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The muscle cross-sectional area (blue line in figure 1, also known as anatomical cross-section area, or ACSA) does not accurately represent the number of muscle fibers in the muscle. A better estimate is provided by the total area of the cross-sections perpendicular to the muscle fibers (green lines in figure 1).
The longitudinal axis is the force generating axis of the muscle and pennate fibers lie at an oblique angle. As tension increases in the muscle fibers, the pennation angle also increases. A greater pennation angle results in a smaller force being transmitted to the tendon. [9] Muscle architecture affects the force-velocity relationship.
Henneman’s size principle describes relationships between properties of motor neurons and the muscle fibers they innervate and thus control, which together are called motor units. Motor neurons with large cell bodies tend to innervate fast-twitch, high-force, less fatigue-resistant muscle fibers , whereas motor neurons with small cell bodies ...
For a pennate muscle, cosΦ is always less than 1, meaning that the distance ac is always shorter than the distance ab, thus the muscle fiber shortening is 'amplified' by a factor of 1/cosΦ. Architectural gear ratio , also called anatomical gear ratio (AGR) is a feature of pennate muscle defined by the ratio between the longitudinal strain of ...
The other coordinates can be obtained from vector addition [5] of the 3 direction vectors: e 1 + e 2, e 1 + e 3, e 2 + e 3, and e 1 + e 2 + e 3. The volume V {\displaystyle V} of a rhombohedron, in terms of its side length a {\displaystyle a} and its rhombic acute angle θ {\displaystyle \theta ~} , is a simplification of the volume of a ...
Muscle fibers can only contract up to 40% of their fully stretched length. [citation needed] Thus the short fibers of pennate muscles are more suitable where power rather than range of contraction is required. This limitation in the range of contraction affects all muscles, and those that act over several joints may be unable to shorten ...
A myofibril (also known as a muscle fibril or sarcostyle) [1] is a basic rod-like organelle of a muscle cell. [2] Skeletal muscles are composed of long, tubular cells known as muscle fibers, and these cells contain many chains of myofibrils. [3] Each myofibril has a diameter of 1–2 micrometres. [3]
The number of muscle fibers within each unit can vary within a particular muscle and even more from muscle to muscle: the muscles that act on the largest body masses have motor units that contain more muscle fibers, whereas smaller muscles contain fewer muscle fibers in each motor unit. [1]