Biomechanics Blog Post #1

One movement that is a part of my morning routine is pouring a glass of milk. One of the movements after getting the milk out of the refrigerator is twisting the top off. Twisting off the cap requires grasping the cap and wrist adduction. Some tops are "pop off" and they require more supination of the forearm instead of wrist adduction. After the top is off I have to flex the elbow to lift the jug. While flexing the elbow, the shoulder is also abducting. In order to pour the milk into a glass the last movement is wrist adduction. This will instill the milk reaches the glass steadily.
    There are several joints being acted on while pouring a glass of milk. During elbow flexion, the sagittal plane, during shoulder abduction and wrist adduction, the frontal plane. There are also many axes being acted on during this movement. Elbow flexion is moving around the frontal axis, shoulder abduction and wrist adduction is occurring around the sagittal axis.
    The osteokinematics of the shoulder joint during the pouring is mainly shoulder abduction. I am abducting my shoulder to ensure the jug will be at the proper angle to pour into a glass. During shoulder abduction, it is visible that the humerus is moving further away from the midline of the body. In regards to the arthrokinematics during this movement, the head of the humerus glides inferiorly in the glenoid fossa. Because of the concave-convex rule, this allows the head of the humerus to stay in contact with the gleniod fossa.
   The prime movers of this movement are biceps brachii, brachialis, and brachioradialis during elbow flexion. Some other prime movers are the middle deltoid and supraspinatus during shoulder abduction. Lastly, during wrist adduction the prime movers are extensor carpi ulnaris and flexor carpi ulnaris. During elbow flexion, the biceps brachii, brachialis, and brachioradialis are contracting concentrically. Also, during shoulder abduction the middle deltoid is contracting concentrically because the muscle is shortening. Lastly, during wrist adduction, the extensor carpi ulnaris and the flexor carpi ulnaris are both contracting concentrically.
    Pouring a glass of milk is a vital part of my day. It has been interesting looking at all the movements involved in getting a glass of milk.