The danger is wearing out or overusing certain muscles and nerves.

Examples of this include certain muscles in the hand.

This is the ridge where certain muscles are attached to the bone.

It was hard to see the change of expression on the commander's face, but certain small muscles set firmly.

Spent or not, she kept certain muscles contracted to hold him inside her.

I don't have the problem of knowing where certain muscles belong.

Such symptoms tend to occur when attempting to move certain muscles after rest.

There are certain muscles in the mouth, he told me, that must be developed "early."

After the seizure, the patient usually has temporary weakness in certain muscles.

Activities that promote endurance or strength also tighten certain muscles at the expense of others.