Voluntary!

Education is what remains after one has forgotten everything he learned in school - Einstein

Skeletal muscle

Attached to the skeleton or connective tissue via tendons. It is under "voluntary control" but can tire quickly. Between the origin and insertion of a muscle is the muscle belly; muscles can have multiple origins, insertions and bellies.

Skeletal muscle is able to contract, respond to stimulation from the nervous system and hormones, stretch beyond its normal resting length i.e. bad bike fit and recoil back to its original resting length.

This is done under the great effort of conscious control of the brain.

You can't fake it! You earn it!