Next time you do cardio, here’s your workout:
- Warm up at a light pace for 2 minutes.
- Now, push all-out for 20 seconds; recover for 2 minutes at a slow pace.
- Do that 20 second/2 minute interval again.
- End with one more 20-second everything-you-got burst.
- Cool down for three minutes.
You’re done. And that 10-minute workout you completed? It’s just as effective at getting you fit as slogging through 45 minutes of a steady pace on the treadmill, according to a new Canadian study.
Researchers at McMaster University have been studying high-intensity interval training for roughly a decade, and their findings have repeatedly shown that interspersing short bursts of max effort with moderate-intensity stints is a highly effective, time-efficient way to get fit. But until now, it wasn’t clear how sprint interval training (SIT) stacked up against moderate-intensity continuous training (MICT) over a prolonged period of time.
So, for this experiment, the researchers recruited 25 sedentary guys and got an initial read on their cardiorespiratory fitness, insulin sensitivity, and muscle composition and function. Next, they placed the men into one of three groups: the control group, an MICT group, and a SIT group. Three times a week over the course of 12 weeks, the MICT volunteers hopped on stationary bikes. After a two-minute warm-up, they pedaled at 70 percent of their maximum heart rate for 45 minutes, then spent three minutes cooling down. Total time commitment: 50 minutes.
Also three times a week, the SIT group warmed up on their bikes and did the interval routine above. Total time commitment: 10 minutes. The time spent exerting any real effort: one minute.
After 12 weeks, both training groups were in markedly better shape. Not surprisingly, the control group’s numbers didn’t budge. Yet despite exercising for a fraction of the time that the MICT riders did, the SIT group scored the exact same fitness gains. Both sets of men increased their oxygen uptake, a measure of endurance, by 19 percent. Their insulin sensitivity (how well the body handles blood sugar) also improved greatly, potentially lowering their risk of Type 2 diabetes and heart disease. Finally, both groups’ muscles had undergone similar adaptations in response to exercise, all having more and better functioning mitochondria (cellular powerhouses) than when the study began.
These findings don’t suggest that interval training is more effective than traditional continuous-pace training. What they do say is you’re going to get fit a hell of a lot faster. “The number-one-cited reason why people don’t exercise is lack of time,” lead study author Martin Gibala told Men’s Journal. “For some, that’s true; but for many others, it’s an excuse. Now there is a body of research to show that, just as elite athletes use high-intensity interval training to dial in performance, the general population can also get major benefits in a short amount of time.”
Although this type of training has clear advantages, you shouldn’t try going directly from slouch to power sprinter. Other studies have shown that if you’re totally out of shape, starting with SIT may do your body more harm than good. Yes, the men in this study were sedentary, but they completed the protocol under the close watch of trained experts. To be on the safe side, start with some easy cardio and then increase your intensity and duration gradually before attempting to condense your workout down to a few minutes.
One last key point about SIT: No matter your fitness level, you can’t cut corners. “Sometimes interval training research gets misinterpreted,” Gibala says. “People think they can exercise for only a few minutes and get all these health benefits without actually doing the work. ‘Do I really need to go all-out?’ they’ll ask. If you’re devoting the smallest amount of time possible to exercise, then yes, you have to work out really, really hard.”