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Skeletal Muscle
Published in Nassir H. Sabah, Neuromuscular Fundamentals, 2020
Skeletal muscle architecture refers to the arrangement of fibers in a muscle and has an important bearing on muscle function. Whereas the muscle fibers in fascicles (Figure 9.1) are parallel to one another, the fascicles themselves can have different orientations relative to one another and to tendons, which lie on the line of action of the muscles. There are basically four different muscle architectures: Parallel muscles, in which the fascicles run parallel to the line of action of the muscle and generally extend from one end of the muscle to the other (see Section 10.4). A good example is the sartorius muscle, a ribbon-shaped muscle, of about 40 cm length in humans, that runs obliquely along the thigh and is involved in flexion of the knee as well as flexion, abduction, and lateral rotation of the hip. Parallel muscles could also be spindle shaped, or fusiform, as in the biceps brachii muscle of the upper arm.Convergent muscles, in which the fascicles extend over a fairly wide area at one end of the muscle and converge to a common attachment site at the other end, as in the pectoralis muscles of the upper chest. The distinguishing feature of a convergent muscle is that it can pull in different directions, depending on the parts of the muscle that are activated.Pennate muscles, in which the fascicles are oblique to the force-generating axis of the muscle as a whole. In unipennate muscles, the muscle fibers are oriented at a single angle relative to the force-generating axis, this angle being generally between 0°–30°. An example is the extensor digitorum longus muscle of the leg, which extends the small toes and dorsiflexes the foot. Typically, the fascicles extend from an aponeurosis on one side to a tendon on the other side, as illustrated diagrammatically in Figure 9.9a. In bipennate muscle, the fascicles converge toward a central tendon from both sides (Figure 9.9b), as in the rectus femoris, a large muscle in the quadriceps group of muscles that extend the knee. In multipennate muscle, the fascicles are oriented at several angles relative to the axis of force generation (Figure 9.9c), as in the deltoid muscle that controls shoulder movement. The important characteristics of pennation are discussed in Section 10.4.Sphincter muscles, which are circular muscles that surround an opening or recess and perform some controlling function upon contracting. An example is the orbicularis oculi muscle around the eye, which closes the eyelids and whose contraction can be involuntary, as in sleeping and blinking.
Immediate effect of a wearable foot drop stimulator to prevent foot drop on the gait ability of patients with hemiplegia after stroke
Published in Assistive Technology, 2021
Ji-Su Park, Sang-Hoon Lee, Won-Gyu Yoo, Moon-Young Chang
In particular, contraction of the peroneus tertius and the extensor digitorum longus through stimulation of the deep peroneal nerve causes ankle dorsiflexion as well as extension of the toes. As a result, claw toe is prevented, so it is possible to form a wider base of support, which provides a more comfortable and safe feeling to the patient when walking. In addition, FDS is clearly a potential positive contributor to walking ability and fall prevention because it provides more sensory input from the ground directly to the sole of the foot than the AFO. It is known that tactile stimulation from sensory inputs improves the postural schema (Longo, Azañón, & Haggard, 2010).