Biomechanics of Movement: The Three Classes of Levers

Biomechanics refers to the study of the mechanical principles of living organisms, particularly their movement and structure. In the human body this is known as kinesiology.

Most movements of the musculoskeletal structure are determined by the three classes of levers.

Levers are classified by the relative positions of the fulcrum and the input and output forces. It is common to call the input force the effort and the output force the load or the resistance. This allows the identification of three classes of levers by the relative locations of the fulcrum, the resistance and the effort:

 Class 1: Fulcrum in the middle: the effort is applied on one side of the fulcrum and the resistance on the other side, for example, a seesaw, a crowbar or a pair of scissors. Mechanical advantage may be greater or less than 1.

Class 2: Resistance in the middle: the effort is applied on one side of the resistance and the fulcrum is located on the other side, for example, a wheelbarrow, a nutcracker, a bottle opener or the brake pedal of a car. Mechanical advantage is always greater than 1.

Class 3: Effort in the middle: the resistance is on one side of the effort and the fulcrum is located on the other side, for example, a pair of tweezers or the human mandible. Mechanical advantage is always less than 1.

Action of the Head and Neck

The Action of the Head and Neck

This is a schematic by Al Dorne, that illustrates how these structural vertical and horizontal bisecting ellipses, what I like to call the Medial Line and the Mask overlap and converge as the head rotates in space.

Visualizing the Head in 3 dimensions

Visualizing the Head in 3 dimensions

This is a compendium to my Drawing the Head Workshop which was held at the Woodstock School of Art on May 8th and 9th 2018. I used as a syllabus, elements of the Famous Artists Course 1957 version. I believe the illustrations and text are by Albert Dorne who along with Norman Rockwell founded the Famous Artist Corse.

The most important thing in my opinion about drawing the head is in visualizing its volume. These drawings beautifully illustrate how the vertical medial line bisects the head bi-laterally, into two mirror halves. In addition, the horizontal bisecting lines describe the line of the eyes, nose level, and mouth on the egg- like volume of the head and appear as horizontal ellipses, or concentrics.

Planes of the Head

Andrew Loomis Planes of the Head

From my workshop at the Woodstock School of Art

Here is Andrew Lommis' version of the Planes of the Head. There are many versions of the planar head which exist among them: the Asaro head, the Bridgeman head, etc. and I'll post versions of these here.  What these heads all have in common is that the artist is attempting to simplify the skull into more easily interpreted geometric planes. By simplifying the geometry, it enables the artist to better visualize how the skull occupies space and how light falls across it. The variations in the planarity among these artists interpretations reflect these artists own visualization of the skulls volumes.

Drawing the Head

Drawing the Head

This is a compendium to my Drawing the Head Workshop  which was held at the Woodstock School of Art on May 8th and 9th 2018. I used as a syllabus, elements of the Famous Artists Course 1957 version. I believe the illustrations and text are by Albert Dorne who along with Norman Rockwell founded the Famous Artist Corse.

I've added my own observations to this course outline, which rely explicitly on the Medial Line as being the foundation from which drawing the head becomes much easier.