For perceived muscle weakness, asthenia has been described as the feeling of weak or tired muscles in the absence of muscle weakness, that is the muscle can generate a normal amount of force but it is perceived as requiring more effort.

General asthenia occurs in many chronic wasting diseases (such as tuberculosis and cancer), sleep disorders or chronic disorders of the heart, lungs or kidneys, and is probably most marked in diseases of the adrenal gland. Moreover, asthenia can be a symptom of mast cell activation syndrome (MCAS).