Your glute medius and minimus are heavily used in walking and hiking or biking. These muscles stabilize the hips in relation to the legs and strengthening them can help with back pain by assisting your core. To work them out properly there are a number of strength training moves you can do which are particularly good with a band for added tension. Try a lateral shuffle or a banded leg lift. There is also an exercise called the Banded Monster Walk, which uses a band to maintain tension in the legs while walking in wide stance.