Muscle Recovery and Fatigue

Any intense physical activity escalates the ATP demand in the muscles.

As contractions become vigorous, the compressed blood vessels impair the tissue's oxygen supply.

Under low oxygen conditions, muscles turn to anaerobic glycolysis for ATP production, ultimately generating lactic acid.

The lactate and the hydrogen ions released from ATP hydrolysis reactions accumulate in the cells.

As a result, the tissue pH declines to cause lactic acidosis, preventing the muscles from contracting anymore.

These fatigued muscles need time and surplus oxygen to generate ATP for recovery.

Once oxygen levels are elevated, the enzyme lactate dehydrogenase converts accumulated lactate back to pyruvate.

The pyruvate is either used by mitochondria to produce more ATP or enzymatically converted to glycogen for storage.

The surplus ATP is used by the enzyme creatine kinase to build the phosphocreatine reserves.

Additionally, the muscles shunt some of the excess lactate to the liver to be converted back to glucose via the Cori cycle.

This glucose is then returned to the muscle tissue to build glycogen stores or produce ATP.