Characteristics of Skeletal Muscle Fiber Types in the Miniature Pig and the Effect of Training

The fiber types present in miniature pig skeletal muscle were determined with enzyme histochemical techniques. Three distinct fiber types were found: a fast white fiber, a fast intermediate fiber, and a slow red fiber. The fiber types found in miniature pig (large mammal) skeletal muscle were different from those in rat (rodent) skeletal muscle where the fiber types are classified as fast white, slow intermediate, and fast red. The fiber type distribution in miniature pig skeletal muscle was not altered by either an endurance or sprint running program, despite physiologically measurable training effects. It is concluded that enzyme histochemistry is a good qualitative tool for assessing the fiber types present in a muscle but lacks the sensitivity to measure or quantitate changes due to training.