Biomechanics: Reflection 1

Brushing my teeth is the very first thing that I do every single morning. Whenever I stand in front of my sink, my knees are extended, my shoulder is flexed, my forearm is supinated and my elbow is extended to wet the toothbrush. After wetting the toothbrush, my elbow and shoulder flex to put the toothbrush in my mouth,  the forearm is pronated, while my knees and wrist are extended. The movements that are occurring in this scenario (flexion and extension) are in the sagittal plane, which happens in the frontal axis. During pronation and supination, the action is in the transverse plane and the vertical axis.

The osteokinematics of the arm which occur at the elbow are in an open kinematic chain because the distal segment is free to move about. While brushing your teeth, the prime mover (agonist) is the biceps brachii, brachialis, and the brachioradialis, where they perform a concentric contraction. The antagonist, in this case, would be the triceps brachii. In terms of arthrokinematics, the convex humerus allows the concave ulna to glide and roll in the same direction.