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.
It is also used to treat heavy menstrual bleeding. Mirena iud is a progestin intrauterine device (IUD). It may work in several ways. It may change cervical mucus to prevent the sperm from reaching the egg. It may also change the lining of the uterus to prevent implantation in the uterus if an egg is fertilized.