Weight training is an important part of my hiking/backpacking preparation. When I hike, I find that there’s not much of a cardio involved, instead more leg and abdominal strength is needed. In the areas that I hike in the northeast, mainly along the Long Trail, I tend to hike a consistent two miles/hour. Instead of a cardiovascular running type activity, my hiking tends to be an up-hill, down-hill walk over roots and branches.
Thus, I tend to jog for a mile or two as a warm-up. For the main part of my workout, I lift weights, with a focus on my legs and abs. I’ll start by doing leg presses on the sleigh, usually 4 sets of between 600 and 850 lbs. Then, I’ll do calf raises and calf raises, 4 sets between 350 and 450 lbs. Next, I’ll switch between leg extensions and curls. Finally, I’ll left my toes, while keeping the balls of my feet on the ground until failure.
My ab workout is pretty extensive. I have a friend who does gymnastics, so I just try to keep up with her (but always seem to fall short). We do a lot with our sides, as well as the usual upper, middle, and lower abs. Having a strong core seems important for hiking/backpacking.
Again, where I live/hike that type of training seems more important to me. I never really get up to a speed where cardio training comes into play. This might be different for people living in regions with flatter, less root-bound trains.