Muscle wasting is a loss of muscle mass due to the muscles weakening and shrinking. There are several possible causes of muscle wasting, including certain medical conditions, such as amyotrophic lateral sclerosis.

The symptoms of muscle wasting depend on the severity of muscle mass loss, but typical signs and symptoms include:

  • reduced muscle strength
  • an impaired ability to perform physical activities
  • a decrease in muscle size

Diagnosis usually occurs after a medical history review and physical examination. The cause of muscle wasting is sometimes evident. In other instances, a doctor may need to perform additional tests to confirm a diagnosis.

Medical conditions that can cause muscle wasting include the following:

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A number of medical conditions can cause muscles to weaken.

Amyotrophic lateral sclerosis (ALS) is a progressive disease that affects nerve cells throughout the body.

Usually, the nerve cells in the brain and spinal cord send messages to the muscles to move.

In people with ALS, the nerve cells that control voluntary movement die and stop sending the signals that allow movement. Eventually, due to lack of use, the muscles atrophy.

Doctors do not know what causes ALS.

Learn more about ALS here.

Muscular dystrophy is a genetic condition that leads to progressive muscle weakness and muscle wasting.

There are several types of muscular dystrophy, which vary in their age of onset and specific symptoms.

Learn more about muscular dystrophy here.

Multiple sclerosis (MS) is a type of autoimmune disease that affects the myelin that surrounds the nerve fibers.

The condition causes damage to the nerves, which affects the muscles in turn. The damaged nerves lose their ability to trigger muscle movement, leading to atrophy.

The severity of the damage affects the rate of muscle loss.

Learn more about multiple sclerosis here.

Spinal muscular atrophy is a condition that is similar to muscular dystrophy.

The disease is genetic and occurs due to a loss of motor neurons, which are cells that control the muscles. The muscles in the body gradually weaken.

Although it weakens most of the muscles in the body, spinal muscular atrophy usually affects the muscles closer to the center of the body most severely.

Learn more about spinal muscular atrophy here.

Some other causes of muscle wasting, which are not medical conditions in themselves, include:

Inactivity for extended periods

Prolonged inactivity, such as bed rest, can lead to a loss of muscle mass. Bed rest may be necessary due to injuries or illnesses that leave a person unable to move.

According to research, muscle wasting can develop within 10 days in healthy older adults on bed rest. Due to the muscle wasting, a 40% decrease in muscle strength can occur within the first week.

Malnutrition

People with malnutrition have a significantly inadequate nutritional intake, and this can cause muscle loss, leading to muscle wasting.

Malnutrition has a variety of possible causes, including anorexia nervosa, cancer, and persistent nausea.

Aging

Muscle loss occurs gradually due to aging.

The authors of a 2013 study noted that significant changes to leg muscle mass occur after the age of 50 years when a muscle loss of 1–2% a year is typical.

They also highlighted research showing that between 20 and 80 years of age, the average person loses 35–40% of the muscle mass in their legs.

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Physical therapy may help prevent further muscle wasting.

Getting treatment for muscle wasting is vital for a person's overall well-being.

Muscle wasting occurs with many types of illness and disease. According to research from 2017, muscle wasting contributes to a worse prognosis in diseases such as heart failure, sepsis, and cancer.

Treatment may, in part, depend on the underlying condition leading to muscle loss. In some cases, treating the illness may prevent further muscle wasting and help reverse the condition.

Additional treatment options may include:

Exercise

Exercise to build strength is one of the main ways to prevent and treat muscle wasting. The type of activities that doctors recommend will depend on the cause of atrophy. For example, certain underlying conditions may limit specific exercises.

Focused ultrasound therapy

Focused ultrasound therapy is a relatively new treatment for muscle wasting. It involves directing beams of high-frequency sound waves at specific areas on the body. The sound waves stimulate muscle contraction, which may help decrease muscle loss.

Nutritional therapy

Proper nutrition helps the body build and retain muscle. Adopting a diet that provides sufficient calories, protein, and other nutrients that promote muscle development may help treat muscle wasting.

Physical therapy

Physical therapy may involve various techniques to prevent muscle wasting. Therapists may recommend certain exercises depending on the person's condition.

Physical therapy is also helpful if a person is on bed rest. Therapists may perform passive exercises if an individual is unable to move. This type of exercise involves the therapist moving the legs and arms to exercise the muscles.

Muscle wasting involves muscle loss or atrophy and usually happens gradually. It can occur because of a variety of conditions, including ALS, muscular dystrophy, and MS.

As muscle wasting can affect a person's strength and their ability to perform everyday activities, it can greatly reduce their quality of life.

Treating the condition as soon as possible may prevent or slow significant muscle loss. Anyone who thinks that they may have muscle wasting should see a doctor.

In some cases, it is possible to reverse muscle wasting, but it may take time. When muscle wasting is not reversible, treatment may at least slow the loss of muscle. Treatment may include a combination of exercises, nutritional changes, and physical therapy.