Super-short workouts - seven-minute, six-minute, four- minute and even one-minute workouts - are gaining popularity. But while they require very little time, they also demand straining effort.
These workouts are built around the concept of high-intensity interval training (HIIT) - pushing the body almost to exhaustion for a brief spurt of minutes or seconds, and then rest and recover before repeating the intense interval.
Athletes have long used interval sessions as part of a varied weekly training programme to improve their competitiveness.
But Martin Gibala, a professor of kinesiology at McMaster University in Hamilton, Ontario, has helped to popularise the idea that normal people can also rely on high-intensity intervals as their only exercise, and do very few of them while still improving their health and fitness.
Since 2004, Gibala has published multiple studies about the potent effects of intervals.
RACING AGAINST TIME
I don't think we have proven that one type of exercise is substantially better than another, from a physiological standpoint... If the obstacle keeping someone from exercise is time, then HIIT is the preferred exercise option.
MARTIN GIBALA, professor of kinesiology at McMaster University, on why HIIT is a choice among busy working adults.
His most illustrative example was in 2014, when he and his colleagues asked sedentary men and women to complete three 20-second intervals on a stationary bicycle, pedalling as hard as they could manage, with two minutes of gentle, slow pedalling between each interval. This was the one-minute workout.
After six weeks of performing three of these sessions per week, for a total of 18 minutes of intense exercise tucked in to slightly longer periods of less intense exercise, the volunteers were significantly more aerobically fit and healthier, with improved blood pressure numbers and markers of muscular health.
Gibala has written a new book, The One-Minute Workout (co-authored with Christopher Shulgan), which was out last month. It details his research and provides several different, high-intensity interval training workouts, in addition to the one-minute version.
Q People always ask whether intense interval training is actually better than more traditional, longer, slower types of workouts. Is it?
A I don't think we have proven that one type of exercise is substantially better than another, from a physiological standpoint. Both improve health and fitness, but one is far more time efficient.
So if the obstacle keeping someone from exercise is time, then HIIT is the preferred exercise option. I think almost everyone can find a few minutes in their day for a short-interval workout.
Q Most of the studies you describe in your book involve stationary bicycling, which usually means a gym membership that not everyone has. Can other types of activity be adapted for HIIT?
A Absolutely. That's one of the great things about interval training. It only requires that for a brief period of time, you push yourself out of your comfort zone.
You don't have to reach any set percentage of heart rate or anything like that. You just need to feel some brief discomfort.
You can achieve that by running hard to the next signpost when you are out on a trail or picking up the pace while you are walking. You can even complete a very effective HIIT programme in a stairwell during your lunch break.
Q Since the sessions are so short, does HIIT burn many calories and help weight loss?
A Exercise is not a huge contributor to weight control. People don't like to hear that, but it's true. It is much easier to cut calories in the diet than to burn large numbers of them with exercise of any kind.
With HIIT, there is some evidence that you burn slightly more calories than if you had not exercised. But the numbers are small, so it's better to eat less if weight loss is a goal.
Q Is one minute the shortest possible HIIT workout?
A I think one minute may be the limit. We are still looking for the exact sweet spot in terms of how little intense effort people can do and still get significant health and fitness benefits. So far, it looks as if three repetitions of 20-second intervals are the lowest effective load. But we are still experimenting.
Q What is your exercise routine?
A I do something physical every day, and it's not all HIIT. I play a weekly hockey game.
But life is busy. My wife works and we have young kids. So most of the time, it's intervals, sometimes on a stationary bike, sometimes on other equipment in my basement.
I do high-speed pull-ups and push-ups. I'm like everyone else. I fit in as much exercise as I can, when I can, and that would be my advice to anyone.