Researcher and author Martin Gibala, Ph.D., explains how.

Interval training, especially high-intensity interval training (aka HIIT), has been considered the holy grail of cardiovascular workouts. And while common knowledge about HIIT is to make sure you have at least 24 hours between workouts, the approach to time and intensity remains debatable.

Meet Martin Gibala, Ph.D., professor and chair of the kinesiology department at McMaster University in Toronto. His research into how little exercise can you do and still get benefits led him to write the recently published book “The One-Minute Workout: Science Shows a Way to Get Fit That’s Smarter, Faster, Shorter” (Avery, 2017).

Here, 24Life talks to him about his research.

24Life: Why did you decide to look at short duration interval training?

Martin Gibala: We’ve been conducting research on interval training for about a decade. Obviously, it has become an extremely popular form of training.

We wanted to push the envelope a little bit to basically try to get at these questions around how low can you go? So we had 14 healthy, overweight and sedentary men and women do a 10-minute workout three times a week where during just one minute they were working at 110 percent that was broken up into three 20-second sprints.

It’s still quite fascinating to me from a scientific perspective that you can do such a small amount of exercise and still stimulate a lot of these beneficial adaptations that we associate with improved health.

24Life: What were some of those results?

Gibala: There are four main outcomes that are important. The first one is cardiorespiratory fitness, or cardio fitness, which we measure objectively as maximal oxygen uptake, or VO2 max. It is one of our best predictors of all-cause mortality and your risk for developing many chronic diseases. That improved after six weeks of training quite robustly; we saw a 12 percent improvement in cardiorespiratory fitness over six weeks. That’s a meaningful improvement because that would translate into about a 15 percent reduction in your risk of developing some of those chronic diseases. Point being that fitness was robustly elevated in a short period with a very short amount of exercise.

Second, we looked at what was in the muscles. We obtained biopsies and we looked at the mitochondrial content of the muscle, which is a good indicator of muscle health. Essentially, mitochondria are the components of the cell that convert fuels like sugars and fats into energy by using oxygen. If you have more of these mitochondria, you’re essentially more efficient at using oxygen to produce energy. And we know that increasing your mitochondria content is also associated with a lower risk for developing chronic diseases, especially Type 2 diabetes.

The third one would be a measure of basically how well you handle blood sugar. What we saw was that blood-sugar handling capacity was improved—at least in men but not women. We looked at the average blood-sugar concentration over 24 hours by measuring it a couple of different ways. What we saw in the men was that  average blood-sugar concentration was reduced. And that would be associated with a more positive health profile.

That fit with some of the muscle measurements that we made. There’s certain compounds in muscle that are responsible for transporting blood sugar, essentially bringing the sugar out of the blood and into the muscle. We saw that the transport protein, GLUT4, that’s responsible for that was much more elevated in the men compared to the women after training.

We didn’t see a significant change in the women, but it was a small study. I think there were only seven to eight people in each group, but it suggests that there might be some sex-based differences in the adaptive response to interval training. That’s been suggested in a couple of other studies, as well. Certainly, we need more research there to follow that up.

One last thing worth noting in our study: A meaningful result was the reduction in blood pressure. That’s associated with risk for developing some chronic diseases. We saw that this very short intense training was sufficient to reduce blood pressure in our subjects.

24Life: You saw these effects with sedentary people. What if the population was more fit?

Gibala: The short answer is I would expect improvements, perhaps to the same degree. And there’s some data to back that up: There’s been a study performed at Queen’s University in Canada, where they essentially used a very similar protocol, not identical but with a more fit group of subjects, and they showed improvements in cardiorespiratory fitness and some changes in muscle, as well. They didn’t necessarily have all the blood-sugar measurements that we included.

24Life: How does this training compare to more steady-state training?

Gibala: That is another question and something we’re following up on, as well. We have done a 12-week study where we basically compared the results between two groups: one using this 3×20-second protocol and one using 150 minutes per week of traditional moderate-intensity continuous training.

What we found in that study is the improvements in cardiorespiratory fitness, or VO2 max, were identical between the two groups over 12 weeks, even though the sprint group did a lot less total exercise and their time commitment was about five times lower, as well. In these head-to-head comparisons over 12 weeks, the protocols give you similar improvements in your fitness despite these huge differences in the amount of time you have to spend and the total amount of exercise that you’re doing.

24Life: In light of this other research you’re doing with endurance and submaximal intervals, is one possibly better than the other?

Gibala: In the big picture, we have very robust evidence based on very large-scale studies that support the public health guidelines calling for roughly 150 minutes per week of moderate-intensity exercise.

An analogy I’ll use sometimes is borrowed from the pharmaceutical industry: The public health guidelines for exercise are like the long-established drug of choice on the market. There’s ample evidence to show that that type of training can be very beneficial both from observational studies and epidemiological evidence. Interval training is a bit like the new drug on the market. It is showing a lot of promise in these early phase trials, basically relatively short-term studies. But we don’t have anywhere near the evidence to equate them because we just haven’t done these large-scale randomized clinical trials or followed people over decades—for example, to show that death rates are reduced.

But I think that’s where the field will be going at least in terms of making these randomized, clinical-trial-type comparisons of short intense interval training versus traditional endurance-type training. That’s the type of evidence we will need to say yes, one is better than the other, or in fact you can get very similar results even though you can train quite differently, one requires a lot less time. I think that’s a fair way to look at it.

24Life: Is there anyone who shouldn’t be working out at these really high intensities?

Gibala: In terms of potential negatives, are there some? Sure. I think the first one is that people are enamored with only having to do a few minutes a week of exercise or this idea of low-volume exercise, but I’ll often say, there’s no free lunch. This type of training is very uncomfortable. The intensity that’s required is very high.

Some people may not like this form of training, and that is often held up as a criticism, and people say this is a barrier to people adopting it. That’s true, but let’s be realistic about how many people are adopting our current public health guidelines: It’s not very good. So our counter to that is, even if we can identify 5 percent of the population that might prefer to adopt this type of training, you do the math in terms of long-term savings for health care and it’s quite significant.

We think there’s value in the approach, but we recognize that this isn’t going to be for everybody and that some people may really dislike this form of training. Then probably a varied approach to training is going to be your best bet over the long term.

In terms of safety, clearly there’s going to be groups of individuals that should not be doing this type of training and might be contraindicated for them. But I would temper that by pointing out that there’s a lot of interval training research now that shows that many different individuals—including those with chronic diseases, cardiovascular disease, coronary artery disease, metabolic syndrome, diabetes—can benefit from performing interval training. But it’s not necessarily these all-out protocols.

So would we suggest that a person who has heart disease just jump on their bike and pedal their hearts out? No, absolutely not. However, we know there are other types of interval training strategies that might be very suitable for those individuals and allow them to improve their health and fitness.

24Life: Is there anything the public should walk away with from your research?

Gibala: That short, very intense efforts can considerably improve your health and fitness. I think that’s the main take-away for people: That these short, intense efforts can be very effective if you’re willing to do them, and for that matter, if it’s safe for you to do them.

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