Introduction to Exercise Physiology
I will understand if biology aficionados cringe at my over-simplification of ATP production and energy cycles. Bear with me =)
When you exercise, your muscles require oxygen to function. In response, you breathe faster and your heart rate increases in order to take in more oxygen and deliver more (O2 rich) blood to your muscles. At the same time, your muscles need ATP (adenosine triphosphate), the body′s main energy resource, to contract.
A small amount of reserve ATP is stored in the body for temporary use; however the majority is produced from the breakdown of nutrients in your diet. Through digestion, the nutrients are broken down and passed into the blood as lipids (fats) and glucose (carbohydrates).These nutrient monomers are passed from blood capillaries into muscles, where (at a microscopic level) they are used to make ATP.
Fats, Carbohydrates and Protein: Fuel for ATP and Exercise
When the body is resting, the primary energy source for ATP production comes from fats (~70%) while the rest is from carbohydrates (~30%). As the intensity of an activity increases, the fuel source for ATP shifts to use more carbohydrates. Given the limited storage of glycogen in your liver and muscle however, fats will once again become the predominant energy source as the duration of the activity lengthens.
Evidently, there is a constant shift between the usage of fats and carbohydrates for ATP that varies with the intensity and duration of exercise and the organic materials available in your body. This fact is particularly important for your fitness performance:
While the accessibility of fats in your body is not a concern, the restricted amount of carbohydrates that can be stored (enough to fuel ~90 minutes of continuous exercise) may pose a problem. As the first fuel source to be depleted, carbohydrates are consumed even faster during high intensity activities. Once this carbohydrate reserve is used, the body will break down protein for energy. It is best to avoid this since protein is used to build muscle tissue and other metabolic processes.
More details on NUTRITION to accompany your training regime can be found here.
Energy Metabolism
This refers to the production of ATP. ATP is generated within the muscle fibers through chemical reactions that transform energy from food into energy that the body can use. The rate and amount of ATP production is dependent on the specific demands of an exercise. For example, slow and low intensity activities (walking, leisure swim) are reflected by a slow rate of ATP generation and vice-versa for faster, intense exercises (running, soccer). Essentially, the yield and rate of ATP assembly dictates the chemical pathway that ATP is produced: aerobically (in the presence of oxygen) or anaerobically (without oxygen).
Each energy system is distinctive in their rate of ATP production and their contribution to the body′s total ATP. Accordingly, the body depends on all three systems simultaneously and will draw from each depending on how much and how quickly ATP is needed.
Click here for a more thorough discussion and examination on ENERGY SYSTEMS.
Related Pages:
Exercise: Energy Systems - Learn how your body uses it's energy stores in different types of exercise.
Beachbody P90X Home Workout Review - A full overview and critique of Tony Horton's famous P90X workout program.
Body Mass Index - Learn whit BMI is and how it can be used to gauge your health level.
