fit as a fiddle

(as) fit as a fiddle (in good health) — в добром здоровье, здравии; в отличной форме (о человеке), бодрый, здоровый; (чувствующий себя) как нельзя лучше; совершенно поправиться, совсем здоров; в прекрасном настроении

Example: There's nothing wrong with her father, she tells him. Her dad is as fit as a fiddle. It's simply that he's getting older, she says matter-of-factly. After all, all of them are. Her own memory isn't what it was, and neither is his. She reminds him, not so gently, that he forgot his own daughter's birthday, forgot his son-in-law's name. (Joann Kobin, "Dr. Leopold Needs a Little Help", 2007)

See also
[fighting fit]
[alive and well]
[vim and vigor]
alive and kicking
[clean bill of health]
[как огурчик]