Introduction 

Do you ever feel like you’re physically wasting away? It sounds crazy, but it’s possible, it could be muscle atrophy. Muscle atrophy is the wasting of muscle and loss of strength and mass. Muscle atrophy causes muscle weakness, trouble balancing, walking, bone and joint problems, tremors, inflammation, and swallowing problems. It is a health concern associated with physical frailty, an increased risk of complication, and a higher mortality.

Overall, it can reduce the quality of life of those experiencing it, as it leads to weakness, reduced mobility, and a higher risk of injury.^1,2 Understanding the causes and mechanisms behind muscle atrophy can help develop a prevention plan and treatment strategies in collaboration with healthcare professionals. 

Although muscle atrophy can occur due to inevitable causes such as ageing, there are other roots of atrophy which may be preventable. This article will explore the different causes, prevention strategies and interventions.  

Types and causes of muscle atrophy 

Muscle atrophy is a consequence of muscle degradation at a rate higher than protein synthesis. Below are some of the most common causes of atrophy.

Disuse atrophy 

As the name suggests, it is caused by a prolonged period of inactivity, which results in a loss of muscle strength and muscle mass. Not engaging muscles for an extended period can reduce the muscle’s ability to break down protein for growth and quicker protein degeneration accounting for the loss of mass.³

When muscles receive fewer neural signals, the muscle fibres will reduce in number and size as the body adapts and breaks down muscle to conserve energy.⁴ Disuse atrophy is often a result of injuries or illness requiring bed rest, a sedentary lifestyle and reduced physical activity. It can be resolved with regular exercise, and in severe cases, physiotherapy.⁵

Cachexia

It is a metabolic syndrome caused by an underlying chronic illness resulting in atrophy. Cachexia highlights the metabolic impact of chronic illnesses, causing weight loss, reduced muscle mass, fatigue, weakness, and a significant loss of appetite. Some conditions associated with cachexic muscle atrophy are cancer, HIV, rheumatoid arthritis, and chronic obstructive pulmonary disease (COPD).⁶

Chronic illnesses can increase energy expenditure, cause hormonal changes, increase inflammatory cytokines (which cause muscle degradation), reduce mobility and result in a decrease in physical activity, all factors contributing to muscle atrophy. As cachexia is a direct result of other conditions, it is managed through medication addressing the primary cause, alongside exercise and a proper diet.⁷

Sarcopenia 

It is the loss of muscle mass and strength due to ageing. With age, there is a natural decrease in hormones such as human growth hormone (HGH), insulin-like growth factor 1 ( IGF-1), and testosterone which support muscle growth and maintenance.^8,9, Another cause of sarcopenia is the slow degeneration of nerve cells stimulating the muscle fibres, leading to a gradual loss of activity in muscle cells, also known as age-related neurodegeneration.¹¹ Other risk factors associated with sarcopenia include chronic conditions.^{10, 11, 12} 

The combination of neurogenic factors and reduced muscle mass presents sarcopenia as a healthcare risk associated with chronic healthcare conditions and lowered physical activity.¹³ Sarcopenia is a very gradual form of atrophy, which may begin as early as in the fourth decade of life, with up to 50% of muscle mass lost by the eighth decade.^14,15 It can be managed through exercise and nutrition, and community initiatives have been targeting the elderly population by keeping them active with activities such as group walks.¹⁶

Malnutrition-related atrophy

It is caused by the lack of essential nutrients required by the body to maintain mass and function.¹⁷ Proteins are the building blocks of muscle tissue, so when the body needs fuel, it breaks down nutritionally dense tissue such as muscle to maintain functions needed for survival. Deficiencies such as iron, B12, and Vitamin D can impair blood circulation to muscle tissue and inhibit muscle growth.

Neurogenic atrophy

Also known as denervation atrophy, is a direct result of an injury or disease affecting the peripheral nervous system. Common causes include amyotrophic lateral sclerosis (ALS), multiple sclerosis (MS), polio, spinal cord injuries, or other nerve damage caused by injuries, diabetes, toxins, or alcohol.^18,19 Atrophy occurs when the damaged nerves disengage from the muscle tissue and are unable to contract them to perform everyday activities. This results in weakness and loss of function in the muscles. Early diagnosis and intervention are highly important to reduce and prevent progression. Neurogenic atrophy can be treated using ultrasound therapy or electrical stimulation.

