Fishingkid, Fair question.
When i was younger, one of my friends was about 10 years older than me and he went to Wyoming hunting for a month every year. The guy ran laps and stairs at the high school every evening starting a couple months before our local seasons. I did that too...but just not at the consistent level that he did.
I was fortunate to have a large Ranch to hunt that was owned by my Grandfather. My thing was scouting on foot from the Ranch House before season. I scouted every night and i really used to push myself when hoofing it up hills and ridges. As hard as i'd go, i'd tell myself that i needed the work and push even harder.
Between the running and the scouting, i stayed in as good a shape as anybody. Did so for many years.
"It's all about knowing what your firearms practical limitations are and combining that with your own personal limitations!"