I mean, I know this sounds silly, but the adage "Train like you hunt and hunt like you train" is quite applicable here. I also live in the mountains and I found a regular regime of hiking with ever increasing weight to my backpack was crucial to proper fitness and endurance.
All of the fancy training programs and books bely the fact that actually going out and doing what you need to do to get ready is the best medicine for success. For me, I just hike about 2-3 times per week with varying levels of elevation gain and increase the amount of feet climbed and weight carried until about a week before the hunt, then rest. Boom, instant readiness.
I don't know your experience with hunting, but on a day of success in the backcountry for whatever animal, I am usually looking at a 10-18 hour day of hiking and hauling, with my Garmin telling me 20-25 miles over unloved terrain.
Oh.. one last thing, Ibuprofen is your friend when you get sore.