SIZE AND PROPORTION OF FIBER TYPES IN HUMAN MUSCLE FASCICLES

Size and distribution of 2 histochemical types of muscle fibers within the human muscle fascicle were investigated. Cryostat sections (ATPas e, pH 9.4) were studied from 15 quadriceps femoris, 15 biceps brachii and 15 deltoid muscles taken at autopsy from 12 males and 9 females wh o had no history of neuromuscular disease. The number and the lesser d iameter of type 1 and type 2 fibers were counted and percentage and me an diameter of the 2 types of fibers were calculated separately for pe riphery and interior of randomly selected fascicles. The results showe d that a progressive age-related reduction of the diameter of type 2 f ibers is observed and the predominance of type 2 fibers in the periphe ry is a constant finding in all muscles studied, regardless of sex and age.