Practice yoga once a week. Carrying a backpack compresses your spine, and yoga postures such as downward dog and the sun salutation stretch it out again. (Both can be done anywhere and are beneficial morning rituals before a day of trekking.) To learn more about these and other yoga poses, check out www.yogajournal.com.
Use your training hikes to fine-tune pack fit and break in your boots, so you don’t spend the first day of your trip futzing with straps and moleskin to eliminate sore spots.
At the gym–or just using gallons of water at home–do sets of shoulder raises, both to the front and sides. Building shoulder and upper-back strength helps ease the burden of lifting your pack and makes it easier to maintain a comfortable posture all day on the trail.