Muscles transfer force to bones through tendons. One muscle of the pair contracts to move the body part, the other muscle in the pair then contracts to return the body part back to the original position. ... Muscles that work like this are called antagonistic pairs.

How are muscles antagonistic?

In an antagonistic muscle pair as one muscle contracts the other muscle relaxes or lengthens. The muscle that is contracting is called the agonist and the muscle that is relaxing or lengthening is called the antagonist.

Why do muscles work in opposing pairs?

Skeletal muscles only pull in one direction. For this reason they always come in pairs. When one muscle in a pair contracts, to bend a joint for example, its counterpart then contracts and pulls in the opposite direction to straighten the joint out again.