We all know we should exercise, but how much do we really need?

Most fitness guidelines recommend we aim for about 150 minutes a week of moderate exercise, such as walking or bike riding. But a number of studies have emerged in recent years that suggest that if we push ourselves hard in our workouts, we can get by on just a few minutes of exercise a week.

So who’s right?

That’s what Prof. Martin Gibala from the Department of Kinesiology at McMaster University wanted to know. For the last decade, Gibala has been studying high-intensity interval training -- meaning workouts that call for hard exercise for a few minutes, rest, then hard exercise again.

His latest work shows interval workouts area great way to improve fitness not just for elite athletes, but also those with chronic health conditions, such as Type 2 diabetes.

Studies of high-intensity workouts have been making headlines for several years now, Gibala says.

“We were interested in the question: how little exercise can you get away with?” He told CTV Toronto from his research lab in Hamilton, Ont.

His team experimented with different variations of intervals, interspersing rest between intervals of “extremely demanding” exercise. (How demanding? Gibala describes it as “a pace that you would ride at to save your child from an oncoming car.”)

Some high-intensity workouts promised results in as little as seven minutes, but Gibala says that may not be safe or practical, especially for people with heart issues.

“So we’ve been looking at modified forms of interval training that are still time-efficient,” he said.

What they came up with was one minute of hard exercise followed by one minute of recovery, repeated 10 times -- 10 minutes of exercise over 20 minutes. Repeated three times over a week, it adds up to 60 minutes a week. “That’s significantly less than public health guidelines recommend, but even after two weeks we see improvements in health and fitness,” Gibala says.

For example, in one study he worked on with people with Type 2 diabetes, six sessions performed over two weeks led to significant drops in blood sugar levels. Middle-aged people who are sedentary also benefitted, his research has found.

“Basically, their heart becomes a better, stronger pump, your blood vessels get more elastic and that's helpful to allow blood and oxygen to flow. And your muscles get better at using that oxygen, so you feel less tired,” Gibala explained.

It’s best to be examined by a physician before beginning any new form of exercise and to get advice from a certified personal trainer, Gibala recommends, but he says interval training can be scaled to any level of fitness. And many forms of exercises are well suited to interval training, including cycling, running, and swimming.

“Many more people than we initially thought can benefit from this type of approach,” he said.

So while 30-minute long, five-times-a-week workouts might still appeal to some, for those who lack the time and the discipline to exercise that often, high-intensity workouts may be the way to go.

With a report from CTV Toronto’s Pauline Chan