Brief periods of generalized weakness are common, especially after a strenuous workout or a stressful emotional situation, and usually they just mean that you have overexerted yourself. Generalized weakness is not a cause for concern as long as you are able to move all parts of your body and complete your normal daily activities, even if you have to work a little harder to get things done.
Weakness that does not have an obvious cause, such as overexertion or a viral or bacterial illness, or that does not get better or go away is more of a concern.
Sudden, severe generalized muscle weakness may be caused by a serious problem, such as coronary artery disease or heart failure. Weakness that is rapidly getting worse may be caused by poisoning, such as botulism, or a nervous system problem, such as a stroke or a transient ischemic attack (TIA). Muscle weakness that comes on suddenly or is getting progressively worse requires a visit to a health professional.
On rare occasions, generalized muscle weakness is caused by another health problem, such as:
See your health professional if your generalized weakness is so severe that you cannot complete your normal daily activities.
WebMD Medical Reference from Healthwise