Science / Exercise Intolerance: Causes and Symptoms

Exercise Intolerance: Causes, Symptoms and Respiratory Muscle Training

by Patrick McKeown

Exercise causes pain and soreness. As we push ourselves to improve, we can experience exhaustion after working out. While it often hurts, exercise is incredibly beneficial to our health. For some people however, the high levels of pain and exhaustion after working out may be the very thing preventing them from doing anything at all.

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The joints and muscles are stretched and moved during exercise. Various types of exercise can stress the muscles and joints leaving us sore and tired but this is a natural and necessary pain. These levels of pain and stress can increase as we age and / or face health challenges.

When the individual is breathing too hard and too fast during exercise, their breathing is holding them back. When a young and healthy adult suffers disproportionate breathlessness and can’t withstand the normal stress of physical exercise, they may be suffering from exercise intolerance.

Join us as we look at the causes, symptoms and remedies for this and related conditions.

What is Exercise Intolerance?

Exercise intolerance is a condition in which the individual has an inability to perform physical exercises or a decreased ability. These are exercises that should be possible for the individual, considering their age, sex, size and muscle mass.

Possible Causes of Exercise Intolerance

A lot of factors can contribute to exercise intolerance, here are a few examples:

Heart diseases

Exercise is good for people with coronary issues. It reduces the level of cholesterol in the blood vessels and helps in blood circulation. But our ability to perform exercise is powered by our heart. Our heart is the muscle that drives blood through the body, but the heart needs its own supply of blood and oxygen. How we breathe influences blood flow and oxygen delivery to the heart.

Cardiovascular disease obstructs the efficiency of blood flow to the muscles. Individuals suffering from any cardiovascular disease, have a reduced ability to perform physical exercises.

Lung issues

Similar to the heart, the lungs play an important role in exercise. It is with the lungs that oxygen is supplied to the blood which travels to the heart and is pumped through the rest of the body. If gas exchange from the lungs to the blood is poor, the individual will experience strong breathlessness during physical exercise and a lowering of their blood oxygen saturation.

Tears in the muscles

The muscles bear the stress of exercise. If muscle fibers rupture, you will find it very difficult to carry out physical exercise. Muscles are part of a coordinated bodily system. Any defect in the fibers causes pain to the body, making exercise extremely difficult.

Bruises, wounds or injuries

In a similar vein to muscle tears, any form of cut or injury to the body could lead to exercise intolerance. Regular, exercise-induced pain is already challenging enough. Adding the pain from bruises, wounds or injuries on the body can be intolerable.

Symptoms of Exercise Intolerance

What to look out for.

Exercise intolerance symptoms can present themselves in a number of ways. While each symptom alone does not mean you suffer from the condition; a combination of symptoms likely means it is something you need to investigate further.

If you notice a number of the following symptoms while exercising, you are likely susceptible to exercise intolerance.

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Unusual and severe fatigue

It is normal to get tired after exercise. But severe fatigue after working out is a possible symptom of exercise intolerance. You can easily spot the change. Compare how tired you used to get after exercise and how exhausted you get presently. You can also judge by comparing the duration of the exercises, before and now. Are you suffering more exercise fatigue symptoms than usual after a workout? Even though that exercise lasted the same duration as before. This is a red flag.

Uncontrolled breathing

Your tolerance to carbon dioxide influences how hard and fast you breathe during physical exercise. If you have a strong sensitivity to the accumulation of carbon dioxide in the blood, you will experience disproportionate breathlessness.

In addition, because of the harder and faster breathing, your breathing muscles consume more oxygen, leaving less oxygen for muscle movement. Athletes in the main, have a reduced sensitivity to the accumulation of carbon dioxide.

Your comfortable breath hold time (BOLT) as measured during wakefulness, provides feedback of your sensitivity to carbon dioxide. If you have a low BOLT score, it implies that you have a strong sensitivity to carbon dioxide in the blood. This results in harder and faster breathing and more upper chest breathing. OA exercises are specifically designed to reduce the body’s chemosensitivity to carbon dioxide, resulting in improved exercise tolerance.

Pain in the chest region

If you notice unusual chest pain while you exercise, it may be a risk factor for exercise intolerance. This pain can also spread to the neck, arms and generally, the joints. With any chest pain however, the first thing to do is get the all clear from your doctor. Chest pain can be caused by breathing pattern disorders possibly due to overuse of the upper chest breathing muscles.

Prolonged muscular cramps

Muscular cramps are a common occurrence while exercising. They can occur for a variety of reasons. Muscular cramps during or after exercise usually last for a few minutes. However, when muscular cramps last for a prolonged period of time, it can cause exercise intolerance.

Unusual sweating

It is normal to sweat during exercise, in fact, it is healthy. But with exercise intolerance, just a little exercise and you can be soaked in sweat. Exercise intolerance sufferers tend to sweat profusely over little things that ordinarily wouldn’t cause you to break a sweat.

How to Prevent and Aid Exercise Intolerance

Reduce symptoms and improve wellbeing.

Early diagnosis of exercise intolerance will result in better management. So how does one continue to engage in exercise while preventing the onset of exercise intolerance symptoms? If you are diagnosed with exercise intolerance, you should adopt the following workouts for exercise intolerance to help manage the condition:

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Practice slow breathing exercises

Nose and slow breathing helps improve gas exchange from the lung to the blood and from the blood to the working muscles. It is through this oxidative process that the energy we need for physical activities is released. Functional breathing should be practiced during exercise to incorporate good breathing techniques and improved efficiency. This way, you won’t get worn out easily when you exercise with faster recovery post exercise.

