By Matt Watt
Today I’d like to give you a little information on how your body gets energy when you are exercising. As a trainer, I think people benefit from knowing the basics of exercise physiology.
If you are one of our boot campers, you know that the DeVetter Fitness boot camps consist of cardiovascular, strength, agility, balance, power and flexibility exercises and workouts, all of which require different types of energy from the body at different times, depending on what activity you are doing.
Energy is what makes the body go, to put it simply. However, what kind of energy you are using depends on the intensity and duration of the workout you are doing. So let’s jump right into it and explore where your energy comes from.
For the body’s cells to use energy, they must break down the foods we eat in a way that conserves most of the energy contained in carbohydrates, fats and proteins.
The radiant energy from the sun is captured by plants and used to turn simple atoms and molecules into carbohydrate, fat and protein.
In addition to conserving energy from carbs, fat and protein, the final product of the breakdown must be a molecule the cell can use. This molecule is ATP, or adenosine triphosphate. Cells in the body use ATP as the primary energy source for you to do work. Think of it as the body’s energy currency.
Let’s start with the immediate sources of energy.
Creatine phosphate, or CP, is another energy phosphate molecule that is stored in the muscle and is the most important immediate source of energy. CP can donate its phosphate molecule to ADP (adenosine diphosphate) to make our energy currency, ATP. Unfortunately, the CP store in muscle only lasts about 3 to 5 seconds when the muscle is working at a maximal effort. This process does not require oxygen which means that it is an anaerobic energy mechanism to produce ATP. This is used during activities like jumping, or the first seconds of a sprint.
Next is the short term source we use to get energy.
As the muscle’s store of creatine phosphate decreases, the muscle fibers break down glucose, which is a simple sugar, to make ATP at a high rate. The glucose is obtained from blood or the muscle’s glycogen store. Glucose metabolism is called glycolysis and it does not require oxygen to function, just like the breakdown of creatine phosphate. To sum things up, glycolysis produces 2 ATP for our body to use as energy.
However, glycolysis only lasts for a limited time. When you are working at a high rate, the product of glycolysis is no longer 2 ATP, but rather, lactic acid. The accumulation of lactic acid slows glycogen metabolism and can interfere with the mechanism involved in muscle contraction. We have all felt this before. It’s otherwise known as “the burn!” This short-term source of energy is used in activities lasting about 2 min. One example would be a 400 meter dash.
Last but not least, we have our long term sources of energy and this is usually the first to be used.
This process produces ATP from a variety of fuels and requires oxygen, meaning that it is aerobic. The main fuels include, muscle glycogen, blood glucose, plasma free fatty acids, and intramuscular fats. Glucose and fats are broken down in glycolysis and to put it simply, we make ATP with the energy extracted from the glucose and fat.
This process requires oxygen which is what makes it “aerobic.” ATP production via aerobic mechanisms is slower than production from the immediate sources I talked about earlier. One reason for this delay is the time it takes for the heart to increase the delivery of oxygen enriched blood to the muscles at the rate needed to meet the ATP demands of the muscle. This type of energy source is used for longer durations like jogging.
So hopefully you learned a little bit more about your body and why you feel the way you do during certain exercises and workouts. Not too complicated right? There is a lot more to know and like I said before, as a trainer I feel that it is good to know the basics about what happens in your body during exercise. I hope this was beneficial to you and thanks for reading!
Howley, Edward T, and B Don Franks. Fitness Professional’s Handbook. Champaign IL: Human Kinetics, 2007. Print.
