Applied anatomy and kinesiology, the mechanism of muscular movement . OIDPROCESS STYLOIDPROCESS STYLOID IPROCESS POSTERIORBORDER BSTYLOID?PROCESS Fig. 67 Fig. 68 Figs. 67 and 68.—The radius and ulna. (Gerrisb.) the like; in all forcible supination, as in turning a screw-driver toturn a screw in with right hand or out with left; when the armis raised sideward it seems to contract during a horizontal swingof the arm forward, but this may be done to protect the elbowagainst injury from overextension, which the movement tends toproduce. BICEPS 121 When the biceps is stimulated by electricity it fl
Applied anatomy and kinesiology, the mechanism of muscular movement . OIDPROCESS STYLOIDPROCESS STYLOID IPROCESS POSTERIORBORDER BSTYLOID?PROCESS Fig. 67 Fig. 68 Figs. 67 and 68.—The radius and ulna. (Gerrisb.) the like; in all forcible supination, as in turning a screw-driver toturn a screw in with right hand or out with left; when the armis raised sideward it seems to contract during a horizontal swingof the arm forward, but this may be done to protect the elbowagainst injury from overextension, which the movement tends toproduce. BICEPS 121 When the biceps is stimulated by electricity it flexes the elbowand supinates the forearm at the same time, and the question arises,How does one perform these two movements separately and usethe biceps in both ? Anyone can easily demonstrate on his own armthat he can flex the elbow without difficulty with the forearm inany position from extreme pronation to extreme supination, andcan supinate the forearm whilejthe elbow is in any position betweencomplete flexion and complete extension, the biceps acting in all. Fig. 69.—The biceps in action. cases. Evidently the will can do nothing directly to cause one ofthe two movements separately, for it can do no more than stimu-late the muscle to action. The reader can find a clue to the problem by making the follow-ing easy test: stand in front of the person who acts as subject andfacing him, with your left hand grasping his upper arm loosely withthe finger-tips resting on the triceps and the thumb on the biceps, 122 MOVEMENTS OF ELBOW AND FOREARM so as to be able to detect any contraction of either; now have himsupinate the forearm strongly while with your right hand yougrasp his hand to resist the movement he makes, and notice howboth his biceps and triceps contract at the same time. Evidentlythe biceps is acting to supinate the forearm, but why is the tricepsworking? Beevor, who first explained the matter, says that thetriceps acts to prevent the elbow from being flexed by the ac
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