HIIT for Longevity: How Hard You Should Actually Go?

More vigorous exercise means more healthy years.

That was the message of a study published in Nature Communications in October of last year. Conventional wisdom has long held that vigorous exercise is about twice as good as easier movement for your longevity[lon-jev-i-tee]nounLiving a long life; influenced by genetics, environment, and lifestyle.Learn MoreClose. But when scientists looked closer at data from more than 73,000 people, they found that intense work was actually much more impactful than previously thought: Instead of a minute of vigorous exercise being as good as two minutes of easier exercise, the vigorous movement was worth four to nine times more than the slower stuff when it comes to living longer.

It’s just another reason to dive into high-intensity interval training, or HIIT. For the uninitiated (or those who have just been nodding along when others talk about it), HIIT’s just a fancy way of saying fast-slow-fast. In high-intensity sessions, bursts (or intervals) of higher intensity exercise are alternated with periods of easier intensity or complete rest. Training like this has been shown to help exercisers improve their blood pressure and fasting glucose levels, lower waist circumference and resting heart rate, and increase their aerobic capacity at similar levels to steady-state work, but in much shorter workouts. And scientists are still learning more about its benefits, despite this type of training having been done since at least the 1950s.

“Sometimes I can’t believe I’m still studying interval training after 20 years,” says Martin Gibala, Ph.D., a professor of kinesiology at McMaster University in Canada and one of the preeminent scholars in the field, who even has a type of interval training named for him. Gibala highlights that many of the earliest studies on HIIT were small, and scientists like him are still verifying those results in larger studies, and finding new benefits not only for athletes, but also for people who are overweight, those recovering from surgeries, and more.

There’s good news on the “regular people” side of those studies: While the athletes that are studied are often doing all-out, hair-on-fire HIIT efforts, mortals can reap longevity sessions with shorter, easier sessions that don’t need to be done every day. Here, Gibala and Mark Kovacs, Ph.D., C.S.C.S., founder of the Kovacs Institute, talks you through how your HIIT can (and should) differ from that of an elite athlete, and how to figure out how much of this vigorous movement you can handle each week. And at the end of the article, you’ll find a simple upper body strength-and-cardio HIIT workout from Andrea Lepcio, founder of Mighty Fit in Bar Harbor, Maine.

The Longevity Benefits of HIIT Training

One of HIIT training’s biggest benefits is a boost to one of the most important indicators of overall fitness: VO2 Max[vee-oh-too maks]nounA measurement of how much oxygen your body can use during exercise.Learn MoreClose. Also called “maximal oxygen uptake,” it’s a measure of the peak amount of oxygen that your bloodstream can deliver to your muscles which then convert it into cellular energy. The higher someone’s VO2 Max, the fitter they are, and the longer they can move. It’s no wonder, then, that some of the highest VO2 Maxes ever recorded are among Tour de France champions, with numbers topping 90 ml/kg/min of O2 delivered to their pedal-pumping muscles.

It doesn’t just give you the pedal strokes to climb the Alps, though. A higher VO2 Max is tied to a longer life. In one study that followed 5,000 men over 46 years, adding just one unit of VO2 max increased their lifespan by 45 days. 

HIIT training, Gibala explains, can bump your max by much more than that, and do so in a matter of months.

“The average VO2 max for an average adult is about 35 units… with three months or so of structured [HIIT], the average is about a 10- to 20-percent increase,” he says. For the layperson, that’s a bump of 3.5-7 units of VO2 Max, which has huge implications for healthspan[helth-span]nounThe number of years you live in good health, free from chronic illness or disability.Learn MoreClose given that “a one-unit increase is associated with about a 15 percent lower risk of dying, and a 15-20 percent lower risk of developing cardiovascular and other diseases.”

HIIT also benefits longevity in other ways:

• Cognitive boost: In a 2025 study published in Aging and Disease, adults who performed HIIT on a treadmill three times per week for six months saw greater improvements in the function of their hippocampus – an area of the brain that’s important for memory – than others who did lighter work, like steady-state walking. The HIIT brain benefits had staying power, too, lasting for five years after the study.

• Healthier mitochondria[mahy-tuh-kon-dree-uh]nounOrganelles in cells responsible for producing energy (ATP), often called the powerhouse of the cell.Learn MoreClose: As we age, organelles in our cells called mitochondria start to malfunction; since these mitochondria, the “powerhouses of the cell,” are responsible for creating the fuel our cells need to function, this dip in their quality and numbers means we’re more fatigued, and more likely to suffer from metabolic dysfunction. 

HIIT makes our mitochondria young again—literally. In 2017, the Mayo Clinic published a study showing that HIIT training (and HIIT combined with strength training[strength tray-ning]nounResistance-based exercise to build muscle and support healthy aging.Learn MoreClose) was better at creating new, fresh mitochondria than steady-state training. HIIT also improves the efficiency of our existing mitochondria. 

