The muscle on the left lost it, as I suspected he might.
As small muscles lose their nerve supply they can create a cramping feeling.
The muscles around his eyes lost a little of their tension.
In general, muscles, blood vessels and other tissues lose their elasticity.
The technique doesn't leave one, but, like skiing, the muscles lose their sharpness.
His muscles lost all strength, and he toppled limply onto the floor.
But when the mattress is holding you up, your skeletal muscles lose tone.
By the time they'd learned, their muscles had lost all tone.
The bronze man's sight blurred; his huge muscles lost the feeling of movement.