I found it helpful to read Edgar Whitney here,

‘Learn to “see”, and describe from in the most elementary possible terms.  There are only four basic volumes:cubes (length and breadth can be different actually a right-angled parallelopiped – but lets save time and call it a cube), cylinders, cones, and spheres.  Your head is a cube.  Your upper arm is a cylinder.  Your lower arms and legs are cones…  An automobile is two modified cubes.

Do not think line as you draw.  Think-feel-be conscious of-describe volume.  Learn to see all volumes in terms of their simplest geometric equivalents the four mentioned above.” (1).

I really enjoyed drawing this.  Maybe more so because I was drawing my son.  As I went on, I think I became more fluid, and natural.  The drawings go from right to left as I am a left-hander and didn’t want to smudge the action! There was a shared sympathy with my model’s muscle fatigue that speed me into checking the balance, the proportions and movement quickly.  I felt a good 3-D form was described by the use of soft and hard pure graphite sticks, some torchon and finger work.

The feel and best sense of the pose, I feel grew with each pose.  My favourite would be the 6th drawing, with his left hand lifted right up.  This I felt had the best sense of the model.  Though I like bits of all the others, except for the first one, with him crouching.

1) Edgar A. Whitney, Complete Guide to Watercolor Painting. (Mineola: Dover Publications, Inc, 2001), 129