factors that contribute to muscle fatigue

MUSCLE FATIGUE :- 

It refers to the decline in muscle force generated over sustained periods of activity or due to pathological issues. Different factors that contribute are:-

• Lactic acid accumulation: It is a byproduct of anaerobic respiration which strongly contributes to muscle fatigue. In aerobic respiration, pyruvate produced by glycolysis is converted into ATP in mitochondria via Krebs cycle. With insufficient oxygen, pyruvate accumulates in the muscle fiber in the form of lactic acid. This reduces the pH, making it more acidic and producing the stinging feeling. this inhibits anaerobic respiration, inducing fatigue.
• Ion Imbalance:  Contraction of a muscle requires Ca2+ ions to interact with troponin, exposing the actin binding site to the myosin head. With extensive exercise, the osmotically active molecules outside of the muscles are lost through sweating. This loss changes the osmotic gradient, making it more difficult for the required Ca2+ ions to be delivered to the muscle fibers. this sometimes leads to muscle cramps. 
• Metabolic Fatigue:-  Depletion of required substrates such as ATP or glycogen. Accumulation of Mg2+ ions or reactive oxygen species can also induce fatigue.