So, if you decide to do HIIT, plan to schedule other types of exercise, he said, such as moderate walking, cycling, swimming, jogging or calisthenics on most other days of the week. When we skip working out, even if we did HIIT the day before, our blood sugar and blood pressure control may slip, undercutting the long-term metabolic gains from those earlier intervals. “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 when we exercise. But the HIIT riders, who completed 12 total minutes of intense exercise, grew just as fit or fitter and showed even more molecular alterations inside their muscles.īut in that case, we are not exercising for at least four days of the week, which can be problematic. The moderate exercisers, who topped out at about 12 hours of exercise altogether, showed improved measures of fitness and healthfully remodeled the inner workings of their muscle cells. Gibala’s lab, for two weeks one group of college students pedaled stationary bicycles moderately for 90 to 120 minutes, three times a week, while another group grunted through four to six sessions of 30 seconds of all-out cycling followed by four minutes of recovery. Most beguiling, HIIT workouts can be exceptionally brief. Only strenuous exercise prompts the muscles to produce a gush of the chemical lactate, she said, which then travels through the blood to the brain, where it is known to promote the creation of new cells and blood vessels, upping brain health and lowering our risk for dementia. “HIIT improves memory in younger and older adults,” in ways that standard, moderate exercise cannot, said Jennifer Heisz, a professor at McMaster University and the author of the upcoming book “Move the Body, Heal the Mind,” which will be published in March. HIIT also may help to reduce fat stores around our midsections as effectively as longer, easier exercise, and it seems uniquely beneficial for our brains. A higher VO2max is strongly associated with greater longevity, he added, suggesting intervals are likely to have a more potent influence on our life spans than, for instance, gentle walks.

“For most people, there is no doubt that HIIT leads to larger increases in VO2max” - or maximal oxygen uptake, a measure of our aerobic fitness and endurance - “than exercise of a more moderate nature,” said Ulrik Wisloff, a 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. But today’s HIIT is often promoted as the only exercise you have to do - and not an add-on to other, longer, moderate sessions. Athletes looking for performance boosts have threaded interval sessions into their broader training since time immemorial. This exercise approach is not new, of course. It is also useful to explore the best way to do HIIT, as well as whether we need a pricey heart rate monitor, gym membership, personal trainer and advanced math skills to get started, or if sneakers, a handy hill and a distant tree can be equipment enough. With New Year’s exercise resolutions almost around the corner, now seems the right moment to home in on HIIT, and how and why to try it. Is it particularly good for our hearts? Minds? Life spans? Waistlines? Is it better for us, long term, than taking a brisk daily stroll? And what does “intense” exercise even mean?

By almost any measure, HIIT is hot.īut plenty of questions remain about HIIT. Dozens of scientific studies every month explore its benefits and drawbacks. Gym franchises and online classes specialize in HIIT. Consisting of brief spurts of intense exercise interspersed with rest, various versions of HIIT have been tested, tried, talked about and sometimes derided by countless researchers, coaches, journalists, influencers and almost anyone else interested in fitness. For the past five years or so, high-intensity interval training, or HIIT, has been one of the most popular and controversial forms of exercise.

Book brain gym