Muskelarkitektur

Muskelarkitektur, or muscle architecture, refers to the arrangement of muscle fibers within a skeletal muscle relative to its line of action. Key architectural features include fascicle length (the length of the muscle fiber bundle), pennation angle (the angle between muscle fibers and the force-generating axis), physiological cross-sectional area (PCSA), and muscle volume. Together these properties determine how much force a muscle can generate and how quickly it can shorten.

Fascicle length largely constrains shortening velocity and excursion, while PCSA relates to peak force. Pennation angle allows more fibers to be packed into a given volume, increasing PCSA at the cost of some shortening velocity. The architectural gear ratio describes how changes in angle and tendon length affect apparent shortening during contraction. Muscle architecture is variable across muscles, individuals, and species, and changes with growth, training, immobilization, and aging.

Measurement typically uses imaging techniques such as ultrasound to estimate fascicle length and pennation angle, or MRI and diffusion tensor imaging for broader structural information. Demands of activity influence remodeling: resistance training tends to increase PCSA and sometimes pennation, while endurance training may have smaller effects on architecture. Immobilization or unloading can reduce fascicle length and PCSA, reducing force and velocity.

Understanding muscle architecture helps explain differences in strength, power, and injury risk, informs rehabilitation strategies, and guides athletic training and biomechanical modeling.