Upon stimulation by an action potential, skeletal muscles perform a coordinated contraction by shortening each sarcomere.

The myosin heads move in a coordinated style; they swivel toward the center of the sarcomere, detach and then reattach to the nearest active site of the actin filament.

[5] This process consumes large amounts of adenosine triphosphate (ATP), the energy source of the cell.

Muscle tissue also contains a stored supply of a fast-acting recharge chemical, creatine phosphate, which when necessary can assist with the rapid regeneration of ADP into ATP.

When the muscle no longer needs to contract, the calcium ions are pumped from the sarcomere and back into storage in the sarcoplasmic reticulum.

This type of muscle tissue is also capable of adapting to different levels of stretch and tension, which is important for maintaining proper blood flow and the movement of materials through the digestive system.

Acetylcholine, (a neurotransmitter used in skeletal muscle contraction) is released from the axon terminal of the nerve cell when an action potential reaches the microscopic junction called a synapse.

A group of chemical messengers across the synapse and stimulate the formation of electrical changes, which are produced in the muscle cell when the acetylcholine binds to receptors on its surface.

A coordinated and fine-tuned response to a specific circumstance will involve controlling the precise number of motor units used.

This allows for complex muscular coordination with little conscious effort, such as when one drives a car without thinking about the process.

At lower activity levels, when exercise continues for a long duration (several minutes or longer), energy is produced aerobically by combining oxygen with carbohydrates and fats stored in the body.

Aerobic ATP production is biochemically much slower and can only be used for long-duration, low-intensity exercise, but produces no fatiguing waste products that cannot be removed immediately from the sarcomere and the body, and it results in a much greater number of ATP molecules per fat or carbohydrate molecule.

Depending on the type, muscular dystrophy can affect the patient's heart and lungs, and/or their ability to move, walk, and perform daily activities.