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The aerobic energy pathway is the third and slowest ATP producing pathway that is oxygen dependent. This energy pathway typically supplies the bulk of the body's energy during exercise—after three minutes from the onset of exercise until the end, or when the individual experiences fatigue.
The process that converts the chemical energy of food into ATP (which can release energy) is not dependent on oxygen availability. During exercise, the supply and demand of oxygen available to muscle cells is affected by duration and intensity and by the individual's cardio respiratory fitness level. [1]
For multicellular organisms, during short bursts of strenuous activity, muscle cells use fermentation to supplement the ATP production from the slower aerobic respiration, so fermentation may be used by a cell even before the oxygen levels are depleted, as is the case in sports that do not require athletes to pace themselves, such as sprinting.
The production of ATP is achieved through the oxidation of glucose molecules. In oxidation, the electrons are stripped from a glucose molecule to reduce NAD+ and FAD. NAD+ and FAD possess a high energy potential to drive the production of ATP in the electron transport chain. ATP production occurs in the mitochondria of the cell.
The energy used by human cells in an adult requires the hydrolysis of 100 to 150 mol/L of ATP daily, which means a human will typically use their body weight worth of ATP over the course of the day. [30] Each equivalent of ATP is recycled 1000–1500 times during a single day (150 / 0.1 = 1500), [29] at approximately 9×10 20 molecules/s. [29]
The available oxygen and energy supply, and disturbances of muscle ion homeostasis are the main factors determining exercise performance, at least during brief very intense exercise. Each muscle contraction involves an action potential that activates voltage sensors, and so releases Ca 2+ ions from the muscle fibre 's sarcoplasmic reticulum .
In aerobic respiration, oxygen serves as the recipient of electrons from the electron transport chain. Aerobic respiration is thus very efficient because oxygen is a strong oxidant. Aerobic respiration proceeds in a series of steps, which also increases efficiency - since glucose is broken down gradually and ATP is produced as needed, less ...
The combination of an inappropriate rapid heart rate response to exercise with heavy or rapid breathing is known as an exaggerated cardiorespiratory response to exercise. [3] Due to the confusion between muscle fatigue and muscle weakness, there have been instances of abnormal muscle fatigue being described as exercise-induced muscle weakness.