Sore and weak muscles may be caused by physiological factors such as lactic acid buildup from overexertion, colds, and side effects of some medications. 1. Physiological factors: due to overwork or excessive exercise, anaerobic metabolism produces lactic acid accumulation in the body, which cannot be metabolized within a short period of time, and muscle soreness and weakness may occur. 2. Colds and flu: mostly caused by viruses and other pathogens infecting the respiratory tract of the human body caused by local and systemic immune response, such as nasal congestion, runny nose, fever and muscle aches and weakness. 3. Rheumatic diseases: such as rheumatic polymyalgia, dermatomyositis, rheumatoid, rheumatoid arthritis and other diseases, which can cause muscle pain, weakness and other symptoms. Muscle pain and weakness may also have other causes, symptoms continue to be unrelieved it is recommended to go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, to give targeted treatment or treatment.