fighting fit

(be /get) fighting fit (in good health) — в отличной / прекрасной форме (о человеке); ~ здоров как бык

keep fighting fit — поддерживать себя в отличной форме

Example: Here's your chance to get fighting fit. Join our 3 week fitness programme.

Example 2: What kind of sport would you recommend to keep fighting fit?

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