Nathan Lloyd says, “Your calf muscles are made up of two different types of muscle tissue: slow-twitch and fast-twitch. When you lift weights, your body uses both slow- and fast-twitch muscle fibers to perform the movement. When you engage in a strength training workout, you are increasing the amount of fast-twitch muscle fibers in your body—and thats good! Your calf muscles will look more toned and more defined as a result of this increase in fast-twitch muscle fibers.”