Look for the line of balance or the centre of gravity in a standing figure: it begins at the top of the skull and passes through the middle of the nose, straight down the middle of the chest cavity. With a back view, the line starts from the back of the neck on the spinal column. From a side view this line of balance starts at the back of the ear and travels down to the weight-bearing foot.
The line indicating the central axis also helps indicate where the body mass or majority of the body weight is placed. If the figure moves or if the model sits down, the weight or mass changes to a different area of the body.
Move around the model before you begin to draw to get a sense of where the figure is in its allotted space and to identify its centre of gravity and gesture. Mark the central axis in your initial sketches of the standing figure. Ask the model to change poses every two to five minutes. Draw as many quick poses as you can.
Following are the accumulation of drawings done in the life drawing class over three weeks. Red lines show centre of gravity were superimposed with computer software. I found this exercise difficult as I have not control of posture of the models nor the view. Both models are difficult to draw as they both are quite muscular but not as defined as those Greek sculptures. I can see the muscles but somehow they look in wrong shapes. The problem is particularly profound when the body part is foreshortened.