The best way to get in shape for backpacking is to stay fit with regular exercise. When starting backpacking as a form of outdoor recreation, specific areas of the body must be strong and in shape. Strengthening leg muscles is only one part of getting in shape for backpacking. It's also important to have a strong core, or back and abdomen muscles. Keeping ankles, knees and hips flexible also is imperative when you face inclines or steep hills. You must build endurance over time and increase it as you approach the date of an excursion that will last longer than your average backpacking trip.