Body aches and fatigue can be caused by overwork, colds, polymyositis and other factors. 1. Overexertion: strenuous exercise or heavy physical labor may lead to the accumulation of lactic acid metabolites in the muscles, which will lead to the symptoms of aches and pains and fatigue, which may improve on their own after reasonable rest. 2. Cold and flu: usually associated with viral infections, can cause muscle aches and pains as well as symptoms of fatigue, which may be accompanied by fever, sneezing, runny nose, cough and other symptoms. 3. Polymyositis: It may be related to genetic and viral infections, which can cause muscle pain, accompanied by weakness, lethargy, fever and other symptoms, and in severe cases, it can lead to respiratory failure, heart failure and other complications. These are only some of the common causes. If symptoms persist or recur, consult a doctor. After a clear diagnosis, follow the doctor’s instructions to standardize the treatment.