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HIIT has been called the closest thing to an exercise pill.

While it might take a bit more effort, there is now no doubt at all that high-intensity interval training is just what the doctor ordered.

Anyone who follows the latest in fitness news knows that HIIT is a hit. A big hit. But high-intensity interval training is much more than a fad – it is a scientifically proven way to build cardiovascular fitness, and research is revealing plenty more health benefits it can bestow. Here are five of the top researched reasons to put HIIT on your own workout list:

  • HIIT improves lean body mass and maximal oxygen consumption, while drastically cutting the risk of heart disease. Learn more.
  • HIIT is extremely effective at cutting stubborn and unhealthy tummy fat. Learn more.
  • In both young (18 to 30) and older (65 to 80) exercisers, a major study showed HIIT had by far the greatest activation of muscle and fat-burning capacity, when compared with other types of exercise. Learn more.
  • HIIT has been shown to be much better than other workouts for producing excess post-exercise oxygen consumption (EPOC), meaning your body continues to use oxygen and burn fat long after you’ve stopped exercising. Learn more.
  • HIIT has been shown to be more enjoyable – in one study 92 percent of participants favored a HIIT workout over traditional moderate continuous exercise. Learn more.

So, the research definitely supports HIIT. But what about the science that goes into actually designing an effective HIIT program? LES MILLS GRIT is designed to push the heart rate up as high as possible, as often as possible in a 30 minute phase. The workout is designed to have these very high spikes of intensity, followed by a complete recovery. And it’s those spikes that generate the types of biochemical changes that are very specific to a HIIT workout. The workout is then tested by a team led by Dr. Jinger Gottschall of Penn State University to measure its efficacy, and only then made available.

This piece originally appeared on

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Bryce Hastings
Bryce Hastings is the Group Fitness Research and Operations Manager for Les Mills International. Literally the brains behind the brawn, he leads groundbreaking research and collaborates with internationally-renown research partners to unearth the latest and most effective fitness techniques. Hastings became a certified Physical Therapist in 1986 and completed his Advanced Diploma in Manipulative Therapy at AUT University Auckland in 1990. He serves as a Research Associate at Auckland University of Technology and has been lecturing part time there for the last eight years. In 1990, Bryce opened his private physical therapy practice at Les Mills World of Fitness in Auckland, the original Les Mills gym established in 1968 by Les Mills Senior.