What occurs during muscle fatigue when oxygen supplies in muscles are low?

During muscle fatigue with low oxygen supplies, the body shifts from aerobic to anaerobic metabolism to continue generating energy. This leads to the production of lactic acid, which accumulates in the muscles, causing discomfort and reducing muscle function. Additionally, the depletion of glycogen stores and the accumulation of metabolic byproducts contribute to the sensation of fatigue and decreased performance. Ultimately, these changes impair the muscle's ability to contract effectively.