Adaptive Responses to Chronic Overloading in Different Regions of the Rat Plantaris Muscle

The purpose of this study was to investigate adaptive responses of proximal, middle and distal regions along the longitudinal axis in the rat plantaris muscle. Cross-sectional area (CSA), succinate dehydrogenase (SDH) and glycerophosphate dehydrogenase (GPD) activities of each typed fiber in individual regions were determined after a 5-week overloading by removal of synergists. CSA and SDH activities of each typed fiber in all regions were increased by overloading. GPD activities of type II fiber in all regions were increased by overloading. These results indicate that fibers of all regions in the plantaris muscle were recruited regardless of the type of fiber in chronic overloading