Upper limb muscle volumes in adults

Muscle force-generating properties used in models are derived from measurements of muscle architecture, such as volume, cross-section, and fiber length. While the peak force a muscle can produce is related to its physiological cross-sectional area, several studies of muscle architecture have shown that muscle volume is an excellent predictor of joint moment-generating capacity, and is an important parameter for evaluating strength in the upper limb and for model development. Researchers have classically relied on dissection of cadavers to assess architectural properties of the muscles of the upper limb, including muscle volume, fiber length, sarcomere length, and pennation angle. Medical imaging approaches, including computed tomography, magnetic resonance imaging, and ultrasound have also been used to assess muscle force-generating properties in living subjects. In this review, the strengths and weaknesses of these approaches for assessing muscle volume in the upper limb are discussed. The volumes of muscles in the upper limb as measured by a number of researchers are summarized and compared. A study in which a magnetic resonance imaging approach is used to assess the muscle volumes of all the muscles crossing the shoulder, elbow, and wrist in living subjects is highlighted. It has been shown that the distribution of muscle volume in the upper limb is highly conserved across these subjects with a threefold variation in total muscle volumes (1,427-4,426 cm³). The studies discussed in this review provide normative data that form the basis for investigating muscle volumes in other populations, and for scaling computer models to more accurately represent the muscle volume of a specific individual.