5 Benefits of High-Intensity Interval Training (HIIT)
Recently there has been somewhat of a paradigm shift in what people believe is the most optimal intensity to perform cardiovascular exercise at—that being the shift from (LISS) low intensity, steady-state cardio (e.g. walking) to high-intensity interval training (e.g. running sprints). While the debate of which of these types of cardio is superior for fat loss extends beyond the scope of this article, it is pertinent to consider the major benefits of HIIT.
What is HIIT?
HIIT is basically any form of cardiovascular exercise when you push yourself as hard as you can go until exhaustion kicks in (i.e. sprint for 15-20 seconds). This forces your body to rely on anaerobic metabolism (since oxygen is depleted) and you start to tax a variety of energy systems in the body. In turn, HIIT elicits a variety of metabolic adaptations that traditional LISS cardio does not.
Here’s an example High-Intensity Interval Training (HIIT) routine:
-Warm up with 5-10 minutes of light jogging
-Sprint for 15-20 seconds
-Walk for 60-90 seconds until you are fully recovered
-Repeat 5-10 times (aim to improve your capacity over time)
Most traditional fitness wisdom would suggest that LISS cardio is the better option for weight loss since it burns more “fat for fuel” than HIIT which is predominantly glycolytic (i.e. uses carbohydrates for energy). However, this is a shortsighted theory and has little conclusive literature to support its position. In fact, HIIT cardio appears to not only burn more fat (in the long run) but also enhances muscle gain in active individuals. 
There are a myriad of physiological effects that HIIT stimulates that typical LISS cardio does not. Studies consistently find that the metabolic adaptations incurred by HIIT, such as excess post-exercise oxygen uptake (EPOC), endocrine activity, blood lipids, heart function, etc. are much more pronounced than those established from LISS cardio. [2, 3]
What this means, essentially, is that while LISS cardio may burn more percentage of the calories from fat during the actual training session, its metabolic benefits are rather acute and don’t extend nearly as far as HIIT does. With LISS cardio, you’re basically playing the calories in vs. calories out game, whereas HIIT is more analogous to actually putting your body through a resistance training session.
In fact, research suggests that doing a few HIIT sessions per week (and watching your diet) can even help prevent/reverse type-2 diabetes.  Intuitively then, you can see why HIIT would be preferable for someone looking to be healthy and lean.
Moreover, HIIT is the best way to shed fat and keep it off.  This appears to be because HIIT stimulates a process in cells called mitochondrial biogenesis. The reason that process is so crucial is because it increases metabolism—your body essentially requires more energy to perform daily functions.
So let’s recap the top 5 benefits of HIIT:
- Promotes sustainable fat loss
- Improves insulin sensitivity
- Increases resting metabolic rate
- Improves cholesterol levels and blood pressure
- Helps keep your heart healthy
Now don’t get too ahead of yourself just yet and assume that HIIT should be the only form of cardio you do for the rest of your life. LISS cardio still has its place in most anyone’s fitness regimen, but HIIT should take precedence over it. Start by incorporating at least 2-3 HIIT sessions every week. Be sure to continually push yourself further/harder when you do HIIT since your body will eventually adapt and need more of a challenge than it’s used to.
Hopefully you will find the benefits of HIIT well worth the effort; you reap what you sow!
- Davis, W. J., Wood, D. T., Andrews, R. G., Elkind, L. M., & Davis, W. B. (2008). Concurrent training enhances athletes’ strength, muscle endurance, and other measures.The Journal of Strength & Conditioning Research, 22(5), 1487-1502.
- Laursen, P. B., & Jenkins, D. G. (2002). The scientific basis for high-intensity interval training.Sports Medicine, 32(1), 53-73.
- Wisløff, U., Støylen, A., Loennechen, J. P., Bruvold, M., Rognmo, Ø., Haram, P. M., … & Skjærpe, T. (2007). Superior cardiovascular effect of aerobic interval training versus moderate continuous training in heart failure patients a randomized study.Circulation, 115(24), 3086-3094.
- Mendes, R., Sousa, N., Garrido, N., Rocha, P., José, L. T. B., & Victor, M. R. (2013). EFFICACY OF ACUTE HIGH-INTENSITY INTERVAL TRAINING IN LOWERING GLYCEMIA IN PATIENTS WITH TYPE 2 DIABETES: DIABETES EM MOVIMENTO® PILOT STUDY. British journal of sports medicine, 47(10), e3-e3.
- Gibala, M. J., & McGee, S. L. (2008). Metabolic adaptations to short-term high-intensity interval training: a little pain for a lot of gain?. Exercise and sport sciences reviews, 36(2), 58-63.