When you are learning how to draw the human figure, it helps bring your drawing to life when you use gesture correctly. People's gestures are very dynamic and showing their gestures are key when draw the human figure.
Imagine for a moment that the body is 3 blocks; One block for the skull; One block for the rib cage and one block for the hips. These blocks can be positioned any way you want and then once the gesture is established, the arms and legs have very few options left for them to be placed in … In other words, once you find your gesture, your drawing is almost done .
In a drawing with good gesture, you should be able to draw a line down the center of your figure.
That line should twist with the angle of the shoulders, hips and skull, so that the line has an "S" shaped curve to it. Once the 3 blocks are positioned so that the "S" is established, the next step is to be concerned with the direction the 3 blocks are facing. The 3 blocks should not be facing the same direction. Try drawing 3 blocks all facing the same direction and see how flat the drawing looks.
Now draw the head and hips facing the same way and the rib cage facing a different direction. Notice how dynamic and round the gesture once once you have drawn it with those angles.
A really good example of this principle is Michelangelo's "David". There are no two points on this figure that are parallel, for example, shoulders, hips, hands, feet, etc. The head, chest and hips are facing slightly different directions in this sculpture.
Creating a good "S" curve is the first step in any drawing or sculpture. All of your anatomy will be subservient to the gesture. For example, if your gesture indicates one hip lower than another, then one leg is going to be straight and one has to be bent.
The bottom line with gesture is, if you start drawing with the "S" shaped curve, you have a good base to start a figure from.