Originally Posted by
Bill Anders
Matthew,
Thru-hiker (PCT 2015) and seasonal backcountry trail crew volunteer here. I feel your struggle, especially as I push closer to my mid-50's. You'll find over the years that the lifting prescribed here will make those trips easier, but it cannot and will not replace a few good prep hikes, as Rip mentioned above.
I have made that mistake going into the first backcountry trip of the year, thinking that the lifting would suffice. It never does, especially with a loaded pack (crew trips are 20-40lbs heavier than hikes for fun). So if you can get an overnighter between now and the end of August, with comparable distances on the days either side, you should feel significantly better.
Outside of your lifting, the real off-season workout for that neck of the woods is backcountry skiing or snowboarding <<edit - especially snowshoeing>>. It keeps those muscles used to that sort of workout.
Good luck!
Bill