This is something I personally do a lot of, whenever I see something interesting or slightly out of ordinary regarding peoples movements. One aspect of movement that is great to study is the way people use hand gestures when talking, a huge part of personality and conveying speech in animation. more so than the mouth itself. Each person does it more or less, depending on the subject and how they visualise their hands, its great.
The difficulty with observing movement is the documentation of such movement. Applying some of the animation techniques to the walk can help us breakdown what we see into their respective key poses, Contact, Down, Passing and Up. This is great as depending on the type of walk the arms in relation to the legs may be different. i.e. Arms widest on the down pose is fairly normal while arms widest on the up is similar to that of a skip. Arms widest on the contact often shows determination, powering the walk through the arms rather than having them trail through passively. Using this we can draw a single pose that represents where the arms are at what times and which aspect of the movement has the most emphasis.
For these though, I've trailed my hand following the movement of the various aspects of the body as it moved. while in others I have drawn key poses and trailed a line throughout. Some of the movement is especially interesting as we rarely move linearly to our destination and oftentimes arc through our movements.
Some of these are done with both hands, following 2 parts of the body simultaneously. Though very difficult it helps create a relationship between 2 points of movement as the joints often entail the furthest reaching part to go much faster and wider than that of the joint itself. Lines of course, good for following the movement but difficult to read back into at a later date. Some movements can be easier to follow than others depending on how complex the movement is and how much perspective is involved.
Some I added a figure, as a reference to which arm trails through what points. otherwise the lines could represent any body part.
During this test I used the side of a long piece of charcoal. similar to using both hands. I rotated the charcoal as though it was the length of the leg. capturing the lower and upper points of the joint creating some interesting volumes. I also tried breaking down into a stick figure and drawing as though it was frames.
Drawing the body fairly fully at constant intervals created a nice sense of timing with more drawings during slower motion and less during the faster movements.