The Elbow Kinetics Flashcards
What effect do the factors of location of muscles, position of forearm, magnitude of loads and speed of motion have on the function of the brachialis?
Brachialis–under bicep, crosses anterior elbow. From humerus to ulna. Moves the ulna (which moves everything else.) Only moves ulna and flexes forearm. Works if there is load or no load, fast/slow. (This muscle will always work in forearm flexion due to its location.)
Explain the significance of forearm position in testing the elbow flexor muscles with MMT
Take advantage of forearm position to isolate out the forearm flexors because brachialis is always working.
Mid-range…brachioradialis/brachials.
Supinated…bicep/brachialis.
What effect do the factors of location of muscles, position of forearm, magnitude of loads and speed of motion have on the function of the bicep?
Bicep–attaches to radius. Radius can flex and sup/pranate. The bicep will try to move the radius in all of its joint movements. Position effects bicep…Least active in pronated position. Does not turn off. If loaded while in pronation, the bicep will activate. Works in mid-position too. Speed of moation increases activity of bicep. Slow means no work unless there is a load.
What effect do the factors of location of muscles, position of forearm, magnitude of loads and speed of motion have on the function of the brachioradialis?
Brachioradialis–line of force stabilizes radius ito humerus. Only active in mid-forearm position and pronated. Doesn’t work if no load. Slow with load, it works. Fast with no load, it works.
Explain how shoulder extension by the posterior deltoid acts as a synergy for elbow flexion/flexors.
It helps the length/tension relationship of crossbridges for actin/myosin. As one curls a barbell etc., it is natural for the posterior deltoid to pull the arm into extension. This lengthens the long head of the bicep which helps the length/tension relationship to generate tension in the flexors.
Describe the recruitment pattern of the elbow extensors.
Anconius is 1st., then medial head of triceps, lateral head, long head. Only use as much muscle as demand requires.
Specifically explain how the anterior deltoid works synergistically with the tricep during a forward push and how the tricep functions synergistically for the bicep during forearm supination.
It helps lengthen the tricep muscle. The tricep extends the elbow and the deltoid flexes the shoulder to lengthen the arm anteriorly.
Bicep supinates and flexes the arm. When turning a screw into a board, the tricep stops the bicep from flexing and isolates supination movement.
Compare and contrast the conditions under which the supinator and bicep functions to supinate the forearm.
Supinator functions all the time to supinate the forearm.
When the elbow and shoulder are at full extension, the bicep’s line of pull is in translation and only the supinator supinates. If bicep is in shortest position (elbow and shoulder flexion), only supinator can supinate.
Compare and contrast the bicep component forces of the resultant force vector during supination considering the elbow at 90 degrees vs 30 degrees. In which position does the bicep contribute more to the supination function and why?
Bicep works best as a supintor at 90 degrees. Puts the bicep in the best position to be able to spin the radius. at other angles, part of the muscle is dedicated to translation.
What elbow position might one use to isolate the supinator for MMTing and why?
Either fully extend or fully contract the bicep so that it cannot contribute to supination. Applies to pretty much any muscle.
Other than pronation, what would be the effect of the pronator teres at the proximal radioulnar joint AND what would be the effect of the pronator quadratus at the distal radioulnar joint? Explain how the effect is possible based on a breakdown of the resultant force vector of each muscle into its component. forces.
Force analysis shows that the pronator teres has a large translatory component.
Pronator Quadratus pronates, and it compresses the radius into the ulna.
Both muscles have a stabilizing roll.
What does compression indicate?
Compression always means stabilization.
