I don't do owt specifically to be gig-fit...
However, in order not to be completely broken when I reach my late 60s (not too long now!) - also having two herniated discs - I do a morning routine of exercises involving crunchies, press-ups, Pilates stuff, Yoga stuff, Mars Bars and a Flake plus squats, some weights etc. And about 5 times a week I walk up our local hill, which is about 1000' climb.
And when I can be bothered I go out on the mountain bike, and go climbing and/or mountain walking.
Bass wise, I do various hand and wrists stretches as part of my routine, as well as doing an hour or so practice every couple of days.