Whether you are drawing from a model or from the imagination (as in animation), you should always be aware that you are not drawing bones, muscles, and cloth, or a model sheet drawing — you are drawing an action. Think of the figure as having gone from a “normal” relaxed pose to the gesture you are drawing. Attach, in your imagination, a rubber band at all joints at that normal position. Any part of the figure that moves will have to be moved under the strain of stretching the rubber band. Try to draw the effort it takes to stretch into the change of pose. Feel that if the figure relaxed it would snap back to normal. That is called “tension.” Being aware of whether it is an extensor (a muscle that pushes out or extends) or a flexor (one that pulls in or contracts) may help, as long as you keep in mind that it is not the muscle you are interested in but rather the idea or motivation behind it all. Look for the tension between foot and foot, elbow and elbow, or any part that pulls away from or pushes toward another part, or twists or any kind. Try this, but don’t think of it as an experiment, think of it as one of the main weapons in your arsenal of drawing helps.
Here are some examples from an earlier class. My correction drawings are necessarily simple, sometimes overly exaggerated and often crude. Anyway, most of you know by now that I think more highly of a crude sketch that tells a story than an immaculately rendered drawing that looks like a freeze-dried corpse. The first correction was an attempt to get the artist to loosen up. Holding the pen tightly right down near the nib plus trying to “draw” all the parts of the figure as parts of the figure has a stiffening and stifling effect on drawing. I suggested holding the pen farther up the shank and start drawing the action, i.e., the stretches, tilts, twists, and tensions. Feel the tension (the rubber band-stretch) between the upraised right shoulder and the outstretched right knee and foot, the tension between the two knees, and the twist caused by the arm having to stretch over to the left knee. You can even feel some tension in the neck as it strains to hold the head upright. Feel the whole figure pulling away from what would be a normal sitting pose.
The next pose was a difficult one. Ordinarily you would think of the shoulder as lifting higher if it is leaned on. In this case the other arm was stretched straight as she pushed on her leg, forcing that shoulder higher. It meant having to show some of her upper back to suggest that it went up beyond the neck (here is a front view of what is going on) where it could logically meet the pushed up shoulder of the straightened arm. If you are looking for lines on the model to divulge something to copy, they may not always be there. You have to look for the “story” in the tensions, twist, stretches, and squashes that will reveal that story.
Here is one where I perhaps went a little overboard, but you can spot the crux of the problem quickly. You can feel the “elastic bands” pull from all points to all other points. This kind of tenseness is not rigidity or stiffness, it is the stretchable, flexible, resilient, supple kind. It allows your figures full play (and beyond) in performing their body language. There is a study in contrasts here also, where the knees are forced dramatically apart while the hands are pressed together with the pelvic area establishing a solid base for the rest of the body, which has suddenly taken an interest in something off stage right.
Just as some drawings are only an illusive nuance away from being breathtakingly expressive, so are some drawing techniques one untried idea away from becoming successful, forceful, and dynamic. So strive for a drawing technique that is flexible in helping you to communicate the story you are trying to tell. Communication is what makes an artist a great artist.