• Stronger muscle: Starting around age 40, we start to lose around 1 percent of our muscle mass[muh-suhl mas]nounThe total weight of muscle in your body, critical for longevity.Learn MoreClose each year, and the more we lose, the higher our risk of early death. HIIT training, even when done using cardio methods, can help maintain muscular strength. In a research review published in 2025, scientists found that in adults, HIIT training increased strength by an average of 12 percent in the studies they analyzed. HIIT also reduced fall risk among adults, a key risk for wrecking healthspan, by 23 percent.

When combined with strength training, HIIT can also build muscle, Kovacs adds. Many adults who perform resistance training stagnate or lose muscle, he says, because they never increase their intensity — they start the year doing an exercise for 3 sets of 10 with 25 pounds, and they finish the year doing the same. Manipulating time as a variable, either through reduced rest or fitting more reps into the same amount of work time, can increase the intensity of those strength workouts. This type of increase, called progressive overload[pruh-gres-iv oh-ver-lohd]nounGradually increasing workout intensity to build strength and endurance.Learn MoreClose, is key to building muscle, Kovacs states.

HIIT for athletes vs. HIIT for longevity

When scientists put athletes through a HIIT gauntlet in the pursuit of performance benefits, the intensity of the workouts is really, really high: In the original 1996 “Tabata” study, for example, subjects worked for 20 seconds in each interval at a pace that was 170 percent of their VO2 Max… a level that would make most of us want to vomit.

This level of effort isn’t just uncomfortable, Kovacs says. It’s impractical for most people to push themselves to that level, and unsafe for those with cardiovascular risk.

It’s also not necessary. Unlike elite athletes, Gibala points out, most regular exercisers can reap benefits from efforts that rank at a 7 out of 10.

“So you’re a little out of breath. You couldn’t carry on a conversation with your workout partner, but it’s not an extreme form of exercise or effort for most people,” he says. “And you’re dipping into that range, but you don’t stay there for very long — maybe 30 seconds to a minute, and then you back off and do that maybe four or five times.”

As little as four minutes per day of vigorous physical activity of this kind is associated with 25 percent reductions in early death.

To get to those absurdly intense levels, athletes usually perform their interval efforts with cardio machines like rowers, bikes, or treadmills. But when your efforts only need to hit 7/10, you’ve got options, Kovacs reminds us, which is why he suggests combining high-intensity training and strength training into a single workout.

“The important part of resistance training is safe progressive overload,” he adds, an increase in the amount you’re lifting or using over time. This can be accomplished by using more weight on an exercise, performing more repetitions in each set, more repetitions in a certain period of time, or more sets overall. When your strength training progressively overloads, you progress, getting stronger and building more muscle. But most people don’t do it, he says. They go through the motions, never increasing their weights or intensity.

By combining your resistance training with your HIIT, he remind us, you can get the 7/10 benefits while getting stronger and more muscular. Choose exercises where you can control the weight and the movement well, so that you’re not at risk of injury, and perform exercises for sets where you can do 6-10 repetitions before you’re almost failing, leaving 1-2 repetitions in the tank at the end of each set. Do the next set while you’re still a little breathless to fall in the HIIT range.

To keep intensity up with her clients, Lepcio likes to use time as the limiter when combining strength and cardio. She’ll set a time for each set, like 30 seconds to one minute, and then have them perform a strength move for an “AMRAP,” short for “as many reps as possible.” They’ll rest for an equal amount of time, and then repeat that move or go to another.

Over time, Lepcio’s clients progress in these sets by increasing the number of repetitions they can do in the time period, increasing the duration of work, or reducing the length of the rest period … or by changing more than one of these variables. All three allow them to continue to overload their muscles so they get stronger while taxing their heart at the longevity-boosting “vigorous” level.

How much HIIT should you do? And how often?

People can handle a lot of HIIT, and the results can pile up fast. Case in point: Back in 1977, scientists put eight cyclists through a brutal HIIT regime where they worked out for 6 days per week, including three HIIT days consisting of six intervals of 5 minutes each at their VO2 Max. On the other three days, they ran as far as they could in 40 minutes. 

After 10 weeks, they’d improved their VO2 Maxes by an average of 16.8 units.

This kind of intense regimen wouldn’t just be terrible to complete, it would likely cause most of us to get hurt. And you can get smaller, but still remarkable, results in just three sessions per week: In a study co-authored by Gibala that was published in August 2025, “insufficiently active” young adults were able to increase their VO2 Max by an average of 5.6 units in 6 weeks with three weekly HIIT workouts, and their efforts were much shorter: Each all-out, high-intensity interval lasted just 20 seconds, and they did just three of them in each 10-minute workout.

Kovacs recommends a similar protocol: 2-3 sessions of higher-intensity lifting each week. His suggestion is to choose a few multi-joint exercises to do all year long, and try to progressively overload them in your intervals over the course of the year. These multi-joint movements, like goblet squats, lunges, trap bar deadlifts, and leg press, will make it easier to get your heart rate in that 7/10 effort zone since more muscles are involved in every rep.

In Lepcio’s view, certain trainees can handle more HIIT each week — up to six sessions — but the amount of weekly HIIT you can do is about assessing your fatigue week to week. Be honest with yourself: If you feel better doing four sessions per week than five, take the extra rest.

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