Pulmonary sarcoidosis and exercise appear to be linked, with symptoms of pulmonary sarcoidosis including fatigue, dyspnea, muscle weakness, and exercise intolerance improving with frequent exercise, but worsening with physical inactivity. 

Eager to find out which exercise types may benefit people with pulmonary sarcoidosis without exacerbating fatigue or dyspnea, and whether HIIT should be avoided at all costs. What causes pulmonary sarcoidosis and is it curable? 

This article will address all these questions and more, so be prepared to ‘muscle up’ and keep reading! 

Note: In this article, people associated as male at birth will be referred to as men and people associated as female at birth will be referred to as women. 

Introduction

Overview of sarcoidosis and pulmonary sarcoidosis 

Sarcoidosis is an autoimmune or inflammatory disease that causes the immune system to ‘overreact’ and form granulomas in multiple organs throughout the body, mainly the lungs.¹ In this case, it is called ‘’pulmonary sarcoidosis’’. The granulomas are characterised as lumps of inflammatory or white blood cells, mainly CD4⁺ T cells, which are important to ‘fight off’ infection. 

Prevalence and incidence of sarcoidosis 

Sarcoidosis is rare, with current studies estimating the prevalence and incidence of sarcoidosis to range from 2.17-519 per 100,000 people per year.²

Causes and risk factors of pulmonary sarcoidosis 

To date, it is unclear what causes pulmonary sarcoidosis.³ However, scientists theorise the following factors to increase the risk of developing pulmonary sarcoidosis:

• Genetics: certain genes have been recently shown to increase the risk of pulmonary sarcoidosis including:
  • TNL2 
  • HLA-B 
  • HLA-DPB1
  • ANXA11 
  • IL23R
  • SH2B3/ATXN2 
  • IL12B 
  • NFKB1/MANBA 
  • FAM177B 
  • RAB23
• Environmental factors: such as exposure to:
  • Wood stoves
  • Soil
  • Silica
  • Building supplies
  • Insecticides
  • Tree pollen
  • Gardening materials
• Age: although pulmonary sarcoidosis can occur at any age, people between the ages of 30-55 years appear to be most affected² 
• Sex: women are more at risk of developing pulmonary sarcoidosis compared to men 
• Ethnicity and race: although all ethnic groups and races are susceptible to pulmonary sarcoidosis, people of African-American descent (35.5-64 per 100,000 vs only 10-14 per 100,000 Caucasians) appear to have the highest risk 
• Infectious agents include:
  • Infectious bacteria e.g. Leptospira species, Mycoplasma species, Chlamydia pneumoniae, Borrelia burgdorferi, Pneumocystis jirovecii, Mycobacterium (M.tb) (appears to be the main infectious agent responsible for pulmonary sarcoidosis), and Propionibacterium species 
• Viruses e.g. herpes virus and retrovirus 

Infection is thought to play a key role in the development of pulmonary sarcoidosis since the granulomas are produced as a way of the body ‘protecting’ itself and thus potentially preventing any foreign or harmful invaders, including bacteria and viruses, from entering the body. 

Symptoms and complications of pulmonary sarcoidosis

The symptoms of pulmonary sarcoidosis vary, with some patients experiencing no symptoms (asymptomatic) whilst others experience symptoms that significantly lower their overall quality of life.^1,2 These symptoms include:

• Fatigue (extreme tiredness): this is the most common symptom of pulmonary sarcoidosis
• Pain
• Dyspnea (shortness of breath)
• Muscle weakness
• Persistent cough
• Exercise intolerance: this is characterised by difficulty or inability to perform physical activity 
• Anxiety 
• Depression 

Role of exercise in pulmonary sarcoidosis management

Overview of lungs and how they work during rest versus exercise 

The lungs help us breathe by taking in oxygen (O₂) from the atmosphere when we inhale (breathe in), and removing carbon dioxide (CO₂) and any waste products out into the atmosphere when we exhale (breathe out).⁴ We need oxygen to produce energy required to ‘fuel’ all metabolic and cellular processes, and thus keep us alive. 

Muscles require more oxygen during exercise compared to at rest. During exercise, the oxygen that goes inside the body is pumped directly to the working muscles by the heart. As a result, breathing accelerates significantly from about 15 times per minute (12 litres of air) during rest, to 40-60 times per minute (100 litres of air) during exercise - about a 3- to 4-fold increase! Circulation (blood movement) also increases to ensure that the oxygen in muscles is constantly being replenished. 

Benefits of exercise for pulmonary health

Exercise improves overall pulmonary health by:⁴

• Strengthening muscles: exercise can help muscles become more ‘efficient’, thus requiring less oxygen to move and excreting less carbon dioxide. This in turn puts less strain on the lungs by decreasing the amount of oxygen needed to breathe in and out 
• Strengthening the heart: to work efficiently and be able to provide muscles with sufficient oxygen, the lungs require a strong heart. Exercise can strengthen the heart by making it more ‘efficient’ at pumping blood to muscles and increasing circulation 

Having an efficient and healthy pair of lungs in turn prevents dyspnea (shortness of breath), which is a common symptom in people with pulmonary sarcoidosis.

Potential risks and considerations

As beneficial as exercise is not just for pulmonary health but overall health, exercise carries potential risks for people with pulmonary sarcoidosis including exacerbating:⁴

• Fatigue 
• Pain
• Dyspnea

However, patients with pulmonary sarcoidosis are still encouraged to exercise. As will be discussed shortly, pulmonary sarcoidosis is associated with muscle weakness, thus making it essential to increase muscular strength and in turn potentially improve symptoms, including fatigue and dyspnea.^1,2 So, rather than avoiding all exercise and making matters worse, patients with pulmonary sarcoidosis are advised to consider the type, intensity, frequency, or duration of the exercise performed. 

