on treadmills or other types of equipment where balance and coordination are required. Hwang and associates investigated whether an all-extremity ergometer—a cycling ergometer with moving arms—could successfully be used for HIIT to provide health benefits for sedentary older adults (average age of participants was 65). The study lasted eight weeks and included three groups: one group performed 4 minutes of high-intensity exercise at 90% of peak heart rate followed by active recovery intervals at 70% of peak heart rate; a second group performed steady-state exercise for 32 minutes at 70% of peak heart; and a third group acted as a non-exercise control group. When compared to the moderate-intensity and control groups, the HIIT group experienced greater improvements in health as measured by improved aerobic capacity, mitochondrial density and insulin resistance. The researchers concluded that “eight weeks of all extremity, non-weight-bearing HIIT is safe for sedentary older adults.”

Putting HIIT Into Practice 

Robert Linkul, MS, owner of Be STRONGER Fitness in Sacramento, Calif., designs group fitness workouts that cater specifically to the needs of active older adults. Working with a clientele that has an average age of 68, Linkul believes that age should not be a limiting factor when it comes to helping his clients experience results. “We use intervals of truly challenging work and inform our clients to exercise to a point of ‘discomfort,’” he explains. “We do not have clients wear heart-rate monitors or ask them to achieve specific levels of intensity; however, we do ask them to elevate their efforts to ‘higher’ levels. We see a great benefit in training strength and conditioning components at the same time. Our clients love it and we can achieve great results in short periods of time.”

While the evidence suggests that older adults and those with chronic health conditions can tolerate HIIT, it’s a good idea to begin with a low-volume HIIT protocol when working with a deconditioned individual or a new client. A study commissioned by the American Council on Exercise found that reduced-exertion high-intensity training (REHIT), a protocol featuring fewer and shorter sprints of supramaximal intensity, could provide greater benefits than MICT. The REHIT protocol featured a two-minute warm-up, a 20-second sprint, a three-minute recovery and a second 20-second sprint followed by a three-minute cool down for a total exercise session lasting less than nine minutes (eight minutes and 40 seconds to be exact). Over the course of the eight-week study, the REHIT group experienced more health benefits than the MICT group, which performed 30-minute workouts. Replicating the workouts from this study would be one option for enabling clients and group fitness classes to reap the benefits of HIIT.

When utilizing HIIT with new or deconditioned clients, start with relatively short intervals (10 to 30 seconds) of high-intensity exercise at approximately 85 to 95% of age-predicted max heart rate, followed by longer periods of lower-intensity activity (60 to 70% of maximum heart rate) using relatively stable equipment such as the cycling ergometer with arm action or a rowing machine. Whether they are long-time exercisers or relative newcomers to physical activity, older adults should be able to tolerate one or two high-intensity intervals, followed by active recovery intervals before gradually progressing to performing more work intervals with shorter periods of active recovery. 

Over time, it may be appropriate to apply a standard format such as the Tabata protocol, which features 20 seconds of high-intensity exercise followed by 10-second passive recovery intervals for eight cycles in four minutes. However, before challenging a client with a full four-minute Tabata cycle, think about breaking it up into one-minute segments of two cycles of 20 and 10-second intervals followed by two to three minutes of lower-intensity active recovery. Clients can work up to completing the four-minute interval over time. 

The point is that you can take established HIIT protocols, such as Tabata, and regress them to shorter periods of time and gradually introduce clients or group class participants to the format before progressing to longer periods of high-intensity work. If clients are willing and able, age should not be a factor that limits them from experiencing the benefits of high-intensity exercise.