Wondering exactly how you should spend your time moving your body can be confusing, especially if you want to make the most of your cardio session. Should you lace up for an easy stroll? Jog to your favorite playlist? Or really sweat it out to the latest Peloton class?
While there’s no one “best” way to work out overall—it all comes down to your goals, individual preference, experience, and time you’ve got at your disposal—a new study does provide some interesting intel on how a certain type of cardio just may set the stage for healthier aging.
High-Intensity Interval Training Linked to Beneficial Body Composition Changes
In the study, researchers from the University of the Sunshine Coast in Australia recruited 123 physically active older adults; on average, they were 72 years old with normal BMIs, but were considered overweight by body fat percentage.
The researchers then divided them into three workout groups:
- High intensity: 40-minute treadmill session of 4 reps of 4-minute intervals at 85–95% of peak heart rate with 3-minute recovery periods
- Moderate intensity: 45-minute treadmill session that included 30 minutes of steady, continuous walking at 60–70% of peak heart rate
- Low intensity: 45-minute balance, stretching, and toning class with 30 minutes at 45–55% of peak heart rate
Each group did a 10-minute warmup and five-minute cooldown.
Participants in each group completed three sessions a week for a total of six months. By the end of the study, the researchers discovered that people in both the high-intensity and the moderate-intensity group lost a similar amount of fat mass and visceral fat, the deep kind that wraps around your organs and research links to conditions like type 2 diabetes and heart disease.
But there was one important difference: Those in the moderate-intensity group also showed a decrease in lean mass, or the amount of muscle tissue, while those who did high-intensity exercise were able to preserve their muscle while losing fat.
The researchers believe that high-intensity exercise puts greater force on the muscles and triggers greater levels of something called protein synthesis, or the building and repairing of muscle tissue. “Combined, these factors could contribute to improved muscle maintenance,” they write.
That’s crucial, particularly as we get older, Timothy Coyle, M.S., an exercise physiologist and ACE-certified personal trainer at the Hospital for Special Surgery in New York, tells Prevention. While lots of people tend to focus on losing fat as a way to improve their health, preserving muscle and staving off its age-related decline is vital.
“After 60 or so, sarcopenia starts to accelerate,” he says. “Strength and power play a huge role in our everyday function; their loss increases things like fractures and fall risk, and everything that comes with that.”
Simply put, maintaining muscle can help you continue to do the tasks you do every day and keep you independent.
What HIIT Actually Is—And Why It’s Less Intimidating Than You May Think
The crux behind high-intensity interval training, or HIIT, comes from both the “H” and the “I” in its acronym, Coyle says. Basically, the exercise has to feel hard—but only during short bursts, not for the entire duration. Interspersed between those intense interval efforts are light periods of active recovery, which allow your body to go hard all over again until your workout is complete.
As for how hard you should go? One of the beauties of HIIT is that it’s not governed by set paces—it’s all based on what feels intense to you.
In general with HIIT, you should shoot to work between 80% and 95% of your maximum heart rate during your intervals, says Coyle. If you don’t know your max or don’t have a way to measure your heart rate, that’s perfectly fine—using your rate of perceived exertion is a great way to determine it (if you’re taking certain meds like beta blockers, which lower your heart rate, you’ll want to use this method, too, he says).
On a scale of 1 to 10, with 10 being absolute max, can’t-do-a-thing-more effort, HIIT should land between a 7 and a 9, Coyle says. That means: if you’re working out with a buddy, you’d be able to eke out a few words, but not a full sentence. “If you can say more than six words, it’s probably too easy,” he says.
For example, a brisk walk or a jog might be enough to bring you to that 7 to 9 range—it doesn’t necessarily need to be a blistering sprint. “High intensity is relative to you,” says Coyle. That’s what makes this form of fitness so beneficial—it’s highly individualized.
How to Add HIIT to Your Workouts
A good way to start adding intensity to your workouts is by using the four minutes on, three minutes off programming from the study, according to Coyle. If you haven’t added intensity to workouts before, try to do four rounds. But rather than striving to meet an “ideal” intensity off the bat, simply alternate between slight pushes (more effort) and subsequent back-offs (a more relaxed pace), with the goal to finish so you can see how it feels.
“Start light,” he says. “Don’t kill it on the first day.” Instead, focus on frequency, aiming to complete—and feel good about—this less-intense version two to three times per week. Keep your intensity in check for the first couple weeks of this, he says.
You can also try shorter, more intense efforts where you really try to push it, says Coyle. These are more time-efficient and allow you to produce more power than you could sustain during longer work intervals. Go for 20 to 30 seconds—hard enough so you can only get out a couple words—with recovery periods roughly twice as long (so, 40 to 60 seconds). “You want to be able to give out a similarly high output in the next interval,” Coyle says, which is why you need longer recovery.
There’s no one modality that’s better than others for these. If you’re already used to jogging, you can run for the intervals. But if you’re not a runner or want to avoid high-impact exercise, you definitely have other options, per Coyle.
You can try:
- Power walking
- Treadmill for incline walking
- Rowing machine
- Elliptical
- Spin bike
- Stepper
Taking the time to do a proper warmup before HIIT is crucial. “A solid warmup warms the muscles and brings oxygen and nutrients to the working muscles, increases your range of motion, and directly prepares you for what you’re about to do,” Coyle says, all of which can help prevent injury.
So before HIIT, do a few minutes of light cardio in the mode you’ll be using for intervals and some dynamic stretching that hits the muscles that will be working, like your hips, hamstrings, and quads. Walking hamstring scoops and clamshells are solid choices.
If you’re just beginning a HIIT program, it’s probably best to do a workout on its own. But after a few weeks or months, you can also tack HIIT onto the end of a strength training workout, because not only are your muscles already warm and mobile, but resistance training is the gold standard for stimulating muscle protein synthesis, which, like we mentioned, is key for maintaining muscle mass.
If you’re doing HIIT at the end of a strength workout, three to five intervals is a solid number to shoot for, Coyle says. If you’re doing it as its own workout, aim for eight to 12 intervals.
Finally, folks with cardiovascular, metabolic, or kidney conditions should talk to their doctor before starting any kind of exercise plan. The same applies if you notice any red-flag symptoms, like shortness of breath, dizziness, or pain or discomfort in the chest, neck, jaw, or arms. And regardless of any health conditions or symptoms, make sure you listen to your body during your intervals and back off if they feel too intense.
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