Types of exercise suitable for pulmonary sarcoidosis patients

Unfortunately, it is currently not entirely clear which types of exercise and at what intensity or frequency prove the most beneficial and suitable for patients with pulmonary sarcoidosis.² 

However, the general consensus among available current research studies is a combination of strength training (resistance training) and aerobic exercise, mainly in the form of moderate-intensity continuous training, such as a gentle 20-30 minute walk or stationary cycling at 70% or less of the maximum work rate.² Low-intensity and low-impact forms of exercise including yoga and swimming have also been reported to improve pulmonary health in sarcoidosis patients without exacerbating fatigue or pain.⁵ 

Some recent studies even suggest incorporating high-intensity interval training (HIIT) into strength-based exercise programmes for pulmonary sarcoidosis patients.^1,2 Interestingly, despite it being a very strenuous form of aerobic exercise, HIIT has been shown to increase muscular strength and improve, rather than exacerbate, fatigue and dyspnea in patients with pulmonary sarcoidosis. 

The longer the frequency or duration of the strength and aerobic exercise programme, the more patients with pulmonary sarcoidosis are speculated to benefit from its effects. A recent study consisting of 14 patients with interstitial lung diseases, 2 (14.3%) of which had sarcoidosis, showed more improvement in dyspnea, exercise capacity, and quality of life after a 12-week compared to an 8-week exercise programme.⁶ 

Studies investigating the link between pulmonary sarcoidosis and exercise

Some scientists believe muscular strength to be one of the main factors linking pulmonary sarcoidosis with exercise.^1,2 

This is due to some scientific evidence consistently showing patients with pulmonary sarcoidosis:¹ 

• Having less muscular strength compared to healthy controls 
• Being more physically inactive compared to healthy controls 
• Experiencing an improvement in exercise intolerance as well as symptoms including fatigue, dyspnea, and overall quality of life following participation in exercise programmes 

Having less muscular strength and being sedentary increases fatigue and dyspnea, which in turn may cause people to lose even more muscle and become more intolerant to exercise, thus ‘fueling the fire’ and creating an ongoing vicious cycle.¹ Therefore, even though increasing physical activity may seem counterintuitive, especially in patients with pulmonary sarcoidosis who are debilitated by fatigue, it appears to be a logical and sound way of ‘breaking’ the vicious cycle. 

The possibility of muscular strength being a key mechanism underlying the link between pulmonary sarcoidosis and exercise may also explain why women are more likely to develop pulmonary sarcoidosis compared to men. Women typically have less muscle mass compared to men and tend to lose even more muscle mass during menopause¹ (permanent absence of periods due to low estrogen levels), which usually occurs between the ages (30-55) when pulmonary sarcoidosis incidence peaks.

However, despite exercise being shown to increase muscular strength and in turn improve fatigue, dyspnea, exercise intolerance, and overall quality of life, exercise has consistently failed to improve pulmonary function in patients with pulmonary sarcoidosis, thus urging further studies to be conducted in this area.^1,2 

Tips for exercising safely with pulmonary sarcoidosis

To reap the most benefits of exercise and improve, rather than exacerbate fatigue, pain, and/or dyspnea, patients with pulmonary sarcoidosis are advised to adhere to the following tips:⁴

1. Including a warm-up and cool-down before and after every workout, respectively
2. Following a tailored exercise programme, ideally under the supervision of a health professional 
3. Increasing the intensity of exercise gradually, ideally under the supervision of a health professional 
4. Stopping or modifying certain exercises when needed
5. Exercising in areas without any of the environmental risk factors mentioned above including building supplies, and tree pollen etc. 

Summary 

People with pulmonary sarcoidosis, an incurable autoimmune disease that mainly causes inflammatory CD4⁺ T cells to accumulate in the lungs and form granulomas, experience debilitating symptoms that negatively affect their overall quality of life, including fatigue and dyspnea. Therefore, adding exercise to the mix appears to be counterintuitive and risky.

However, current research studies suggest otherwise, with fatigue, dyspnea, muscle weakness, exercise intolerance, and overall quality of life in patients with pulmonary sarcoidosis being demonstrated to improve with frequent exercise, but worsen with physical inactivity. 

Despite this, exercise has consistently failed to improve pulmonary function in people with pulmonary sarcoidosis. Instead, exercise has been shown to improve muscle weakness, exercise intolerance, fatigue, and dyspnea, suggesting a link between 

muscular strength, decreased physical activity, fatigue, dyspnea, and quality of life. This theory is supported by evidence showing:

• People with pulmonary sarcoidosis have less muscular strength compared to healthy controls
• Pulmonary sarcoidosis mainly affects 30-55-year-old women, an age range when menopause typically occurs, which is associated with a significant decline in muscle mass and bone density 

It makes sense how increased muscular strength and muscle mass may help ameliorate pulmonary sarcoidosis; they potentially decrease exercise intolerance and fatigue, thus in turn preventing dyspnea, muscle weakness, and further exacerbation of fatigue. 

Therefore, strength training, ideally in combination with aerobic exercise (e.g. walking, stationary cycling etc.), may offer the most benefits for people with pulmonary sarcoidosis. 

However, further studies are required to determine how intense and frequent the strength and aerobic training sessions should be to prevent people with pulmonary sarcoidosis from experiencing any associated adverse events.