Sinewy (adjective)

Having strong, tough, and flexible muscles or muscle fibers.

Origin:

From sinew.

Examples:

1. He had a sinewy strength that belied his age.
2. The sinewy strength is a result of his training.
3. The sinewy man easily lifted the heavy box.
4. The sinewy arms of the statue were impressive.
5. The sinewy muscles are visible through the skin.