Alternate Names : Asthenia
Weakness is usually defined as a lack of or decrease in muscle strength. It is different from fatigue, which is a loss of energy.
What is going on in the body?
Weakness can be used to describe a mental and physical state in which someone doesn't have the muscle strength, for example, to walk. It is common and sometimes difficult to evaluate. Weakness has many causes.
What are the causes and risks of the condition?
Weakness has many causes that are best grouped into these categories:
muscle problems, such as deconditioning or a lack of exercise, muscle injuries or inherited muscle defects, such as muscular dystrophy
nerve problems, possibly nerve damage from injury or from toxins such as lead poisoning or alcohol dependence
nerve damage such as diabetic neuropathy
vitamin deficiencies, such as lack of vitamin B12
spinal cord injuries or other disorders
salt imbalances, such as a low sodium level, called hyponatremia, or a high potassium level, called hyperkalemia
brain problems, such as a stroke or a condition called Parkinsonism, which affects the ability to move
autoimmune disorders, which occur when people's immune systems attack their own bodies for unknown reasons. Some examples are multiple sclerosis, which causes inflammation and damage to the brain and myasthenia gravis, which causes muscle weakness that often gets worse toward the end of the day
hormone imbalances, such as low thyroid hormone levels, called hypothyroidism, or low adrenal hormone levels, called hypoadrenalism
any infection, especially infectious mononucleosis, flu, poliomyelitis, botulism or pneumonia
any serious diseases, such as congestive heart failure, cirrhosis, chronic renal failure, or cancer
psychiatric conditions, especially depression
chronic fatigue syndrome and fibromyalgia, two poorly understood conditions with no known cause that commonly make people feel weak and tired
Other causes are also possible. Sometimes, no cause is found.