Though the idea of interval-type exercise has been around for more than a half a century and has helped countless athletes achieve record performance, the last decade has witnessed an explosion of interest by researchers and excitement for individuals aiming to get in better shape.

The recent enthusiasm for interval-based exercise can be traced to research from Canada and Europe in the early 2000s. The research in Canada started with exercise protocols that required participants to pedal at an all-out intensity for 30 seconds before recovering for a few minutes and then doing it again and again several more times. In contrast, the European research utilized relatively long but less intense intervals in cardiac patients. Findings from these studies demonstrated that interval-based exercise is a powerful tool for improving exercise performance and health.

The workout by any other name would still be effective

This form of training is so flexible that it has produced an endless number of training options and several different names to describe it. High-intensity interval training (or HIIT or HIT) is likely the most common name but several other labels exist as well, including sprint interval training (or SIT) or high-intensity interval exercise (or HIIE).

One other aspect of flexibility around HIIT relates to the style of exercise. Most of the original HIIT workouts focused on what many call “cardio HIIT” in that it utilizes traditional cardio-based exercise options such as running and cycling. However, much of the contemporary use of HIIT is perhaps best described as “body weight HIIT” and includes some combination of resistance exercise and calisthenics. Most of the research to date is based on cardio types of HIIT but all signs point towards both forms of HIIT being highly beneficial. 

Get your motor running

The important idea behind all forms of HIIT is providing an intense phase of exercise followed by a period of recovery. Each phase can range from a few seconds to a few minutes and are conducted across a range of intensities. The number of ways that HIIT can be configured is almost too numerous to count and perhaps this multitude of options is one of the reasons that so many people across a wide range of age, fitness and exercise experience seem to prefer this form of exercise over continuous exercise. Though planning and implementing HIIT is somewhat more complex than continuous exercise, its flexibility makes it a very attractive option for both new exercisers and the hardcore fitness junkie.

One important consideration around HIIT is that it provides the exerciser the opportunity to experience the extra benefits of intense exercise without creating an experience that is negative or unpleasant. While there is no magic recipe for creating the perfect HIIT experience, research suggests that a good approach is to avoid the combination of work intervals that are both long and extremely intense. Longer intervals should be paired with high intensities, while shorter intervals can be paired with very high intensities.

Exercisers should seek to create a HIIT experience that provides a great workout while simultaneously building confidence and producing positive attitudes and emotions.

HIIT is an approach to exercise that provides a great opportunity to boost health and fitness in a variety of populations. All that is needed is a bit of patience in finding the right style and approach to HIIT and a willingness to try new versions and variations to keep things fresh and interesting. 

HIIT has been named the #1 Fitness Trend for 2018 via ACSM's Worldwide Survey. To learn about the other trends, check out this article in ACSM's Health & Fitness Journal. 




Dr. Marcus Kilpatrick earned his bachelor’s degree from Florida State University in 1994, his master’s and doctoral degrees from the University of Texas at Austin in 1996 and 1999. He joined the faculty at USF in 2004 after spending five years at Southeastern Louisiana University in Hammond, Louisiana. Dr. Kilpatrick’s teaching efforts are linked to the undergraduate and graduate Exercise Science programs. His teaching experiences and responsibilities are varied but primarily focus on sport and exercise psychology, exercise testing and prescription, and research methods.