Calf soreness and weakness feeling tired has more reasons, may be related to hypothyroidism, electrolyte disorders, polymyositis and so on. 1. Hypothyroidism: It is caused by low level of thyroid hormone, which leads to reduced nerve and muscle excitability, slow muscle contraction, and weakness. 2. Electrolyte disorders: most often occur after acute gastroenteritis, usually accompanied by frequent vomiting and diarrhea. This leads to a large loss of electrolytes and body fluids and electrolyte disorders, causing weakness in the legs. 3. Polymyositis: widespread inflammatory lesions of skeletal muscle that may be caused by a variety of reasons such as heredity and infection, necrosis of skeletal muscle fibers and lymphocyte infiltration can also lead to calf weakness. Calf soreness and weakness can also be seen in other causes, it is recommended to consult a doctor in a timely manner, follow the doctor’s instructions for further examination, with the help of the doctor to clarify the cause, and targeted treatment or therapy.