Energy Metabolism and Supply for Exercise
When participating in exercise, and choosing which type of exercise training is best for your goals, it is important to have an understanding of the metabolism (breaking down) of fuels (carbohydrates, fats and proteins) to produce energy in the form which skeletal muscle uses for exercise.
Adenosine tri-phosphate (ATP) is required to power all forms of biological work, provide cells with a means of storing and conserving energy. Immediate energy is supplied by ATP and creatine phosphate stored in muscles. Anaerobic energy required for fast movements or resistance to movements at a given speed. This is useful for athletes that participate in exercises that involve a lot of fast twitch fiber contractions (the most powerful yet the fastest fatiguing fibers) such as sprinting or powerlifting. But also used in many other sports in combination with other fibers such as football which requires sharp sprinting movements but also a lot of aerobic ability.
The Role of ATP and Glycolysis in Exercise and Fitness
Anaerobic ATP production works without oxygen, supplying energy fast but inefficiently with the majority of energy lost in the reaction as heat. The biochemical breakdown of ATP, anaerobically, is shown below:
ADP + P +H⁺ ↔ ATP + H2O
Pcr + ADP + H⁺ ↔ATP + Cr
Pcr (creatine phosphate), ADP (Adenosine Di-Phosphate), P (Phosphate), H⁺ (hydrogen ion), ATP (Adenosine tri-phosphate, Cr (creatine).
This process, known as Glycolysis, is required for immediate high intensity exercise. ATP is broken down to ADP, giving energy for the contraction, but also releasing lactate (a suggested cause of fatigue). The process is reversible with the phosphate group rejoining ADP to once again become ATP.
Aerobic ATP production (required for longer term endurance exercise) involves the electron transport chain, oxidative phosphorylation, β -oxidation and the krebs-cycle, These processes work individually of each other yet combine to produce ATP to meet the demands of the exercise. These systems involving the aerobic break down of glycogen and the breakdown of the bodies largest store of energy, fats, into a useable form.
Muscle contraction is achieved though Myosin ATPase, this splits ATP with the energy from this being used for muscle contraction (the rate of splitting is increased when actin and myosin are joined). Cross-bridge cycling continues as long as Ca2⁺ concentration remains at a sufficient level to inhibit troponin-tropomyosin system. Actin and myosin remain separate as long as ATP is present (rigor mortis is a prime example of this as the reaction is stopped, causing the temporary stiffness of the body).
Energy utilisation is dependant on type and intensity of exercise. Short term – High intensity exercise (dependence on anaerobic systems). Long term – endurance exercise ( dependence on aerobic systems). Fatigue is an inability to maintain a given level of physical performance, caused through an inability for the muscles to meet the demands of the exercises.