As I read the various posts, I can't help but notice we're not the youngest group, and because of that some of us need to recognize our limitations, and avoid possible injury. You can't hunt Elk or anything else if you can't walk.
I'm not saying you can't be fit, but some regimens may not be suitable due to our age and the obstacles that come with age, such as arthritis.
I'm 48 and have spent the last 27 years of those 48 years on active duty in the Army. So, you could say fitness has been a regular part of my life, and as a 48 year old I'm facing some difficulties in maintaining a high fitness level. So here goes my two cents, take it for what it is worth, and remember you get what you pay for.
This challenge really started back in 2008 when I was diagnosed with stage 4 Hodgkin's Lymphoma. After undergoing 8 months of chemotherapy I knew that the idea of doing 500 lb squats and deadlifts, and 250 lb military presses were a thing of the past. The arthritis that I held dealt with previously now was a daily obstacle, and my body was a mess, also known as a bowl of jello, from the chemo.
So what did I do? I have slowly worked my way back, but still have a long way to go.
With the limitations presented by the arthritis, and other lingering effects of chemo. I walk and do hike with a pack, but limit weight and never run with a pack. (For those who do, more power to you, but the impact your knees are enduring is immense, be careful.)
Weightlifting is a regular part of my regimen. Usually a simple circuit of standing presses followed immediately by pull-ups for a set with short rests until completing five sets. Builds the muscles involved in shooting. Additional word on weightlifting, get off the bench, lifting on your feet has the additional benefit of building your core, and makes your body more functional. Of course this may mean lighter weights, and a dedication to form. Sounds like good practice for shooting, doesn't it?
Also, I regularly hit the kettlebells, simple swings will challenge you aerobically (cardio) without the impact of running or even carrying a weighted pack. Additionally, the sledgehammer gets regular use on an old stump in the back yard. Great workout and a great stress reliever. You can use a tire instead of a stump, but the stump didn't cost me a thing.
Sorry about the long post, but I've seen some ideas from others that I can use, and I was hoping someone could draw an idea or two from my experience.