There are 2 main reasons why the arm is unbearably uncomfortable at night. 1. Due to the presence of aseptic inflammatory lesions in the arm area, such as periarthritis of the shoulder joint, strain or strain on the surrounding musculature, this will form local inflammatory lesions, and at night when the arm is not fully relaxed and rested, muscle fatigue occurs again, inducing the accumulation of inflammation, leading to the formation of inflammatory edema, there will be 2, because of the cold during the night sleep, the muscle tissue structure will become more tense after the cold, and the local arterial blood supply will also decline, resulting in a decrease in local energy and nutrients as well as electrolyte supply, in addition to the venous return will also slow down, the lactic acid and other inflammatory metabolites formed in the muscles and surrounding soft tissues, can not be effectively metabolized in a timely manner, forming a buildup. The lactic acid and other inflammatory metabolites formed in the muscles and surrounding soft tissues are not metabolized in a timely and effective manner, forming a buildup, which will stimulate the peripheral nerves and make it easy for the symptoms of arm pain to occur.