Some of the workouts guys post here are knee intensive. I'm not one to tell another what kind of workout they should be doing, but If I was younger and had what hopefully would be years of hunts ahead of me, I would be looking at workouts that didn't maximally stress the knees or shoulder joints.
Ditto on the above. I'm not into "workouts" counting carbs, protein, etc etc. and if I had to spend time in a gym to be fit to hunt I'd put a bullet in my head and quit hunting...in that order.
Having said that, different strokes for different folks applies. The only advice I feel qualified to give is in the quote above.
You pound those joints you WILL LIKELY pay for it sometime after age 50, I don't care what kind of "shape" you're in.
Take care of your joints, you have no spares.