If you have ever done any type of endurance cardiovascular training, you are probably familiar with “the wall”. In a nutshell, it is the point at which your body runs out of easily assessable carbohydrate energy to power your workout, and you just flat run out of steam.

Well, if you don’t know what you are doing, this can either be the end of your workout, or it can be a very damage-inducing physiological state if you don’t handle it properly. However, if you are familiar with what it all means, not only can you keep your training going, but you can burn through a very high level of bodyfat at the same time!

Energy Sources

There are 3 macronutrients that we ingest into the human body, and each one of them can be broken down and used for energy during exercise. They are Fat, Protein, and Carbohydrates.

Fat is the most energy-dense of the macronutrients, having 9 calories per gram, while both Protein and Carbohydrates only have 4 calories per gram. When doing cardiovascular exercise, your body can use all 3 of these sources of energy, depending on various factors.

Using Energy for Cardiovascular Exercise

Generally speaking, your body always finds the fastest and easiest route to find energy to power your workout. Although it may not feel like it sometimes, your body is an incredibly efficient machine and it always knows the best way to attain the energy that is needed.

Initially your body wants to go after energy that has not yet been stored, and that is still being processed. Any calories that you have taken in within an hour or two before working out will fall into this category.

Next up, your body will go after energy that is stored, but that it can get to easily, which includes both carbohydrate energy stored in your muscles in a form called Glycogen, and it also includes energy that is stored as bodyfat.

You will use carbohydrate energy as well as the stored energy from bodyfat whenever you are doing cardiovascular training, since your body can break down both forms of energy whenever you are in the aerobic training pathway.

If you exercise at a moderate intensity - approximately 70% of your maximum heart rate - you will burn through a higher percentage of bodyfat energy than carbohydrate energy. Likewise, if you exercise above the 70% threshold, you will still use both forms of energy, but a higher percentage will come from carbohydrate energy than from bodyfat. 

There is an age-old debate about which of those intensities is more effective, since most people are trying to lose bodyfat, and they could care less how much carbohydrate energy is being used. However, the (equally age-old) answer to that debate is that although you will burn through more carbohydrate energy at the higher intensity levels, you will also burn significantly more total calories by keeping your intensity above 70% of your max.

What about energy from Protein?

Here is where you have the chance to take charge of your own physiology and manipulate your body’s systems in order to maximize the amount of bodyfat that is burned during your cardiovascular training session.

Earlier, the concept of “the wall” was defined as the point whenever your body runs out of carbohydrate fuel. Also, remember that your body can burn through carbohydrates as well as bodyfat during cardiovascular training. One would think then, that by continuing to exercise after the carbohydrate energy had been depleted that the body would only burn bodyfat for energy.

That is true, up to a certain point, and here is where your level of intensity becomes absolutely critical to your success.

You see, the body can only break down stored bodyfat at a certain rate while you are exercising. Think of it as your body needing to travel a great distance to get bodyfat stores that have been in place for months, years, or even decades. That energy is in deep tissue storage, and your body will only be able to get to a certain amount of it during any given training session.

If your intensity level is so high that your body cannot break down energy fast enough from bodyfat storage, and you are also out of carbohydrate energy, then the only energy source left is protein that has been broken down into amino acids and stored in your muscles.

In laymen’s terms, what that means is that if you continue to exercise once you have run out of bodyfat and carbohydrate energy, your body will start to break down muscle tissue for energy!

To say that doing so would be a bad idea would by very much of an understatement!

• For one, your muscles power your metabolism, which in turn, powers your ability to lose weight. If you sabotage your metabolism by exercising intensely without enough available energy, you will actually GAIN weight in the long run.
• For two, you will very likely feel incredibly ill. I made this mistake one time (and one time only!) and I seriously thought I might be about to die. It took me days to actually start feeling normal again.  

Where’s the Middle Ground?

In order to beat your body at its own game, the trick is to not stop exercising when you run of carbohydrates, but rather to scale back on the intensity level.

For example, let’s say you are on a treadmill doing a fast walk at 4.5 mph and your heart rate is zooming right along at about 75% of your maximum. You will be screaming through calories, and getting a great cardiovascular workout at the same time. However something unexpected happens:

You start to get hungry!

In fact, you start to get SO hungry, that you are seriously considering stopping the treadmill, speeding back home, and scarfing down an entire box of Cheerios.

Don’t do it - stay right where you are!

That extreme level of hunger is your body’s natural ability to say, “Hey! I’m out of energy and I need a refill!”

Well, if you stop right there and give your body that refill, then what do you think will happen to that bodyfat storage that has been sitting on your hips or your stomach for the last 10 or more years? Yep - it’s going to stay on your hips or your stomach!

The opportunity now is to shred that bodyfat once and for all by simply scaling back the intensity of your workout to a level where your body can once again keep up with the energy demand by breaking down bodyfat to power the activity.

Coincidentally enough, for most people that will be right around 70% of their maximum heart rate, which matches up to the aforementioned “fat burning zone”.  

Also, one thing to note is that your extreme hunger will go away once you have scaled your energy consumption back to the point where your body can keep up with the demand again. I have been running outside and been more than 3 miles from my house when I hit the carbohydrate energy barrier and suddenly got extremely hungry. However, by simply slowing down my running speed to a lower intensity level, the hunger went away in less than 5 minutes.

Conclusion

Always remember that your body is a machine, just like any other machine that you are familiar with. There are certain processes that power certain activities, and there is a very specific “if this, then that” logic that underlies everything that happens in the human body.

By learning the basics of how your body utilizes energy, not only can you maximize the health and fitness benefits of your exercise program, but you can lose the maximum amount of bodyfat at the same time!