I live in the foothills and hike a 5 mile loop trail each morning 6 days a week. I hand carry (no sling) a M1 Garand which is pretty close to the weight of my hunting rifle. I also wear a backpack with a 20lb slab of iron inside. If the ground is dry or frozen, then at the end of the hike at the trail head I knock out 50 pushups, then shed the pack, and knock out 50 stomach crunches. If the ground is all sloppy wet, or the snow too deep, then I wait until back at the shack to do those. This routine also helps with my annual elk camp at 6000 ft elevation including a daily 1000 ft climb up to where the big racks live.
I average shooting practice once a week. From December to around April it's mostly fiddling with rifles, scopes, other equipment and all manner of ballistic gack. After that the focus shifts to weekly field practice of off-hand, off-sticks, tree limbs, fence posts, kneeling and sitting. I get all my prone practice from an annual trip to p-dog towns.
Oh, yea - I'm 68.