 Dear students, in this topic, we shall discuss muscle fatigue, the prolonged and sustained strong contractions of the muscle lead to muscle fatigue, which we call as muscle fatigue. Skeletal muscles in this condition are no longer to contract optimally. Dear students, the muscle fatigue has physiological causes. This fatigue can occur in the neuromuscular junction or any of other contractile elements of the muscles. We shall discuss few of the reasons or causes of muscle fatigue. First, we shall discuss that the transmission of nerve impulses due to muscle activity as a result nerve impulses transmission diminishes, diminishes are slow. This happens because of ion imbalances happening due to the as a result impairment of excitability of the membrane occurs. So, when imbalances of ions, then the excitability of the membrane decreases and as a result nerve impulses conduction or transmission slow or diminish. Dear students, these ion imbalances, they happen because of improper functioning of sodium potassium pump. Sodium potassium pump functioning is because sodium potassium or calcium ion channels in activate are insensitive. If this is the cause of muscle fatigue, then there is a quick recovery within 30 minutes. Dear students, another physiological cause of muscle fatigue is the interruption in excitation contraction coupling. This happens due to impaired calcium release from cells internal resources that is from endoplasmic at the column. This recovery comparatively slower or 24 say 72 hours in this recovery. Dear students, the third cause of muscle fatigue is the interruption of blood flow to the contracting muscles. As a result, the nutrient and oxygen supply to the muscles is affected. This cause of muscle contraction, complete muscle fatigue, we call it complete muscle fatigue and it takes more time in recovery. Dear students, in three major causes, the factors in other fatigue contributors are accumulation of inorganic phosphates in the muscles. Then accumulation of hydrogen ions, which we call as metabolic acidosis, which affect metabolic processes. In addition, due to muscle cell contraction, the cells either depletion of glycogen or ATP in the energy resources, then muscle fatigue appears as a result. Dear students, the biggest contributor for muscle fatigue in the past was lactic acid accumulation. However, recent researchers have proved that this factor is not a cause of muscle fatigue. So now we do not consider this factor as a cause of muscle fatigue.