Throughout this website, you'll hear me refer to the term cardiovascular exercise or “cardio” for short.
I am using these terms interchangeably with aerobic exercise.
So, let's talk about the basics of aerobic exercise…
The word aerobic means “with oxygen.” Aerobic exercise requires oxygen.
Carbohydrates are initially used for energy during cardiovascular exercise.
Oxygen is used to break down the carbohydrates so they can be used for energy by the body. Once your carbohydrate stores are emptied, where does your body turn for energy?
Well, it really depends on the intensity of your aerobic exercise. Your body has three options for energy once the carbohydrate stores have been depleted:
- Fat for Energy
- Protein for Energy
- Fat and Protein for Energy
More than likely, a combination of fat and protein will be used for energy once your energy stores (carbs) are depleted.
Your job is to maximize the amount of fat used for fuel and minimize the amount of protein used for fuel. How do you do that?
Low intensity cardiovascular exercise shifts the energy source more towards fat. As you raise the intensity, the energy source can start to shift more towards protein for energy. You want to always focus on using fat as the energy source during cardio.
As the intensity of aerobic exercise goes up, so does the requirement for energy. So more calories are burned as the intensity is raised. As more calories are burned, you have a greater chance to burn more fat.
But, as intensity is raised the energy source is focused more towards muscle. There's a balance you must find.
Finding that Perfect Balance
You want to burn the greatest amount of fat in the shortest amount of time. So, you've got to find the perfect intensity for burning the most amount of fat in the shortest amount of time.
You don't want to be doing hours of very low intensity cardio to burn the same amount of fat in less time.
We already know that low intensity exercise uses fat solely as the energy source, but low intensity exercise must be done for very long periods of time in order to burn a substantial amount of fat.
High intensity exercise shifts the energy source more towards muscle, so we don't want to use high intensity aerobic exercise. You never want to sacrifice your hard earned muscle. It's also harder to perform high intensity exercise for long periods of time because it's so tough.
How long can you run full speed? Probably not very long unless you are a trained athlete — and even then… trained athletes can't run at full speed for very long.
If low intensity cardio takes too long to burn a substantial amount of fat and high intensity cardio uses muscle as an energy source, what does that leave?
That's right — medium intensity aerobic exercise is the perfect intensity for burning the maximum amount of fat. You can burn a ton of calories during medium intensity exercise, and you can do it for longer periods of time.
Medium intensity cardio (most of the time) will be the weapon of choice for burning fat on our programs.
Some of you that know about High Intensity Interval Training or HIIT may be wondering why I didn't choose HIIT as the best method of burning fat. You'll learn more about HIIT later — you'll see why I prefer medium intensity cardio over HIIT.
Aerobic versus Anaerobic Exercise
During aerobic exercise, energy is created through the use of oxygen. Energy for anaerobic exercise is created in the absence of oxygen. The use of oxygen to create energy is a far more efficient process than creating energy in the absence of oxygen.
The duration of aerobic exercise can last much longer due to the use of oxygen to create energy. Anaerobic exercise consists of short bursts of around 2 minutes or less due to the lack of oxygen in creating energy to sustain the process.
So, activities such as weight lifting and sprinting are classified as anaerobic while activities performed for longer durations such as jogging, cycling, and swimming are classified as anaerobic.
Sports such as football, baseball, and basketball are neither aerobic nor anaerobic in their entirety. They are a combination of the two types…
Think about the sport of soccer for a second. There are periods of low intensity followed by bursts of all out high intensity.
So, for fat burning purposes, sports and other anaerobic activities are not the best choice.
You'll want to stick with continuous activities that do not have rest periods. This forces the body to use oxygen to create energy and therefore burn fat as an energy source.