by Krista Henderson

This month, I want to teach you the difference between aerobic vs. anaerobic exercise zones, including when to use them, how to determine which zone you are in and clear up the biggest myth regarding The Fat Burning Zone.

Aerobic Training

The word "aerobic" means "with oxygen".  Oxygen is required to move your large muscles (i.e. quadriceps in your legs) in an exercise motion for a significant period of time.  The majority of people's daily exercise should occur aerobically; therefore it's important to understand its properties.

When you are in an aerobic state, the body's primary sources of fuel are fat and carbohydrates (glucose).  As your exercise intensity increases, your body starts to use more carbohydrates, and less fat.  Fitness improvements are achieved by sustaining higher intensity levels, yet still within the aerobic zone.  And if you want to maximize your calorie burn, a higher intensity level will provide that - it doesn't matter if you burn fat calories or carbohydrate calories, what matters is the total amount of calories.

What is a high-intensity aerobic workout?

Remaining aerobic means working at 80% or less of your maximum heart rate (MHR).  One way to measure this intensity is by using a 1-10 scale system known as the Rate of Perceived Exertion (RPE).  This scale is based on a percentage of your maximum heart rate (a topic that will be discussed in an upcoming article).

A high-intensity aerobic workout occurs at a level of 7-8, which equates to 70-80% maximum heart rate.

What does a level 7-8 feel like?

7 or 70% of MHR - this is the feeling you get when exercising vigorously; you definitely feel fatigued but are confident you can maintain this for your entire cardio session. You can carry on a conversation, but prefer not to.

8 (80% of MHR): this is the feeling you get when exercising very vigorously; you think you can hold this level for your whole cardio session, but are no 100% sure. Breathing is very deep, you can talk but don't feel like it.  You should experience this feeling only when you can comfortably hold a level 7 work out.