by: Victoria Frosini, MS, CPT

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She earned her Master’s of Science degree in Nutrition and Dietetics in 2013, where she conducted extensive research in weight loss, social support and cognitive behavioral therapy.

Why HIIT Works

Time is the number one reason people struggle to exercise. It can be challenging to implement and stick to a routine when we’re busy juggling work, school, relationships and family. What if you could do less and still see results? Here’s a deep dive into how HIIT can give maximal results on minimal time!

Breaking down HIIT basics

In order to see results from your fitness program, your body must undergo stress followed by metabolic and physiological adaptations. High intensity interval training or (HIIT) is characterized by short, intermittent bursts of vigorous exercise, combined with periods of rest. The appeal of this approach is pretty straightforward. Exercise sessions can be short and effective, making your time commitment less and your fitness adaptations greater. As an added bonus, when you finish a HIIT workout, your body continues to burn calories while simultaneously increasing muscle building signals.

What types of exercise count?

HIIT is extremely versatile. In fact, it can be applied to nearly any exercise modality from the comforts of your own home! Bike, sprint, jump, or complete body weight movements until failure. As long as you’re breathing hard and your muscles are burning, you’re doing it right.

What qualifies as vigorous intensity?

The main purpose of HIIT is to push your body beyond its comfort zone. The ideal interval should be at the top of the intensity range (for example an 8 or 9 on a 1-10 RPE scale). If you are doing HIIT right, your body requires recovery following the work period. How do you know if your effort is enough? We suggest using the “talk test” to determine if your intensity is appropriate. Here’s a tip. If you can chat with a friend you’re most likely missing the benefits of high intensity exercise. In a maximum effort, you won’t be able to say more than a few words before you are breathless. 

The science behind high intensity

High intensity intervals have been shown to improve both aerobic (with oxygen) and anaerobic (without oxygen) exercise ability. The benefits of HIIT include significant improvements in functional exercise performance, skeletal muscle mitochondrial adaptation, and acute heart rate recovery. In addition, several studies have illustrated HIIT can improve body composition through the reduction of abdominal and visceral fat while simultaneously building lean body mass. Need more motivation for HIIT? Studies show intense exercise reduces all out mortality risk compared to moderate intensity exercise alone. 

We suggest 1-3 HIIT sessions per week to avoid burnout and injuries. 




Connolly, L. J., Bailey, S. J., Krustrup, P., Fulford, J., Smietanka, C., & Jones, A. M. (2017). Effects of self-paced interval and continuous training on health markers in women. European Journal of Applied Physiology, 117(11), 2281–2293.

Foster, C., Farland, C. V., Guidotti, F., Harbin, M., Roberts, B., Schuette, J., … Porcari, J. P. (2015). The Effects of High Intensity Interval Training vs Steady State Training on Aerobic and Anaerobic Capacity. Journal of Sports Science & Medicine, 14(4), 747–755.

Heydari, M., Freund, J., & Boutcher, S. H. (2012). The Effect of High-Intensity Intermittent Exercise on Body Composition of Overweight Young Males. Journal of Obesity, 2012, 480467.

Knowles, A.-M., Herbert, P., Easton, C., Sculthorpe, N., & Grace, F. M. (2015). Impact of low-volume, high-intensity interval training on maximal aerobic capacity, health-related quality of life and motivation to exercise in ageing men.

Little, J. P., Safdar, A., Wilkin, G. P., Tarnopolsky, M. A. and Gibala, M. J. (2010), A practical model of low-volume high-intensity interval training induces mitochondrial biogenesis in human skeletal muscle: potential mechanisms. The Journal of Physiology, 588: 1011–1022.

Sculthorpe, N. F., Herbert, P., & Grace, F. (2017). One session of high-intensity interval training (HIIT) every 5 days, improves muscle power but not static balance in lifelong sedentary ageing men: A randomized controlled trial. Medicine, 96(6), e6040.

Shen Y, Huang G, McCormick BP, Song T, Xu X (2017). Effects of high-intensity interval versus mild-intensity endurance training on metabolic phenotype and corticosterone response in rats fed a high-fat or control diet. PLOS ONE 12(7): e0181684.

Stöggl, T. L., & Björklund, G. (2017). High Intensity Interval Training Leads to Greater Improvements in Acute Heart Rate Recovery and Anaerobic Power as High Volume Low Intensity Training. Frontiers in Physiology, 8, 562.

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