The basic science behind this is that it takes more oxygen to burn 1 calorie from fat than it takes to burn 1 calorie from carbohydrate, so as your body begins to work harder and get lower on oxygen, it turns more to carbohydrate as an energy source.
When it comes to cardio, the question I probably receive most is: long and slow or short and fast? This question actually reflects the most important concept behind a good cardio routine. The truth is, it depends. Let’s begin by looking at total amount of calories burnt.
Say I ask you to travel a mile on foot. I don’t care how you do it – walk, jog, or run. Many exercise professionals will tell you that you’ll burn the same number of calories any way you do it, as long as you’re covering the same distance. This is simply not true. Studies have shown that the faster you cover that distance, the more calories you burn, period. There is a higher metabolic cost to moving quickly than to moving slowly. So you’re going to burn the most calories by pedaling, running, rowing, swimming, or doing any other cardio you do as fast as possible. The added bonus is that the faster you move, the higher your post-exercise metabolism becomes, meaning that you burn more calories throughout the day after your workout than if you had moved at a slower pace.
Let’s finish with a sample workout that will keep you in both zones during the same workout. This is an “interval” routine. Here’s how it works:
- 5 minute graded warm-up, gradually working up to a hard intensity by minute 5
- 1 minute hard-fast effort (labored breathing)
- 2 minutes easy-medium effort (conversation possible)
- 2 minutes hard-fast effort
- 1 minute easy-medium effort
- repeat 1x
- 3 minutes hard-fast effort
- 3 minutes easy-medium effort
- 4 minutes hard-fast effort
- 4 minutes easy-medium effort
- repeat 1x
- 5 minute cool-down, gradually working down to a very easy effort by minute 5.