What is the chemistry of muscle contraction?

Chemistry of Muscle Contraction
Muscle contraction requires a plentiful supply of ATP. ATP can be made available in three ways:
Muscle cells are generously supplied with mitochon­dria, within which ATP is formed by means of aerobic cellular respiration.
Muscle cells contain creatine phosphate, which is used as a storage supply of high-energy phosphate. Creatine phosphate does not participate directly in muscle contraction. Instead, it is used to regenerate ATP by the following reaction:
creatine~P+ ADP ~ ATP + creatine
When the creatine phosphate supply has been depleted, a muscle cell can still produce ATP anaerobically. Anaerobic respiration occurs when the cells are not being supplied with oxygen quickly enough to make aerobic respiration possible. This would occur, for example, during times of strenuous exercise. In practice, anaerobic respiration can supply ATP for only a short time because a waste product called lactic acid builds up, resulting in muscular aching and fatigue.
Oxygen Debt 
We have all experienced the fact that, following strenuous exercise, we continue to breathe deeply and pant, even while resting. This continued intake of oxygen is required to complete the metabolism of lactic acid that has accumu­lated during exercise and represents an oxygen debt that the body must pay to rid itself of lactic acid. The lactic acid is transported to tlle liver, where it is completely broken down to carbon dioxide and water.
ATP is required for muscle contraction and can be generated by way of aerobic or anaerobic cellular respiration and from creatine phosphate. During anaerobic cellular respiration, a waste product called lactic acid is produced. Lactic acid represents an oxygen debt. since oxygen is required to metabolize this product.