Exercise intolerance refers to a decreased ability to engage in physical activity usually possible for a person’s age and size. It is a symptom of many medical conditions, particularly those that cause problems with the heart, muscle contractions, or energy levels.
Exercise intolerance is different from having less strength or stamina than others — it is not the result of a lack of motivation. In some cases, it can be debilitating and prevent someone from carrying out everyday tasks.
In this article, we look at what exercise intolerance is, as well as its symptoms, causes, associated conditions, and how people can manage it.
Exercise intolerance is a reduced ability to exercise at a level that is typical for someone’s age and size. Individuals with exercise intolerance may not be able to exercise as vigorously as they used to, or they may get tired or out of breath very quickly after they start exercising.
The extent that exercise intolerance affects people can vary dramatically. Some could participate in some forms of exercise but then have to stop earlier than they did previously. Others might not participate in much physical activity at all due to their symptoms.
Exercise intolerance is not the same as someone having a low level of physical fitness.
In most cases, people who have not exercised in a while can benefit from physical activity and slowly build their strength. The more accustomed to handling exercise they become, the more they can do comfortably.
In contrast, those with exercise intolerance struggle to build this tolerance. And depending on the cause, physical activity may make their symptoms significantly worse.
The main sign of exercise intolerance is a consistent inability to engage in a reasonable level of physical activity. This may make someone feel:
- out of breath
- in pain
Depending on the cause, a person may also experience muscle cramps, dizziness, or postexertional malaise (PEM).
Exercise intolerance and PEM
PEM is similar to exercise intolerance in that it can prevent someone from exercising or being physically active. However, where exercise intolerance makes it difficult to begin or continue exercising in the present, PEM causes a delayed reaction.
With PEM, a person’s preexisting medical symptoms get worse around
Individuals can experience exercise intolerance because they have underlying conditions that interfere with blood circulation, breathing, metabolism, or energy. Many conditions can cause these problems. Some examples include the below.
Respiratory conditions, such as asthma, chronic obstructive pulmonary disease, and lung cancer, can make it more difficult to get enough oxygen due to a reduced ability to breathe. This may cause exercise intolerance in varying degrees, depending on how the severity of symptoms.
People with respiratory conditions may feel short of breath, lightheaded, or dizzy when they exercise. Strenuous activity may also trigger coughing or asthma symptoms, such as wheezing or tightness in the chest.
Post-viral syndrome and long COVID
Sometimes, people experience persistent fatigue and weakness for weeks or months following a viral illness. Health experts refer to this as post-viral fatigue or post-viral syndrome.
Since the COVID-19 pandemic, many individuals have developed a post-viral syndrome following a SARS-CoV-2 infection, which many know as long COVID. Both post-viral syndrome and long COVID can cause exercise intolerance.
Scientists are not sure why post-viral syndrome or long COVID develop, but they may result from the immune system becoming overactive, even after the infection passes. This may also explain why people may experience a lingering sore throat, swollen lymph nodes, and body aches.
Myalgic encephalitis or chronic fatigue syndrome
Myalgic encephalitis, or chronic fatigue syndrome (ME/CFS), causes a persistent lack of energy that does not get better with rest or sleep. For a diagnosis of this condition, symptoms must last for more than
Scientists are not sure why ME/CFS develops, but
Exercise intolerance and PEM are hallmark symptoms of ME/CFS.
Diabetes affects how the body reacts to and uses glucose, which gives cells the energy they need to work. A 2015 study states exercise intolerance can occur in people with type 2 diabetes independently of other factors that may hinder exercise, such as cardiovascular disease.
Diabetes-related exercise intolerance occurs due to blood vessels not working as they should, reducing a person’s circulation. This makes it challenging for individuals with type 2 diabetes to exercise, which can be difficult, as it is often part of diabetes management.
People with metabolic myopathies have genetic conditions that impact how their body uses energy. For individuals with these conditions, too much physical activity can cause muscles to break down in a process doctors call rhabdomyolysis, which is painful and can damage the kidneys.
There are many types of metabolic myopathy, but many cause similar symptoms, such as:
- exercise intolerance
- painful muscle cramps
- heart problems
- rust-colored urine
Motor neuron disease
Motor neuron diseases are a group of conditions that occur when the brain and nerves cannot communicate with muscles, causing problems with movement. Over time, this leads to weaker muscles, an inability to move, and increased fatigue levels.
There is debate among scientists as to whether any amount of exercise is harmful or beneficial to people with different types of motor neuron disease, according to a 2020 editorial.
Any heart condition that impairs its ability to pump blood may cause increased difficulty exercising, but exercise intolerance, more specifically, is a key symptom of chronic heart failure. Heart failure occurs when it can no longer pump blood around the body as it should.
According to a 2019 review, exercise intolerance in people with heart failure has links with worse outcomes and a higher risk of cardiac arrest. However, if doctors can identify the mechanisms behind it, they could improve someone’s capacity for exercise.
How people manage exercise intolerance depends very much on the underlying cause. For some, any amount of physical activity may be harmful or even dangerous. For others, exercising within certain limits may be beneficial.
The first step in managing persistent fatigue or inability to exercise is to speak with a doctor. It is important to find the cause for exercise intolerance and rule out serious conditions.
A person can help this process by:
- Finding a knowledgeable doctor: According to the
Centers for Disease Control and Prevention (CDC), most medical schools in the United States do not teach doctors about ME/CFS. This can make it difficult for people with energy-limiting conditions to get a diagnosis or support. If necessary, seek second or third opinions or ask someone to attend appointments as an advocate.
- Learning individual limits: It is helpful to identify how much exercise or activity an individual can tolerate without causing worsened symptoms. Try keeping a diary to track the type and intensity of activity a person participates in and any symptoms that occur. Remember that even everyday tasks, such as housework, could be physically demanding.
- Reducing energy output: People with exercise intolerance may benefit from adapting how they move to reduce exertion. This could include sitting down to prepare food or fold laundry, or using assistive equipment, such as a stool they can sit on in the shower. An occupational therapist could assist with making adaptations.
- Pacing: Pacing is a technique involving planning tasks ahead of time so that they do not become too strenuous. For example, people can space apart activities that demand a lot of energy and block off time before and after for rest and recovery.
- Listening to the body: Take cues from symptoms and how the body feels rather than trying to stick to a specific exercise goal or to-do list. Only increase physical activity if it feels safe to do so and do not try to push through fatigue or pain.
- Asking for help: Sometimes, tasks are too much for people with exercise intolerance. When possible, try not to struggle through them alone. Friends, family, or neighbors could help with simple errands, such as carrying heavy groceries.
If severe symptoms occur during or after exercise or activity, a person may need to call 911 or the number of the nearest emergency department. Seek immediate medical attention for any of the following symptoms:
- chest pain, squeezing, or pressure
- pain in the arms, neck, or jaw
- difficulty breathing
- blue or white lips
- feeling faint
- loss of consciousness
Exercise intolerance is a symptom of many medical conditions. It occurs when the body is unable to cope with physical activity due to an impairment in breathing, blood circulation, muscle movement, or energy levels.
Talk with a doctor if any unexplained symptoms occur during or after exercise or other physical activities.