You don't need to be working out for longer, but you should probably be working harder—in spurts, at least.
Studies have shown that interval training can help people burn more fat, and increase fitness levels even after just 15 or 20 minutes of exercise. And a new study found that people with Type 2 diabetes benefited more from interval walking—their blood sugar was more controlled—compared to people who walked continuously.
"The return on investment of interval training is fabulous, and it keeps exercise interesting," says Richard Cotton, the National Director of Certification at the American College of Sports Medicine, who was not involved in the new research. "Walkers can incorporate interval training by warming up and walking for three minutes and jogging for one minute and repeating that pattern for let's say, 30 minutes."
Interval training means alternating between different intensities of exercise and allowing time to rest in between bursts of action. This can mean simply speeding up your walk to a jog for a few minutes or, in the more extreme, it can mean high-intensity interval training (HIIT) and Tabata. But they're all based in the same idea: short explosions of exercise that get your heart rate up followed by periods of rest or lower intensity provide a greater benefit.
Martin Gibala, the chairman of the department of kinesiology at McMaster University in Hamilton, Ontario has been studying interval training for years, though his focus has been primarily on very intensive exercise like HIIT. Some of his recent research has looked at whether quick HIIT sessions can stimulate similar fitness levels as moderate-intensity continuous training.
"There’s a very large growing body showing interval training can be safely applied to many different people, including those with chronic diseases," says Gibala. "Interval training can be scaled to any starting level of fitness. If you have a high level of fitness, the speed on the treadmill will be different from someone less conditioned"—but the benefit will be similar.
Here's why interval training is thought to work. By changing up exercises in a single period, exercisers are improving both their endurance and speed during one exercise session. There is also thought to be a benefit of reaching your "total maximum capability"—basically working your body as hard as you can—which is hard to do for a long period of time. "You increase your heart rate and total intensity to a higher level than you could during continuous activity," says Cotton. "Almost everyone can do something continuously at 50% of their maximum ability. But, you if you can take it to a higher intensity in short bouts, your body gets stimulated in ways it wouldn't otherwise."
Interval training doesn't have to be difficult, but when it's taken up a notch—as it is with HIIT and Tabata—researchers have seen even more benefit. The Tabata Protocol is a kind of HIIT method based on studies by Japanese researcher Izumi Tabata. His original 1996 study monitored athletes as they cycled at their absolute highest intensity for 20 seconds, followed by 10 seconds of resting, and repeated. Since then, several gyms have developed their own versions of his workout.
The research on interval training—regardless of ultimate level of intensity—is encouraging. It shows that mixing it up provides more benefits, and keeps things interesting. It's not for everyone, since some people may find upping their fitness levels in various cycles too challenging, while someone running a marathon needs to dedicate lots of time to continuous exercise and long runs. Gibala also adds that the field is relatively new, and so far most studies have looked at the impact of interval training in the short term, not long term. Still, science shows not having enough time to exercise is not an excuse.