RELATIONSHIP BETWEEN MUSCLE-FIBER TYPES AND SIZES AND MUSCLE ARCHITECTURAL PROPERTIES IN THE MOUSE HINDLIMB

Skeletal muscle fiber and architectural properties both contribute to the functional behavior of a muscle. This study uses discriminant anal ysis and mathematical modeling to identify the structurally and functi onally significant properties. The architectural properties of fiber l ength, muscle length, and pennation angle are found to be the most str ucturally significant parameters, whereas fiber length, muscle length, and fiber type distribution are found to be most functionally determi ning. Architectural speed and fiber type do not, appear to be complime ntary (i.e., the architectural determinant of speed, fiber length, is not associated with fibers of high intrinsic velocity). However, there does seem to be a synergistic relation between the two property class es and force production. Muscles with large physiological cross sectio nal areas (PCSAs) tend to contain a greater proportion of larger, fast er fibers. Structurally or morphologically significant parameters are not always found to have a large functional effect. Pennation angle, t hough one of the most structurally significant variables, was found to have very little functional effect. (C) 1994 Wiley-Liss, Inc.