Muscle Atrophy (Muscle Wasting)

Types of muscle atrophy

Causes

Disuse

• bed rest or hospitalization. Muscle mass can fall noticeably within the first 1 to 2 weeks
• a cast or brace
• a sedentary lifestyle or desk job
• stroke or injury causing limited use of a limb

Nerve damage

• peripheral neuropathy, especially from diabetes
• pinched nerves in the neck or back
• nerve injuries
• amyotrophic lateral sclerosis and other motor neuron diseases
• spinal muscular atrophy
• polio and post-polio syndrome
• Guillain-Barré syndrome
• spinal cord injury

Aging

Sarcopenia, age-related loss of muscle mass and function, begins around age 30 to 40 and speeds up after 60 to 70. Inactivity, low protein intake and chronic disease accelerate it.

Illness and nutrition

• malnutrition and low protein intake
• cancer, heart failure, COPD, chronic kidney disease and HIV (cachexia)
• critical illness and intensive care
• alcohol use disorder

Muscle and hormone disorders

• muscular dystrophies
• inflammatory myositis
• Cushing syndrome and long-term steroid use
• overactive thyroid
• low testosterone

Symptoms

• one limb or area looking thinner than the other
• loss of strength, tiring easily
• difficulty climbing stairs, rising from chairs or lifting
• balance problems and falls
• with nerve causes: twitching, cramps, numbness or tingling

Diagnosis

• examination: comparing muscle bulk, measuring limb circumference, testing strength and reflexes
• blood tests: creatine kinase, thyroid function, inflammatory markers, vitamin D, nutritional markers
• nerve conduction studies and EMG: distinguish nerve from muscle causes
• imaging: MRI of muscles or spine
• muscle biopsy or genetic tests for suspected muscle disease
• sarcopenia screening: grip strength, chair-stand tests and walking speed

Treatment

Exercise

Progressive resistance training is the most effective treatment for disuse atrophy and sarcopenia. Use weights, bands or body weight 2 to 3 times a week, working major muscle groups, gradually increasing load. Walking, swimming and cycling support endurance. Balance exercises reduce falls. People who are recovering from illness or have heart or lung disease should start with supervised physical therapy.

Nutrition

• enough protein spread across meals. Older adults often need more than younger adults, commonly around 1.0 to 1.2 g per kg of body weight per day unless kidney disease limits it
• enough total calories
• vitamin D if low

Treating the cause

• early mobilization after surgery or illness
• physical and occupational therapy after stroke or injury
• treating neuropathy, nerve compression or hormone problems
• reducing steroid doses where possible
• disease-specific therapies for ALS, spinal muscular atrophy, myositis and others
• electrical muscle stimulation in some rehabilitation settings

Outlook

Disuse atrophy usually recovers well with exercise over weeks to months. Sarcopenia can be slowed and partly reversed with strength training and nutrition at any age. Neurogenic atrophy from permanent nerve damage or progressive disease may not reverse, but therapy maintains function.

Frequently asked questions

What causes muscle atrophy?

The most common cause is lack of use, from bed rest, a cast or inactivity. Other causes include aging, nerve damage, poor nutrition, chronic illnesses such as cancer and heart failure, steroid medicines, and muscle diseases such as muscular dystrophy or myositis.

Can muscle atrophy be reversed?

Disuse atrophy and age-related muscle loss can usually be reversed or improved with progressive strength training and adequate protein. Atrophy from permanent nerve damage or progressive diseases is harder to reverse, but exercise and therapy help maintain strength and function.

How quickly does muscle atrophy happen?

Muscle loss can begin within days of complete inactivity, and noticeable loss can occur within 1 to 2 weeks of bed rest or immobilization, especially in older adults. Neurogenic atrophy develops over weeks to months after nerve damage.

What is the difference between disuse and neurogenic atrophy?

Disuse atrophy results from not using healthy muscles and reverses with exercise. Neurogenic atrophy results from damage to the nerves supplying the muscle. It is often faster and more severe, may come with twitching or numbness, and depends on nerve recovery.

What are the warning signs of a serious cause of muscle wasting?

Seek medical advice for wasting with twitching, cramps or spreading weakness, rapid wasting of one limb, wasting with numbness, or wasting with unexplained weight loss, fever or night sweats. These may point to nerve disease, motor neuron disease or a systemic illness.