Within skeletal muscle there are three types of fiber: Type I. Type I fibers are also known as slow twitch fibers. They are red in colour due to the presence of large volumes of myoglobin and so oxygen and high numbers of Mitochondria.or this reason the muscles containing mainly type I fibers are often postural muscles such as those in the neck and spine due to their endurance capabilities Also, athletes such as marathon runners have a high number of this type of fiber, partly through genetics, partly through training. Type IIa.
types of IUDs. 1  Hormonal There are four hormonal IUDs available in the U.S.âMirena, Skyla, Liletta, and Kyleena. 2  Non-Hormonal There's only one IUD without hormones available in the U.S. It's called ParaGard and it's made of plastic and a small amount of natural, safe copper.
The IUD is a small, T-shaped flexible device that is inserted into the uterus. The Mirena IUD continuously releases a small amount of the progestin levonorgestrel and is effective for 5 years. Skyla works the same way as Mirena but only lasts for 3 years.