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Are Shorter HIIT Workouts More Effective Than Longer HIIT Workouts?

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Conventional wisdom says that the more time you spend exercising, the fitter you'll become (with the exception of overtraining). But according to a new study published in Medicine & Science in Sports & Exercise, that might not *always* be the case. Sure, if you spend hours every week logging miles on the treadmill, you're going to increase your endurance. And if you work hard on your deadlift a few times per week, your PR will probably go up. But when it comes to HIIT, less might actually be more. ~Squat jumps for joy.~

The authors of the study started by looking for other research that has been done recently on sprint interval training, where people engaged in very high-intensity exercise interspersed with periods of rest. This kind of physical training relies heavily on the concept of VO2 max, which is a number that indicates the amount of oxygen your body is able to use during exercise. The higher your number is, the more fit you are, so it's a great benchmark of how much progress someone has made through exercise, as well as how hard you're working during the actual workout. Researchers concluded that doing a smaller number of interval sets did not hinder people's ability to improve their VO2 max. In fact, each additional sprint interval after two sets actually reduced their increase in VO2 max by 5 percent.

Why would doing more sets mean a worse result? The authors think the process by which VO2 max improves might be completed within two sprints, meaning that further work doesn't have any additional benefit. Or, it could be that people pace themselves differently after the second set.

Important to note: The intervals evaluated in this study were conducted with special bicycles that allowed people do "supramaximal" sprints, or efforts that were at a level above their VO2 max. "Supramaximal sprints are sprints at the highest achievable intensity for an individual," explains Niels Vollaard, Ph.D., lead author of the study. "This is not something only athletes or very fit people can do; everyone can achieve their own best effort," he continues, although it's not recommended for those with uncontrolled high blood pressure. While this kind of exercise has the benefit of being physically accessible for everyone, a regular gym bike or other common equipment, unfortunately, won't work for reaching this intense level of effort, making it difficult to replicate this effect at home. "It is possible to do this without equipment by running up stairs or up a steep hill, but we don't recommend this because of the increased risk of injury," he says.

So what's the bottom line here? "People who don't exercise because of lack of time can still reap the health benefits of exercise by performing short training sessions involving intense sprints." (See: The Workout Excuse the Tone It Up Girls Want You to Stop Making) And the bikes used in the study recently became commercially available, opening up a whole new area of possibility. "We are currently applying for research funding to investigate this type of exercise as a workplace-based exercise routine," says Vollaard. "By making these bikes available in the workplace, we could potentially remove a lot of the barriers that prevent many people from doing enough exercise."

For now, this research serves as a reminder that you don't need a ton of time to score a solid workout. After all, there's ample proof that any exercise is better than no exercise, so if you're pressed for time, even a short workout will pay off.

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