A more gradual weakening can be related to several medical conditions. Regardless of the cause, loss of strength can contribute to increased risk of falls, decreased bone strength and weight gain.
Muscle movement starts as a signal from the brain, which travels down the spinal cord, along a nerve pathway and through the areas connecting the nerve and muscle junctions. Any disruption along the way can result in muscle weakness. Interference can be caused by:
Brain or spinal cord diseases: Cognitive decline, tremors, rigidity, muscle spasms and overly active reflexes are some signs of brain and spinal cord disease. Stroke or brain disorders such as Parkinson’s disease can cause weakness or difficulty coordinating or initiating muscle movement. An MRI can help with diagnosing many conditions that affect the brain or spinal cord.
Peripheral nerve damage: This can interrupt signals that the brain sends and can occur in many areas of the body. In addition to weakness, nerve damage can cause loss of feeling and decreased reflexes and muscle tone. When peripheral neuropathy is suspected, blood testing may be used to identify the underlying conditions, such as diabetes, inflammatory or genetic diseases or nutritional deficiencies.
Problems where nerves meet muscles: Diseases in this category include myasthenia gravis or Lambert-Eaton syndrome. They often cause weakness that increases with activity of a particular muscle group. Characteristics might include eyelid droop, double vision, slurred speech and difficulty swallowing and breathing.
Muscle disease: Weakness can be caused by muscle disease without the involvement of the nerves. Examples include inflammatory diseases such as polymyositis and dermatomyositis.
Other illness: Weakness is sometimes a sign of undiagnosed illness such as rheumatoid arthritis, lupus, Lyme disease or diabetes. Many other health conditions can contribute to feeling weak, including sleep problems, depression, pain and chronic illness.
Of all the causes of weakness, being unfit is the most common. Fortunately, nearly everyone can do some type of exercise to help maintain or regain muscle strength.
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