This. My wife and I spent the summer in WY & CO camping in our trailer and hiking nearly every day. Most days we hiked between 4 and 10 miles. I carried my hunting pack with the same stuff I carry on a day hunt and carried my bino pack/pistol. In a little less than 3 months I lost 25 lbs and came home ready for hunting season in the best shape of my life.If you want to hike uphill efficiently with a pack on, then You are going to need to hike uphill with a pack on. Conditioning is a very specific adaptation, so if you were only going to do one thing, put on a pack and go rucking.