The ATP required for continuous muscle contraction during endurance activities comes from anaerobic respiration and oxidative phosphorylation.
The process of breakdown of substrate glucose in the absence of oxygen is called anaerobic respiration. This process primarily takes in some unicellular organisms.
In humans, during endurance activities, a continuous supply of ATP is required. The ATP reserves in muscles are very small. Thus, there is a requirement for metabolic pathways to maintain continuous ATP supply and resynthesis.
These pathways are phosphocreatine breakdown and muscle glycogen breakdown which enable anaerobic substrate level phosphorylation and aerobic phosphorylation.
Therefore, the ATP required for continuous muscle contraction during endurance activities comes from anaerobic respiration and oxidative phosphorylation.
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