My grip on him relaxed; the muscles felt like water.
It was so long since she had done that, her facial muscles felt strange.
His muscles felt as if they had frozen in place.
Part of this is enjoying how good your muscles feel while doing light work such as walking.
The muscles felt as if they'd been sculpted of stone.
The muscles felt a little stiff, but that was all.
All at once, the muscles around her heart felt tight.
Why, for example, do muscles feel sore a day or two after they are stressed?
Consider: what chemical do you know makes your muscles feel tired?
A bit of this, and one's muscles feel like butter.