Spinal muscular atrophy (SMA) 

It is a genetic condition caused by a defect or lack of the SMN1 gene, a protein-coding gene which is responsible for the survival motor neuron (SMN) protein. This protein is crucial for the maintenance and function of motor neurons in the spinal cord, and a deficiency can result in the degeneration and death of neurons.²⁰ The presentation of SMA symptoms at a young age can be an indication of severity, life expectancy and prognosis, but less severe types may not present until late childhood or even in their 30s. 

Prevention strategies 

Neurogenic atrophy and severe cases of spinal atrophy are sudden occurrences with limited planning for prevention, while the other types of atrophy can be prevented to an extent. Prevention strategies differ depending on the different types of muscle atrophy, but prevention can minimise the effects of ageing and chronic conditions on muscle atrophy. 

Diet and nutrition

A complete high-calorie and high-protein diet provides the essential nutrients to support muscle maintenance and growth.²¹ Proteins are the building blocks of muscles and hormones which regulate the body’s biochemistry functioning. A healthy caloric intake provides the body with energy to perform daily tasks and physiological functions without breaking down muscle tissue for energy, thus preventing muscle atrophy.^{22, 23}

Nutritional supplements and appetite stimulants can also help address underlying causes such as poor appetite, especially in the older population. Other nutritional supplements, such as omega-3 fatty acids, which improve cell signalling between nerves and muscle tissue, and citrulline which improves nutrient delivery to muscles, have been studied as preventative strategies and treatments for atrophy.²⁴

Creatine is a supplement that can enhance muscle recovery after an immobile time, possibly due to injury, and amino acids improve protein synthesis. A proper diet can help address different types of atrophies such as disuse, malnutrition, cachexia and sarcopenia.²⁴

Exercise 

Exercise stimulates muscle growth and aids in the maintenance of muscle size. Strength training aids protein synthesis in the muscles, improving the rate of repair and growth of muscle fibres promoting hypertrophy.^25,26 Cardio and HIIT (high-intensity interval training) exercises increase the transport of oxygen and nutrients to the muscles promoting growth. Cardio also improves circulation to and from the muscle, removing metabolic waste and contributing to fatigue.²⁶

Exercise aids muscle maintenance and growth in many ways, such as the secretion of IGF-1, which aids the transportation of amino acids and glucose between muscle cells. These nutrients can accelerate muscle tissue renewal and prevent the degeneration of already present proteins. HGH is also produced after as little as ten minutes of exercise, this hormone promotes protein synthesis and increases the volume and strength of muscles. Exercise with a nutritious diet can counteract muscle degradation and enhance protein synthesis.^27, 

In the case of neurogenic atrophy, passive movements have been found effective in promoting muscle function, even before the start of physiotherapy. A passive range of motion is prescribed to patients who are not yet able to move on their own after an incident or a stroke and is often carried out within a facility under professional guidance. These passive exercises have been shown to lead to significant improvement of motor function which, in the long term, can prevent atrophy.²⁸ 

Specialised interventions 

To treat muscle atrophy medical professionals will address the adverse effects of the symptoms through medications, physical therapy, nutritional intervention, ultrasound therapy, surgery, and supporting accessories such as braces, walking aids or wheelchairs. Patients may require one or a combination of multiple interventions. 

Summary 

Muscle atrophy is characterised by the loss of muscle mass and strength. It presents significant health concerns, including physical frailty and increased risk of complications. It leads to weakness, reduced mobility, and a higher risk of injury, negatively impacting quality of life. 

Understanding the different causes, such as disuse, cachexia, sarcopenia, malnutrition, and neurogenic factors, enables the development of effective prevention and treatment strategies. 

Combining proper nutrition, particularly high-calorie and high-protein diets, with regular exercise can help maintain muscle mass and function, mitigating the effects of various forms of muscle atrophy. 

Specialised medical interventions may also be necessary depending on the underlying causes. Collaborating with healthcare professionals to create tailored prevention plans is essential for managing and reducing the impact of muscle atrophy.