Main objective of this article is to define and discuss on Muscle Fibres. Here explain different muscle Muscle Fibres. Type I Muscle Fibres are those that are called the slow twitch or the sluggish oxidative fibers, which contain lots of myoglobin, mitochondria, and naturally, blood capillaries. These fibers have a very slow contraction velocity, thus they’re resistant to fatigue. Muscular tissues, being the useful elements of your body they tend to be, are composed of lean muscle fibers. These fibers tend to be long, multi-nucleated muscle tissues, also known as the myofibers.