<P> Muscle fatigue is the decline in ability of a muscle to generate force . It can be a result of vigorous exercise but abnormal fatigue may be caused by barriers to or interference with the different stages of muscle contraction . There are two main causes of muscle fatigue: the limitations of a nerve's ability to generate a sustained signal (neural fatigue) and the reduced ability of the muscle fiber to contract (metabolic fatigue). </P> <P> Muscle cells work by detecting a flow of electrical impulses from the brain which signals them to contract through the release of calcium by the sarcoplasmic reticulum . Fatigue (reduced ability to generate force) may occur due to the nerve, or within the muscle cells themselves . </P>

What is the most common reason for muscle fatigue