Friday, December 3, 2010

Congruency of Biceps

This illustration is from lecture blackboard notes from the Artistic Anatomy class that I teach at the Barrett Art Center in Poughkeepsie

A third Class Lever in Diagram

The Biceps Brachii of the upper arm and the Biceps Femoris of the upper leg share a offer an interesting shared function. The contraction of both muscles result in the action exemplified by a third class lever- where the Resistance ( gravitational vector or weight), lies between the Fulcrum(joint) and the Effort (Muscular contraction). Like a crane, this lever facilitates the maximum concentration of force against gravity, and is the primary force in trans-location of the body. What is fascinating is that the both muscle groups are located anterior and posterior of each other. Evolving from quadriped animal ancestors whose translocation imperative was the use of limbs oriented in the same direction for running, into an upright standing biped whose survival imperative was increased by their ability to grasp objects,the upper limbs migrated to face the front. As a result of this, the rotation of the thumb occurred- the first metacarpal of the thumb rotating along with its corresponding wrist bone, out of plane with the other four metacarpals. It would also appear that this entire process occurred after the earliest animal ancestor of man still had some use for a minimally grasping foot since the human foot shows evolution away from any grasping imperative. The tarsal bones have evolved to distribute weight more efficiently therebye resulting in fewer bones in the ankle. If this earliest ancestor had perfected its running imperative to survive, the hand as a grasping mechanism and the entire bipedal strategy would never have occurred.

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