Muscle weakness is a very common complaint experienced by many people. Therefore, the conditions that can cause concern are quite diverse. For example, muscle weakness can occur after a stroke. It also happens in a condition known as muscular dystrophy. Both of these lead to weakened muscles that can no longer handle normal physical strain. Muscle weakness is often caused by inactivity, aging, muscle injury, or pregnancy. It may also result from chronic illnesses such as diabetes or heart disease. Other potential causes include stroke, multiple sclerosis, depression, fibromyalgia, and chronic fatigue syndrome.
Decreased Activity
Reduced muscle activity is one of the most common causes of muscle weakness. It often occurs due to a sedentary lifestyle. When muscles are not used, muscle fibers are partly replaced by fat. However, muscles can be strengthened at any age through regular exercise.
Aging
As our muscles age and weaken, they tend to lose strength and volume. Although many people see this as a natural part of aging, the inability to do what you once could when younger can be concerning. Nevertheless, physical activity is beneficial at any age, and with the right exercise routine, it is still possible to improve muscle strength.
Infections
Infections and illnesses are among the most frequent causes of temporary muscle fatigue. This usually occurs when muscles become inflamed. While recovery is typically quick, if the inflammation is severe (as in cases of severe flu), weakness can persist for a long time. Sometimes, this can lead to chronic fatigue syndrome. Other infections that may cause this include the flu, Epstein-Barr virus, HIV, Lyme disease, and hepatitis C.
Pregnancy
High levels of steroids in the blood during and shortly after pregnancy may cause a feeling of muscle fatigue, along with iron deficiency. While this is a normal condition during pregnancy, the risk of muscle weakness can be reduced through safe and gentle exercise during pregnancy.
Chronic Diseases
Many chronic illnesses can lead to muscle weakness, including:
Peripheral artery disease
Diabetes
Heart disease, especially heart failure
Chronic lung disease
Chronic kidney disease
Anemia
Chronic pain
Anxiety
Depression
Muscle Damage from Injury
There are many ways muscles can be directly injured. The most obvious are injuries such as sports trauma, strains, and sprains. Any muscle injury involves internal bleeding from torn muscle fibers, followed by swelling and inflammation. This reduces muscle strength. Local pain is the main symptom, but weakness may also occur.
Sleep Disorders
Problems that disrupt or reduce sleep — such as anxiety, depression, chronic pain, restless leg syndrome, or shift work — can lead to increased overall fatigue, including muscle fatigue.