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High-intensity interval training (HIIT) took the No. 1 spot on the American College of Sports Medicine’s annual Worldwide Survey of Fitness Trends for the first time in 2014 and has stayed in the top 10 ever since. It’s the darling of the fitness world, and there seems to be little that HIIT can’t do.
Characterized by short bursts of high-intensity exercise (anywhere from one to four minutes) followed by short periods of rest, HIIT’s popularity largely lies in its capacity to offer big results in little time. Health and fitness benefits have proved to be similar to or better than those from moderate-intensity workouts that take twice as long.
It’s not just the gym crowd that’s been crowing about HIIT. The research community has been bringing the young, old, fit, unfit and everyone in between into the lab to see whether HIIT’s magic is universal. By and large, it is. Most of the populations studied have benefited from meaningful gains in health and fitness. But what’s still up for debate is whether exercisers find high-energy workouts more enjoyable than moderate-intensity, steady-state exercise.
Panteleimon Ekkekakis, professor and chair in the department of kinesiology at Michigan State University, has spent most of his career studying how different intensities of exercise make people feel. He’s been following the HIIT trend since news of its benefits started circulating among exercise physiologists back in the early 2000s.
“HIIT started to gain traction at an astonishing rate and became this major global phenomenon,” said Ekkekakis, who claims there are roughly 700 published studies a year on HIIT.
In the early days, HIIT was considered more appropriate for athletes and the very fit, but it wasn’t long before fitness experts were suggesting it might prove valuable for the average Joe and Jill. Exercise psychologists like Ekkekakis were doubtful.
“It’s never going to work, because we all know that high-intensity exercise is unpleasant,” he said.
To gain the much-ballyhooed benefits of HIIT workouts, you need to train at 85 to 95 per cent of your maximum effort (peak heart rate), which isn’t for everyone. The no-pain, no-gain philosophy of exercise has always been embraced by the few, not the masses. Despite this, researchers started publishing data suggesting HIIT is not only well tolerated by average exercisers, they actually find it more enjoyable than less intense workouts.
The combination of enjoyment with the promise of significant results in less time is the holy grail in terms of exercise adherence. Lack of time has been cited as one of the main reasons so few people exercise on a regular basis.
Still, Ekkekakis wasn’t buying it.
“It’s a lot more complicated than that,” he said of why the exercise dropout rate is so high. “Most people have discretionary time — they just choose not to allocate that discretionary time to exercise, presumably because they find other things that make them feel better or give them more satisfaction.”
Citing a preponderance of evidence proving that intensity drives people away, Ekkekakis decided to take a closer look at HIIT’s track record for long-term adherence. The results were published in a recent edition of Psychology of Sport and Exercise. Along with colleague Stuart Biddle from the University of Southern Queensland, Australia, Ekkekakis identified eight quality studies comparing HIIT to moderate-intensity exercise, all of which included followups of at least 12 months. What they found is unlikely to make HIIT fans happy.
“While non-adherence and dropout represent great challenges for any form of exercise, especially in unsupervised settings, these problems were shown to be exacerbated with HIIT,” Ekkekakis and Biddle stated in the study. “Compared to moderate-intensity exercise, more individuals assigned to HIIT did not adhere to their prescription when unsupervised, most likely because they could not.”
Not all the study subjects gave up exercise altogether — some just weren’t as motivated to sustain the same intensity on their own as when they were under the watchful eye of an instructor. They took the workouts down a notch or two into a more comfortable, moderate-intensity range. That’s not a bad thing — it’s just that when combined with the short duration of most prescribed HIIT workouts, health and fitness benefits are likely to be less significant than advertised.
So, where did the idea that exercisers preferred HIIT over less intense workouts come from if all eight studies proved that the majority of people eventually gave up on HIIT altogether?
It turns out gauging exercise enjoyment is harder than you might think. People are in no condition to answer questions about how they feel while in the middle of a tough workout. Any inquiries need to wait until after the workout is over. With all the hard work done and most people feeling accomplished with their efforts, their feelings are much different than when they were in full sweat mode.
“After exercise, almost everyone feels good,” Ekkekakis agreed. “But they might feel good because the darn thing is done.”
Does that mean HIIT has been oversold as a solution to sedentary habits? Probably. But that doesn’t make it a bad option. It’s just not for everyone, which puts it on par with most other workouts. The gauge of an effective workout isn’t how successful it is in a lab, but whether you want to do it all over again on your own.
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