The Science Journal of the Lander College of Arts and Sciences


The purpose of this paper is to investigate the adaptations that occur in human skeletal muscle in response to endurance and resistance exercises. The advances made in science over the past several decades increased the number of methods available for the classification of muscle fibers, resulting in many fiber type classes and their corresponding characteristics. This allows for the tracking of changes that occur within the muscle fibers. The heterogeneous collection of fiber types found within a muscle allows for its dynamic nature. Myosin form expression varies according to the muscle’s changing functional demands. In response to endurance training, muscle fibers adapt by changing in composition, converting between type IIB and type IIA (i.e. the fast to slow direction). In response to resistance training, muscle fibers undergo both fiber-type shifting and hypertrophy. This muscle plasticity allows for the physiologic changes that take place in athletes and in physical therapy patients. The research available allows for the designing of interventions specific to increasing one’s endurance or power.