The iris dilates and constricts thus, regulating

1. body tissue that is connected to and moves the bones in the body hypertrophy 2. the ability of a muscle to move a weight repeatedly, or for an extended period of time tendon 3. the increase in the size of a muscle fiber in response to resistance training muscle strength 4. the most amount of weight a muscle can move at a single time skeletal muscles 5. the decrease in the size and strength of a skeletal muscle when it is not used atrophy 6. strong body tissue that connects the muscles to the bones muscle endurance