develops from slow muscle cell ZFA:0009116 slow muscle fiber https://cellxgene.cziscience.com/cellguide/CL_0000189 A muscle cell that develops tension more slowly than a fast-twitch fiber. Slow muscle cells, as the name implies, are a type of muscle cell well known for their slow contractile speed. They are also referred to as type I, slow-twitch, or red muscles because of their high myoglobin content which gives them a dark, reddish appearance. These cells are predominantly found in the postural muscles of the body, such as those in the back and lower limbs. A defining characteristic of slow muscle cells is their significant resistance to fatigue. This is largely due to their efficient oxidative metabolism, which allows them to continuously contract over extended periods without succumbing to fatigue. This extraordinary endurance is facilitated by a high concentration of mitochondria, which enables the efficient use of oxygen for energy production, and capillaries, which supplies the necessary oxygen and nutrients. Additionally, these cells have an abundant supply of myoglobin, a protein that stores and transports oxygen within the muscle cell, further supporting their aerobic metabolism. The primary role of slow muscle cells in the human body is to provide sustained, low-intensity contractions over a prolonged period. They are responsible for maintaining posture and providing stability, rather than delivering short, powerful bursts of activity. They play a pivotal role in supporting various physical activities such as standing, walking, or any form of exercise that requires endurance over speed. (This extended description was generated by ChatGPT and reviewed by the CellGuide team, who added references, and by the CL editors, who approved it for inclusion in CL. It may contain information that applies only to some subtypes and species, and so should not be considered definitional.) slow muscle myoblast extrafusal muscle fiber