Utkatasana is a good example of the principle of simultaneous expansion in opposing directions (see figure 5, page 34). The ideal here would be to squat down until the thighs are parallel to the floor; then the trunk and arms lean forward as the body regains its center of gravity. This extreme gives the optimal effect in regard to strengthening the leg and buttock muscles. The other extreme is to keep the back completely upright, without bending the legs enough. In this case we would compromise the powerful work of the legs and buttocks, which occurs only in a deep squat. The ideal is a balance between these two actions, working simultaneously in both directions.