HIIT: High Intensity Interval Training


by Sara Thompson and Fiona Callender

This summer, Fiona and I travelled to various labs around the world. We targeted exercise physiologists in particular who are the leading researchers in the area of high-intensity exercise in the aging population. We hoped to learn more about their research and discuss what they think the future is for this field. It was great to be able to meet with these researchers in their setting as we were welcomed into their lab space and even witnessed some of the studies being done! The first stop was at the University of British Columbia Kelowna campus, where I might with Dr. Jonathan Little and his team of graduate students. 


Dr. Little specializes in high intensity interval training (HIIT) in adults with type 2 diabetes (T2D). T2D is characterized by insulin resistance and high blood glucose levels, and is often associated with cardiovascular disease, kidney disease, neuropathy and retinopathy (Sheetz & King, 2002). We were particularly interested in discussing his research as T2D affects 387 million people worldwide and is a major health issue in the aging population (International Diabetes Federation, 2014). In addition to the health concerns involved in T2D, in 2014 the costs associated with this disease alone were $612 USD (International Diabetes Federation, 2014). Finding a cost-effective treatment or preventative solution is vitally important, and Dr. Little is finding that exercise does just that!

I sat down with Dr. Little and our very own FTG writer Julianne Barry, who is the lead on many of the studies carried out in the lab. They were both keen to discuss their current research and future investigations. It has been accepted for some time that aerobic, moderate-intensity exercise improves insulin function in T2D; however, getting individuals with T2D to adhere to an exercise program is challenging. HIIT might be a solution to this problem. As discussed in previous FTG articles, HIIT consists of exercise in which the individual does several bursts of intense exercise, with rest periods in between. This type of training has received a lot of media attention in the past decade as a possible solution to the main limiting factor for individuals trying to exercise – lack of time. Fascinatingly, HIIT has been shown to elicit the same (or greater) health benefits as traditional endurance training (e.g. walking, jogging, swimming) with considerably less time involved. However, where does T2D fit into this equation?

One of the main concerns about HIIT is that most people perceive it to be fine for a young and healthy population but find it unrealistic to consider for compromised populations due to its very intense nature. Therefore, Dr. Little’s team focuses on what’s called the “practical HIIT” model, or one that is more conducive to individuals who are older, have medical conditions, or are unaccustomed to exercise. This model consists of 10 repetitions of 1-minute exercise at around 90% of maximal capacity, interspersed with 1-minute of rest. In this way, individuals with T2D are able to complete this type of high-intensity exercise, and it has been shown to improve postprandial glycemic control in this population (Little et al., 2004).

One of the most fascinating aspects of these studies is that individuals are given instructions on how to perform exercise on their own. Another negative conception of HIIT is that while it is a very potent training stimulus, it’s hard to manage this type of training outside of a lab. To combat this problem, individuals in these studies were counseled on what “zone” to be in, or how to gauge their effort while they exercise. This involved taking the participants outside and showing them the proper walking/running speed to go at in order to reach 90% of their maximal capacity. Importantly, participants were encouraged to choose an activity that they would be able to stick with outside of the lab. The majority of participants chose to perform their HIIT workouts by speed walking up hills, making it accessible to individuals who don’t have access to a gym or workout equipment.

When I asked if there were any major research surprises when conducting these studies, Dr. Little said that most participants really enjoy it, and that there is often friendly competition amongst participants! In fact, Dr. Little’s lab executed a study on the enjoyment of this type of exercise. While participants rated HIIT to be slightly less enjoyable than continuous moderate intensity, individuals preferred to perform HIIT to any other type of exercise. This could be because as the workout is broken up into small bursts, individuals have a continuous feeling of accomplishment throughout the workout (Jung et al., 2014). Julianne Barry discusses this study in further detail (hyperlink to Julianne’s FTG article). This is significant, as the most important factor is not WHAT exercise individuals are doing, but whether or not they enjoy it enough to stick with it. Indeed, Little discussed that individuals performing HIIT have better adherence after one month compared to endurance training!

As with any study, Dr. Little ensured that the participants were deemed safe to perform exercise, and avoided recruiting individuals with a history of cardiac event. However, Little states that the main message they want to spread is that while this type of exercise is often referred to as “high intensity” or “sprint training”, this doesn’t mean that they’re having individuals with T2D who have no prior exercise experience, go out and run sprints. For these individuals, they have found that just walking up a hill is at 90% of their maximal capacity (and enough of a training stimulus to elicit health benefits!). For these patients, any exercise they do HAS to be HIIT – they’re just facilitating the training and monitoring their progression.

As we have learned throughout our travels to various research labs, there is no gold standard HIIT protocol. The practical HIIT model performed by Dr. Little’s lab appears to be practical, safe, time efficient and, most importantly, fun for T2D patients! In addition to improved insulin function, one of the most promising findings is that individuals FEEL better. Dr. Little shared that at the beginning of a study, one participant had to take four breaks in order to make it up the stairs to the parking lot. However by the end of the study, this participant was able to climb the stairs without taking a break. Imagine how this must have improved her functional ability and quality of life!

My visit to the University of British Columbia was fascinating and I’m looking forward to learning further about HIIT for T2D. I will keep you posted on future studies by this incredible team!


Sheetz, M. J., & King, G. L. (2002). Molecular understanding of hyperglycemia’s adverse effects for diabetic complications. Journal of the American Medical Association, 288, 2579–2588.

International Diabetes Federation. (2014). IDF diabetes atlas (6th ed.). Brussels, Belgium: International Diabetes Federation Retrieved from http://www.idf.org/diabetesatlas

Little JP*, Jung ME, Wright AE, Wright W, Manders RJF (2014). Effects of high-intensity interval exercise versus continuous-moderate intensity exercise on postprandial glycemic control assessed by continuous glucose monitoring in obese adults.

Jung ME, Bourne JE, Little JP. (2014). Where does HIT Fit? An examination of the affective response to high-intensity intervals in comparison to continuous moredrate- and continuous vigorous-intensity exercise in the exercise intensity/-affect continuum.

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