Like most other forms of exercise, particularly cardio, HIIT is effective, but it is also just a tool to utilize as needed.
What Makes HIIT Effective
The major draw to HIIT cardio is you are burning as many calories as a 45 minute moderate intensity cardio session. So it is great for saving time if you don’t want to spend 45 minutes in the gym. The other benefit is the intensity itself. As with many things in life, we have different personality types. The majority of people I see doing HIIT are people who love that fast paced, hardcore mentality. They want to be out of breath covered in sweat when they are done. This provides a quick, efficient option for burning calories.
Why It’s Just a Tool
The reason I say it is just a tool is because your body can only handle so much. A big issue I have had with clients is they start with 2 days a week. Then they think “more is better” so eventually they work themselves up to 5-6 days a week. The reality of this situation is HIIT cardio is very taxing on your central nervous system when done correctly. If you are doing too much of it, your body will have a hard time recovering. It will also send your cortisol levels through the roof, and keep them that way if you aren’t giving yourself enough time off.
Don’t be fooled by the fact that it’s short. The reason it burns as many calories in as little of a time frame is because of how intense it is. If you decide to incorporate HIIT into your workout regimen, do not add more than 2-3 days a week. This is especially true if you are already lifting weights 2-3 times a week. As a side note, I would like to place emphasis on the fact that you should be focusing on lifting weights before adding in any cardio. Let’s not forget over a long enough timeline, your body burns less calories doing the same cardio bout, which means you’d need to keep upping the session to achieve the same result.
Lifting weights, on the other hand, does the opposite. The more muscle you have on your frame, the more calories you burn at rest.
How to Incorporate HIIT Sessions
This is a general recommendation and ideally, some experimentation would need to be done on your part to figure out the best setup for YOU. Having said that, if you are trying to include some cardio on top of your 2-3 lifting days I would generally suggest:
If you are of the personality that likes intensity – 2 days to start. Only add a 3rd if you feel you have plateaued using only 2 days. These sessions shouldn’t exceed 20-30 minutes. The sprints themselves should be ALL out efforts. That’s the only way these will be effective. If you are only going 70-80% max effort, then it is not HIIT. Use the 1-1.5 minute steady state jogs in between to recover and bring your heart rate down for the next bout.
If you are of the personality that prefers lower intensity – You may not even need HIIT. Start with 2-3 days of 25-30 minute steady state jogging sessions. If you can’t hit your goals with that, and want to mix it up, feel free to replace one of the three sessions with HIIT and maybe add another along the way. There is no rule saying you HAVE to do this though, it is all a matter of preference.