Understanding how your body generates needed energy for exercise can improve your performance. Like most body systems, energy production is not a simple process, but knowing the basics can bring your athletic abilities new life; you will be able to give your body what it needs in order to meet the demands you place on it.
Anaerobic Exercise Energy Review
Muscles contract both in the presence of oxygen (aerobic) and in the absence of oxygen (anaerobic). At the beginning of exercise and during intense training, immediate energy is produced by anaerobic energy systems that break high-energy bonds to provide fast energy, adenosine triphosphate (ATP), to working muscles. Not only is this form of fast energy production relatively inefficient, but one of its by-products, lactic acid, can interfere with muscle contraction and impede your athletic performance. The accumulation of lactic acid, also called lactate, in the muscle causes an uncomfortable burning feeling that sometimes causes you to stop exercising. How long you can sustain high-intensity exercise depends heavily on the availability of stored fuel (glycogen) in the blood, muscles, and liver. Carbohydrate loading, a sports nutrition strategy used by athletes before an endurance event, can increase the stores of muscle fuel to be used during exercise. (See The pre-event meal: What to eat before you approach the starting line.)
Aerobic Exercise Uses Different Sources For Energy
Although anaerobic energy production provides immediate energy, only a limited amount of energy can be generated in this fashion. Aerobic energy production, which takes over when all preliminary sources of energy production have been exhausted, occurs in the mitochondria of the cell and has the capability of long-term energy (ATP) production. This is the fuel-production method that carries you through a 5K run, a walk-a-thon, a cycling century, or swimming laps in the pool. The mitochondria are small organelles that are known as the “power houses” of the cell. As the number of mitochondria increases, so does the potential for converting fuel into ATP. By exercising regularly and by continually challenging yourself, you increase the number of mitochondria in the muscle, and therefore, the ability to make more energy during exercise.
Carbohydrates, Fats, and Energy Production
The body breaks down carbohydrates and fats to produce ATP during exercise. The body favors carbohydrates to fats, and although it can be used for fuel when necessary, protein is not a preferred fuel. Metabolic processes known as the Krebs cycle and the electron transport chain need oxygen to release the energy that is stored in the bonds of these macronutrients. Appropriately, this process is named aerobic metabolism, and it fuels the body for aerobic activities, such as walking, jogging, cycling, swimming, etc. Compared to anaerobic energy metabolism, but aerobic energy metabolism is slower. To be able to carry out continuous high-intensity or endurance exercise, muscles must have an uninterrupted supply of energy. A common strategy of sports nutrition is to supply ample calories during exercise to be able to exercise longer. (See Sports nutrition: Eating during exercise.)
Protein Consumption During & After Exercise Spares Stored Energy, Muscle, & Boosts Immune System
Ivy and Portman provide much evidence for the benefit of the addition of protein to carbohydrate during and after exercise. In their book Nutrient Timing, the two men support that by consuming carbohydrate plus protein during and after exercise, muscle tissue breakdown is decreased and is spared to a greater degree than by ingesting carbohydrate alone. To repair muscle tissue broken down as a result of the physical forces associated with weight-bearing exercise, the body prefers to use ingested protein over muscle protein. Muscle tissue protein is also broken by cortisol, a hormone that is produced in increasing amounts as the intensity of exercise grows. The detrimental effects of cortisol continue into recovery continuing to breakdown muscle and suppressing the immune system.
This description of energy production during exercise, emphasizes carbohydrate intake before exercise and carbohydrate plus protein intake during and after exercise for improved exercise performance.