Low Intensity vs. High Intensity Cardio – Part II

A couple of weeks back we discussed the notion of high intensity cardio workouts versus lower intensity cardio workouts. As I finished that article, it is critical for people to understand there is a place for both types of exercise. Consider that for years continuous, moderate intensity work was used (and still should be used) for the wide array of health benefits derived from exercise. Reductions in blood pressure, cholesterol, insulin resistance and body fat are all commonplace. People certainly didn’t get fat doing cardio so don’t buy into that line of thinking. They may not have optimized their fat burning environment, but that is all they would be guilty of.

I wanted to put some numbers together for those of you who might be more of a believer to “see it for yourself”. Fortunately these scenarios work equally well for both men and women so we will use a female as an example. The “old fashioned” way of burning fat during your cardio was to really dial it down, say 45-50% of your maximal level, for at least 60 minutes. Thus, a 150-pound female with an average fitness level might walk at around 3 mph at 5% grade and would burn around 5 – 6 calories per minute for a total of 300 – 360 calories for the 60-minute workout. It is reasonable to assume she would burn around 60% of her calories from fat, meaning 180 – 216 of the calories she burned were burned as fat.

In the other scenario if the same woman jogged for one minute at 80% of her maximum and then walked for one minute at 40% of her maximum and did this for the same amount of time, she would conceivably “average” a higher intensity. For starters this would certainly burn more calories on the front end (because she is exercising harder). Now during the first workout she would likely burn a higher percentage of calories from fat, but this higher percentage is largely made up for by the fact that she is working harder and burning more calories overall.

In closing, the big selling points for higher intensity work are three-fold:

1. Efficiency
2. Fitness improvements
3. EPOC

The #1 complaint or barrier for non-exercisers is a lack of time, so getting in simple and effective interval workouts help to overcome this as a problem. Next, working harder and doing so over longer and longer periods of time will work wonders to improve your overall fitness. With a higher fitness level, hard workouts become easier and you are more apt to exercise for a longer period of time; both of which translate into greater fitness and more calorie burning. Finally, EPOC stands for excess post-exercise oxygen consumption. It is the primary physiological concept for doing resistance training work as well as higher intensity work. In essence, achieving a greater EPOC results in more calorie burning during recovery from your workouts or when you are sitting on the couch or at your desk. Since recovery is fueled at rest and fat burning predominates at rest (albeit at a very slow rate), a greater EPOC from higher intensity work in theory will promote more fat burning across the day.

As usual I will close with being practical. The best cardio is what you will do and what type of cardio is most enjoyable to you. If you like walking slower at an incline while watching TV then go for it, I will ask you to crank up the speed a couple of ticks and increase the incline 1 – 2 %. If you want to do intervals because it’s all the rage, then dominate it. The biggest thing is to push it. If you’re going to push away life to get to the gym, then I beg and plead with you to work as hard as your current fitness allows.

This post was written by Chad Kerksick, an Assistant Professor of Exercise Science at Lindenwood University in St. Charles, MO. Dr. Kerksick is a nerd for exercise physiology and particularly enjoys discussing strategies to lose fat and enhance performance through diet, supplementation and exercise.

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