If you've heard of interval training, you can probably thank Martin Gibala, professor and chair of the kinesiology department at McMaster University in Hamilton, Ontario, whose research has helped popularize the time-saving exercise technique.
Interval training comes in many different flavors, but the general idea is to alternate periods of relatively intense exercise with recovery, either low-intensity exercise or rest. It can be a much more efficient way to get the benefits of exercise than longer workouts at an easier pace, says Gibala.
And it's not only for athletes; it's been studied in sedentary adults and people with heart failure, Type 2 diabetes and other ailments.
In his book The One Minute Workout: Science Shows a Way to Get Fit That's Smarter, Faster, Shorter, which comes out Tuesday, Gibala explains the physiology and history of interval training and includes a dozen workouts. And yes, one of them is based on just one minute of hard exercise (with another nine minutes of warm-up, recovery periods and cool-down), which in a small study conducted by Gibala and colleagues improved markers of health comparably to a 45-minute session of steady, moderate exercise. We talked to him about the benefits of and misconceptions about interval training. The interview has been edited for length and clarity.
When people talk about interval training, what do they mean?
Broadly, there are two main types. High intensity interval training, or HIIT, would be intensities that are generally higher than what we see in public health guidelines. It's a heart rate exceeding 80 percent of a person's maximum, but not going all out. Sprint training is harder than that — an all-out pace.
Which provides the bigger benefit?
Clearly there's a trade-off between intensity and duration. The more intense the effort, the less duration required to reap the benefits. So sprint training is the most efficient, but it's not for everyone. It's less widely studied. We know a lot more about the adaptations the body makes with HIIT.
Do we know what's going on in the body to make these short bursts of exercise effective compared to longer sessions?
I'll talk about the muscles, since that's what I know most about.
The underlying cellular and molecular events largely seem to be similar. You want to create more mitochondria, to increase the capacity of muscles to burn sugars and fats. You can trigger that in different ways. You can do moderate intensity exercise, which continuously stimulates the muscle for a prolonged period of time. Or you can do short, very intense bursts of exercise. Or you can do something in between. Generally speaking, the results are the same. The fuel gauge can slowly drop over time or drop really quickly if you step on the gas really hard. The same basic process is triggered, but in less time with intervals.
What is the biggest misconception or myth you see about HIIT?
People tend to view intervals only as this all-out, as-hard-as-you-can-go, very intense exercise. That either scares them off or it makes them think that type of exercise isn't suitable for them. The point I try to make is that interval training comes in different flavors.
Even with interval walking, there's some evidence that it's the better way to go in terms of blood sugar control and boosting fitness [than steadier, slower walking]. But of course you should check with a doctor before starting a new exercise program. [People with unstable angina, for example, are not likely good candidates for interval training.]
In some quarters, I see a move to demonize traditional cardio. That's clearly wrong. The public health guidelines are based on great science, but only about 15 percent of the population is listening. So I want to give people more menu items to choose from.
What if you are training for a 10K or even a marathon? Can you get by with interval training?
Could you run a marathon by only training with intervals? Yes, but I'm not sure you'd run the best marathon that's in you. Elite athletes will still use a blend of about 80 percent traditional high-volume, continuous training and about 20 percent interval training. It goes back to time efficiency. If time is restricted, it's a good way to train.
But there are health risks of higher intensity exercise, especially for older people or those with health issues. What should people watch out for?
I talked to Paul Thompson (the director of cardiology at Hartford Hospital in Connecticut) about this. He says that if it comes down to remaining sedentary or doing something, you're better off doing something. But acute exercise [temporarily] elevates the risk of an adverse event. That's more than offset by lowered risk during the rest of the day, when you're not exercising. But you don't know if you're silently at risk. So it comes down to common sense. If you're older or just starting out, gentler forms of intervals are a good way to benefit.
There's competing evidence on whether interval workouts are more or less appealing for people than slower exercise: They can save time, but are also more uncomfortable. How do you get over that?
Even I don't want to do it every day! Sometimes I want to go for a walk in the woods with my dog. But people have a misperception that exercise is only good if you have 45 or 60 minutes at a time. You can fit exercise into life, rather than structuring life around exercise.
Katherine Hobson is a freelance health and science writer based in Brooklyn, N.Y. She's on Twitter: @katherinehobson.