Do high intensity exercises affect our heart? Mind? Life expectancy? Waist?

For the past five years, high intensity interval training (HIIT) has been one of the most popular and controversial forms of exercise. Consisting of short periods of intense exercise interspersed with breaks, various versions of HIIT have been scrutinized, tested, debated, and sometimes ridiculed by countless researchers, trainers, journalists, influencers, and just about anyone else interested in fitness training.

Gym franchises and online classes specialize in HIIT. Dozens of scientific studies monthly explore its benefits and drawbacks. Wherever you look, HIIT is all the rage.

However, there are still many questions about HIIT. Is it very good for our heart? Mind? Life expectancy? Waist? Is it better for us, in the long run, than taking a brisk daily walk? And what does “intense” exercise really mean?

With New Year’s resolutions to exercise almost around the corner, this seems like the right time to dig into HIIT, and wonder how and why to try it. It’s also helpful to explore the best way to practice HIIT, as well as whether we need to have an expensive heart rate monitor, a gym membership, a personal trainer, and advanced math skills to get started, or if a pair of running shoes, a practical hill. And a distant tree is more than enough

What is HIIT?

With HIIT, you ride, run, swim, jump, do sit-ups or exert yourself vigorously aerobically for a few minutes or even seconds, slow down or stop to rest for another period of time and repeat that sequence three or four times. or more. The goal is to “challenge” your cardiovascular system and muscles during each interval without falling into extreme exhaustion or injury, said Martin Gibala, a professor at McMaster University in Hamilton, Ontario, and a prominent HIIT researcher.

One of its most attractive aspects is that HIIT sessions generally require less than 10 minutes in total.

This exercise strategy is not new, of course. Athletes seeking performance improvements have included interval sessions in their overall training since time immemorial. But today’s HIIT is often touted as the only exercise necessary, and not as a supplement to longer, more moderate sessions.

Does HIIT work?

“There is no question that for most people, HIIT leads to a greater increase in VO2 max” —also called maximal oxygen uptake, a measure of our aerobic capacity and endurance— “than exercise of a more moderate nature. “Said Ulrik Wisloff, professor and head of the cardiac exercise research group at the Norwegian University of Science and Technology in Trondheim, who has been studying HIIT for more than 20 years.

Higher VO2 max is highly associated with longer longevity, Wisloff added, suggesting that interval exercises are likely to have a stronger influence on our life expectancy than, for example, light walks.

HIIT can also help reduce fat stores around our midsection just as effectively as longer and easier exercises, and it seems especially beneficial for our brain.

“HIIT improves memory in young and old adults” in ways that standard moderate exercise cannot, said Jennifer Heisz, a McMaster University professor and author of the upcoming book “Move the Body, Heal the Mind.” heal the mind), which will be published in March. Only vigorous exercise causes muscles to produce a torrent of the chemical lactate, he said, which then travels through the blood to the brain, where it is known to promote the creation of new cells and blood vessels, improving brain health and reduces our risk of dementia.

The most seductive thing is that HIIT sessions can be exceptionally short. In a famous 2006 study from Gibala’s lab, for two weeks, one group of college students pedaled exercise bikes moderately for 90 to 120 minutes three times a week, while another group performed four to six training sessions. 30 seconds of intense cycling followed by four minutes of recovery. The moderate-paced athletes, who accumulated about 12 hours of exercise in total, showed improvements in fitness measures and healthy remodeling of the inner workings of their muscle fiber. But the HIIT cyclists, who completed a total of 12 minutes of intense exercise, had the same (and even better) fitness results and showed even greater molecular alterations within their muscles.

Where does HIIT fail?

“It’s not practical or advisable to do HIIT on a daily basis,” said Jamie Burr, a professor at the University of Guelph in Ontario, who has studied the physiological effects of many types of physical activity. Health guidelines generally do not advise doing this type of exercise more than three times a week, Burr said, to avoid exhaustion or injury.

But in that case, we wouldn’t be exercising for at least four days a week, which can be problematic.

“There are a number of health benefits,” most of them related to better blood sugar and blood pressure levels, he said, that occur only on days we exercise. When we skip exercise, even if we did HIIT the day before, we could lose our blood sugar and blood pressure control, undermining the long-term metabolic gains made in those previous intervals.

So if you decide to do HIIT, Burr recommends scheduling other types of exercise like walking, biking, swimming, jogging, or moderate gymnastics on most other days of the week.

Don’t get complicated. Consider the fartlek

Interested in trying HIIT? “Good,” Wisloff says. “I think everyone should aim for at least one HIIT session per week, for the sake of health.”

Choose the variety of HIIT that you like the most. You could try a minute-by-minute routine, which means you push yourself for 60 seconds, rest for the next 60 seconds, and repeat. Or the four-minute interval workouts often used in Wisloff’s research, with four minutes of strenuous exertion followed by four minutes of rest.

Other researchers apply four-second intervals. I have tried and enjoyed the 10-20-30 strategy, developed by scientists in Copenhagen, Denmark: You jog (or exercise) gently for 30 seconds, increase effort for 20 seconds, and then sprint for 10 seconds before returning to a light jog for half a minute.

But lately I’ve gotten used to frequent fartleks. Fartlek, which means “speed game” in Swedish, is a training that is based on choosing a target, such as a tree or a lamppost later in your path, and accelerating until you reach it. According to Wisloff, who also trains with fartlek, there is no need to monitor your heart rate or track the length of each interval, in time or distance. You should only use the natural elements of your environment to shape your exercise.

“This is perfect for outside of the gym,” Wisloff said, and requires little expense or experience. Just run up the tree until it’s behind you, choose another goal later, and that way you’ll hit health and fitness goals, HIIT-style. (I)