Fitness: The benefits of HIIT workouts might be maxed out
When it comes to claims that High Intensity Interval Training gets rid of fat and builds muscle, the jury’s still out
The “lots of pain, lots to gain” approach to exercise isn’t meant for everyone.
It seems like every second headline these days is selling the benefits of HIIT (High Intensity Interval Training). Amid claims that it’s an express pass to losing weight, building muscle and increasing aerobic capacity, it appears as though there’s nothing that HIIT can’t do.
Defined as workouts that feature short bouts of high intensity exercise followed by equal or slightly longer periods of recovery, HIIT was first lauded for offering improvements in cardiovascular fitness similar to workouts that took twice as long. There is a caveat: HIIT demands exercisers work out at 90-100 per cent of maximum effort. That means exercisers need to push their body to its physical limit each and every interval.
This “lots of pain, lots to gain” approach to exercise isn’t meant for everyone. In fact, during the early days of HIIT research, there was a caution that it might not be safe for anyone unaccustomed to intense exercise. And it was definitely out of bounds for the obese and those trying to manage chronic disease.
But in the last few years, there has been more talk that HIIT shouldn’t be limited to helping the fit get fitter. New research suggests the time-efficient benefits of HIIT can still be gained by performing intervals that aren’t quite as demanding as first proposed. Instead of 30-second intervals executed at an all-out sprint-like intensity, intervals of one to three minutes at closer to 80 per cent of maximum effort, followed by up to five minutes of lower intensity exercise are now considered effective HIIT workouts.
Does dialling down intensity mean that HIIT is now an equal opportunity workout? In other words, do the benefits of short bouts of high intensity exercise outweigh the risks — even among those with chronic disease, excess weight, or limited exercise experience? Or is all the hype around HIIT typical of most fitness fads, over-promising and under-delivering?
Keep in mind that when we talk intensity, we’re talking about workouts relative to one’s own level of aerobic fitness. For the unfit, that could mean repeated bouts of fast walking followed by easy recovery intervals, versus the Usain Bolt-like sprints that are more typically associated with HIIT.
What type of benefits are we talking about? Several studies have confirmed that HIIT workouts improve cardiovascular fitness as effectively, or more effectively, than moderate intensity workouts that typically take twice as long. And there’s little doubt that the health benefits associated with improved fitness, reduced risk of heart disease and metabolic disorders, are also a byproduct of HIIT. But how does it measure up against some of the other claims associated with this so called “miracle” workout? Does it get rid of unwanted fat and build muscle?
In these two areas, the jury’s still out. A recent meta-analysis done by a team of French researchers investigated the effect of HIIT workouts on total, abdominal and visceral fat (the fat that surrounds your internal organs — not the type that rolls over your waistband) on non-athletic subjects. The results showed HIIT to be effective in reducing fat in overweight or obese subjects, but not in so called “normal-weight” exercisers. It also indicated that HIIT sessions involving running were more effective at reducing abdominal and visceral fat than cycling intervals. Also noteworthy is that higher intensity HIIT sessions (above 90 per cent of maximum effort) were more effective at reducing overall fat stores, while lower intensity workouts were better at decreasing abdominal and visceral fat.
That’s the good news. When it comes to building muscle, however, HIIT workouts aren’t designed to improve strength. They don’t overload muscles in the same way a weight training workout does, so HIIT enthusiasts shouldn’t expect to see significant improvements in muscular strength. Be careful not to confuse muscular endurance with strength. HIIT workouts that feature body weight exercises will more than likely result in small gains in muscular endurance and strength among the untrained, but if more muscle and more strength is your primary goal, HIIT won’t get you there.
But it’s not just the physiological improvements associated with HIIT that’s worthy of study. It’s also important to determine whether HIIT is sustainable given that its effectiveness is based on pushing the body to perform at its maximum, a feeling designed to be uncomfortable. Will the trade-off in time be worth the extra effort in the opinion of already reluctant exercisers?
Like any form of exercise, its value is achieved only when performed regularly. So while some people are motivated by the challenge of pushing their body to the limit, even more dread the idea that every workout will require herculean effort and fortitude to complete. The real decision about whether to give HIIT a try is less likely to be related to its potential benefits and more likely to be based on how much you value the savings in time versus the effort it demands.
A final word of caution: even though HIIT workouts are now considered safe for an increasingly wider range of Canadians, those with uncontrolled diabetes or hypertension or with a history of cardiac events should stick with more moderate intensity workouts unless cleared by their physician.
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