For more of a challenge yet, see Vasisthasana Pose, Yoga one Stage IV, on 265 in Chapter 14 Scoliosis. That version leads into the full pose Yoga one from Downward Dog. This pose strengthens the back of the shoulders and stretches the front of the shoulders.
This pose promotes freedom of movement between the arms and chest, stretching the front, strengthening the back, and coordinating the two. In 1997, there were 117,000 hip replacements associated with hospitalizations for arthritis. 1 Aging runners, soccer players, dancers, athletes of all kinds, and many who do not have a particularly active past find themselves unable to tie their own shoes, or find that walking, possibly just standing, or even riding in the comfortable seat of a luxury car for any length of time is painful.
If they had an injury in the upper extremities they would have more leeway: they could turn the key with the other hand, move closer or farther from the easel, carry a package differently. But walking requires the uniform use of all parts of the legs, and every joint in one leg bears all the weight with each step.