ORIGINAL COMMUNICATION Fiber Type Composition and Maximum Shortening Velocity of Muscles Crossing the Human

A study of the fiber type composition of fourteen muscles spanning the human glenohumeral joint was carried out with the purpose of determining the contri-bution of fiber types to overall muscle cross-sectional area (CSA) and to esti-mate the maximum shortening velocity (Vmax) of those muscles. Muscle biop-sies were procured from 4 male cadavers (mean age 50) within 24 hr of death, snap frozen, mounted, and transversely sectioned (10 lm). Slides were stained for myofibrillar ATPase after alkaline preincubation. Photoimages were taken of defined areas (100 fibers) using the Bioquant system, and fiber type and CSA were measured from these images. Staining for mATPase produced three different fiber types: slow-oxidative (SO), fast-oxidative-glycolytic (FOG), and fast-glycolytic (FG). On average, the muscle fiber type compositio