Balance and Movement

These images come from Andrew Loomis's Figure Drawing for All It's Worth - this is a highly recommended book, the material inside is pure gold!

Notice what happens to the torso of the figures in the top row when the balance in the legs shifts. When one leg receives the majority of the body weight, its hip and the opposing shoulder move up.

In the above image look at where the legs are positioned. The leg that has the majority of body weight will move under the mass of the torso. The leg that has less weight will either be posed in motion or it will move to keep the body from falling over. The second figure from the left in the bottom row illustrates this point. The figure's left leg is under the mass of the torso to support it, the right has moved out to keep the body upright. Think of this pose as similar to a bike and its kickstand. The main weight of the bike will sit on the wheels while the kickstand is angled out from the mass of the bicycle to prevent it from falling over.

Keep in mind that if you are going to draw an unbalanced figure (that is a pose that a model cannot hold for more than a fraction of a second) then it must have momentum, otherwise your figure will be locked in a static pose that looks as if is tipping over.  Loomis's advice is to angle the figure in the direction of movement.  The third figure from the left in the second row shows this purposeful balance/momentum combination.