This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1917 edition. Excerpt: ...of the fact that the rotation of the tibia would increase its tension if the tone of the muscle were not diminished by nervous influence. We have noticed that the rectus femoris and the hamstring muscles reach past two joints--the hip and knee; this fact has led to their being called "two-joint muscles ...
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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1917 edition. Excerpt: ...of the fact that the rotation of the tibia would increase its tension if the tone of the muscle were not diminished by nervous influence. We have noticed that the rectus femoris and the hamstring muscles reach past two joints--the hip and knee; this fact has led to their being called "two-joint muscles" to distinguish them from the "one-joint muscles," which cross but one joint. Besides the actions we have studied thus far, and which may be called the individual actions of these muscles, the two-joint muscles of the thigh have a combined action due to their passing across the opposite sides of the two joints and which has been called their "tendinous action." When these two opposite sets of muscles are contracted enough to have considerable tension they serve to connect the two joints in the same way that a belt connects two pulleys, so that if you move one of them, the other moves with it. For example, if the hip is flexed by the psoas, iliacus, pectineus, and tensor (Fig. 96, A), which are one-joint flexors of the hip, the beltlike action of the two-joint muscles makes the knee flex also; this is because flexion of the hip puts extra tension on the hamstring group and lessens the tension of the rectus femoris, and the change of tension of the two opposing groups flexes the knee. Now while both joints are flexed, if the gluteus maximus, a one-joint extensor, contracts and extends the hip (Fig. 96, B), the change of tension on the belt will also extend the knee. These actions can be demonstrated with a model like that shown in Fig. 96, illustrating the general principle that the two-joint muscles of the thigh, when in contraction, exert a belt-like action on the hip and knee such that the two joints tend to...
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