Dr. Kyle: High Intensity Interval Training!

I’m sure you’ve heard the hype about high intensity interval training (HIIT) – bursts of exertion separated by short periods of recovery – sound tough, right? That’s because it is. The attention around HIIT has provoked researchers to further investigate it’s physiological benefits, which have been promising.

The problem with most workout programs is lack of intensity. People putt around the gym for about an hour, jump from one machine to the next without breaking a sweat. What’s the problem? Nothing, if your goal is to build strength. But from a physical fitness and weight loss perspective, you are overlooking HIIT’s cardiovascular and fat-incinerating benefits.

HIIT is a time-efficient strategy to increase muscle and accelerate fat loss. Intervals of activity and rest can vary between 30 seconds to a few minutes. The duration and intervals can be modified depending on the individual and goal in mind. The objective is to create a fast-paced and physically demanding workout that challenges our threshold of exercise intensity.

So why HIIT vs. cardio?

HIIT is most commonly compared to moderate intensity continuous training (MICT). MICT, also known as steady state cardio, consists of long periods of activity at constant intensity. For example, 45 minutes of jogging at 5km/h is considered MICT. Although it provides significant cardiovascular improvements and may be a favourite for endurance training, HIIT can offer more!! Remember, you can’t go wrong with increasing the intensity of exercise. Let’s compare!

With regards to that pesky body fat, HIIT significantly reduces abdominal and visceral fat in both men and women (1). High intensity training, above 90% peak heart rate, was more effective at reducing whole-body adipose tissue. Many studies show HIIT is superior to MICT in improving aerobic fitness (2). Cardiovascular measures (VO2 max, contractile function, ejection fraction, respiratory fitness and endothelial function) significantly improved with 7-12-week HIIT programs. This holds true for people who have previously suffered from a cardiac incident. Implementing HIIT under supervision during cardiac rehabilitation can improve quality of life by enhancing their cardiorespiratory fitness. No deaths or cardiac events occurred during HIIT programs across all recent studies. What doesn’t kill you makes you stronger, right?

Additionally, studies have demonstrated greater improvements in insulin sensitivity, glucose regulation, HDL cholesterol, and blood pressure with HIIT compared to MICT (2,3). Improved insulin sensitivity allows the body to utilize glucose more efficiently as energy, instead of being stored as fat! By implementing HIIT with intermittent fasting, the body utilizes fat stores for energy, increasing fat oxidation and mobilization (4). HIIT is also more effective than MICT at reducing oxidative stress and inflammation (5). These benefits are observed in subjects across all age categories. HIIT doesn’t discriminate; all can experience the health advantages of HIIT.

HIIT is extremely efficient because we experience what’s known as “excess post-exercise oxygen consumption,” or EPOC – meaning we reap the calorie-burning effects hours after our workout.

During intensive exercise, energy stores are quickly depleted. Our carbohydrate stores, oxygen and other essential compounds are exhausted, resulting in an energy deficit. After HIIT, we eventually reach our normal resting level of metabolic function. Carb stores are replaced (with an appropriate diet), oxygen levels will increase, and body temperature will return to normal (6). These processes require energy, explaining why we continue to burn calories after exercise. Even though HIIT and MICT both induce EPOC, HITT increases lipid metabolism to a greater extent AND is extremely time efficient (6).

So whether you want to call it HIIT, interval training, circuit training, etc., say hello to the most time efficient and beneficial exercise available. Combining HIIT with intermittent fasting and a wholesome diet, expect accelerated fat loss and physical fitness improvements. So what are you waiting for? Let’s turn up the intensity to 11!

References:

1. Maillard F, Pereira B, Boisseau N. Effect of high-intensity interval training on total, abdominal and visceral fat mass: a meta-analysis. Sports Medicine. 2018 Feb 1;48(2):269-88.

2. Hannan AL, Hing W, Simas V, Climstein M, Coombes JS, Jayasinghe R, Byrnes J, Furness J. High-intensity interval training versus moderate-intensity continuous training within cardiac rehabilitation: a systematic review and meta-analysis. Open access journal of sports medicine. 2018;9:1.

3. Costa EC, Hay JL, Kehler DS, Boreskie KF, Arora RC, Umpierre D, Szwajcer A, Duhamel TA. Effects of high-intensity interval training versus moderate-intensity continuous training on blood pressure in adults with pre-to established hypertension: A systematic review and meta-analysis of randomized trials. Sports Medicine. 2018 Sep 1;48(9):2127-42.

4. Wilson RA, Deasy W, Stathis C, Hayes A, Cooke M. Combining intermittent fasting with high intensity interval training reduces fat mass by increasing fat oxidation and mobilization. InAustralia and New Zealand Obesity Society and Breakthrough Discoveries 2018 Joint Conference, Melbourne, Australia, 16-18 October 2018. 2018

5. Ramos, Joyce S., et al. “The impact of high-intensity interval training versus moderate-intensity continuous training on vascular function: a systematic review and meta-analysis.” Sports medicine 45.5 (2015): 679-692.

6. Ahlert M, Matzenbacher F, Albarello JC, Halmenschlager GH. Comparison of epoc and recovery energy expenditure between hiit and continuous aerobic exercise training. Revista Brasileira de Medicina do Esporte. 2019 Feb;25(1):20-3.