Muscle weakness in generally described as the reduced strength of the muscle. It can happen in one muscle, a group of muscles, one or more limbs, half body or may involve full body sometimes. When full effort even does not produce the normal muscle movement, it is termed as muscle weakness. It is different from the muscle fatigue, which happens due to lack of energy or strength. Muscle fatigue is often termed as subjective weakness whereas true muscle weakness is termed as objective weakness. Muscle moves when brain sends certain signals through spinal cord and nerves to the muscles. If any injury has happened to brain, spinal cord or the nerves, it results in the weakness of muscle.
Weakness can be caused by a variety of disorders.
- Neurological disorders: Loss of blood supply to any part of nervous system damages it. It results in the neurological disorders and eventually in muscle weakness.
- Metabolic disorders: Increased levels of parathyroid hormone or decreased levels of sodium, potassium or calcium cause muscle weakness.
- Muscle diseases: Those muscle diseases which causes decrease in tone of muscles also results in muscle weakness.
- Poisoning: Botulism and shellfish poisoning also causes muscle weakness.
- Other diseases: Reduced hemoglobin level in the body, polio and defects in defence system of body also causes muscle weakness.