Breathe slow

Cut down on your exercise routine and take it a bit slower

You may consider dropping some of your exercise routines in order to maintain your muscular strength capacity. All recreational athletes should breathe through the nose during exercise. Allow the nose to determine the intensity of your physical exercise.

If the need for air is too strong that you need to switch to mouth breathing, slow down the intensity of movement. As you continue physical exercise with your mouth closed, the air hunger diminishes. Normally it takes about 6-8 weeks with the mouth closed to experience a decrease in air hunger. This signifies increased tolerance to carbon dioxide.

Easing off mental stress

Sometimes, exercise intolerance can occur as a result of your mental health. If you are mentally stressed, you will tire easily during exercise. The mind and the body are in synergy and as such, a stressed brain IS a stressed body. Use functional breathing to relax your mind before and after your exercises.

Respiratory Muscle Training and Diaphragm Fatigue

Reduce Breathlessness and Support Your Core

Have you ever tailed off at the end of a race because you can’t breathe? Then you already understand how strong breathing muscles may improve exercise performance. Particularly in endurance events.

Respiratory muscle training is a great technique for any athlete wishing to improve their respiratory muscle strength or to treat conditions such as diaphragm fatigue. Let’s find out how it works. And how you can integrate it into your workout.

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What is Respiratory Muscle Training?

Respiratory muscle training involves strengthening the breathing muscles. It improves inspiratory and expiratory muscle strength.

The technique creates functional and structural changes in the body. It builds endurance and boosts exercise performance.

What is the Main Respiratory Muscle?

The diaphragm is the biggest breathing muscle. It’s a dome-shaped sheet of muscle that sits below the ribs. During inhalation, it contracts and flattens. During exhalation it returns to its original shape. Efficient healthy breathing is from the diaphragm.

A healthy diaphragm is vital for core strength. As it descends during inhalation, pressure is produced in the abdomen. This “intra-abdominal pressure” stabilizes the spine and pelvis, supporting functional movement.

The diaphragm is the same type of muscle as the skeletal muscles. It’s possible to improve diaphragm muscle function. But it’s also a muscle, so subject to fatigue.

Breath in Breath out

The Role of the Diaphragm During Exercise

During physical activity, the diaphragm contracts to pump oxygen-rich blood from the lungs to the working muscles. The steady supply of oxygen to the muscles ensures they are equipped with sufficient energy to carry out their functions.

What are the Symptoms of a Weak Diaphragm?

When you exercise, breathing volume increases and the breathing muscles have to pump a lot more air. They can become exhausted, leaving you breathless. Blood circulation diverts from the legs to support the diaphragm, forcing you to slow down and stop.

Poor respiratory muscle function produces symptoms including:

  • Breathlessness on exertion.
  • Diaphragm muscle pain that interferes with breathing.
  • Lower back pain and injury.
  • Poor balance.
  • Poor core muscle strength.
  • Pelvic floor problems.
  • Reduced blood flow to the legs.

How Do I Make My Breathing Stronger?

To strengthen the breathing, we first begin to pay attention to it. Awareness is the first step towards better breathing.

Every athlete knows that when you want to strengthen a muscle, you need to use it more. But how do you build tone in the diaphragm?

  1. Respiratory muscle training in its simplest form, involves adding a load to breathing. This means extra resistance. You can begin strengthening your diaphragm by breathing only through your nose. The nose adds resistance to airflow. Nasal breathing naturally engages the diaphragm.
  2. Another way that doesn’t involve gadgets or mouth breathing is the Oxygen Advantage®. This program of functional breathing exercises can simulate high altitude training and help improve performance.
  3. Oxygen Advantage’s SportMask pools carbon dioxide to improve breathing from a biochemical dimension and reduce breathlessness during physical exercise. By adjusting the valve on the mask, airflow can be restricted during rest or physical exercise.

This adds an extra load onto the breathing muscles to help strengthen them. Wearing SportsMask, the user can breathe in and out through the nose, enabling better recruitment of the diaphragm.

How Do Breathing Exercises Work?

The exercises involve holding your breath after a passive exhalation. You do this until you feel a strong ‘air hunger’. Carbon dioxide accumulates in the blood while the muscles continue to extract oxygen. The result – hypoxia and hypercapnia (low blood oxygen/high CO2). This will help reduce the body’s sensitivity to CO2 and help improve your endurance.

Breath holding also produces discomfort in the diaphragm. The brain begins signaling to the diaphragm to resume breathing. It wants to get blood gas levels back to normal. As the breath hold continues, your diaphragm repeatedly contracts. As contractions increase, your diaphragm gets an intensive workout.

Diaphragm strengthening exercises produce functional adaptations. This means greater strength, speed, power and endurance, and better peak inspiratory flow (lung capacity). The exercises also trigger structural changes in muscle fiber type and thickness.

What to Expect

  • Less breathing effort
  • Reduced respiratory muscle fatigue
  • Healthy breathing pattern
  • Delayed lactic acid and fatigue
  • Improved oxygen uptake
  • Less whole-body effort

Inspiratory muscle training is a powerful way to improve aerobic exercise. It’s ideal for running or cycling where endurance is important. No longer hampered by breathlessness, you’re free to keep going till the finish line.

N.B. These exercises are designed for athletes who want to enhance performance. If you have a respiratory condition, please consult a medical doctor before practicing strong breath holds. If possible, learn the exercises with a certified Oxygen Advantage® instructor.

Effects of Diaphragm Fatigue on Exercise Tolerance

One limiting factor in the ability to exercise, is diaphragm fatigue. If taken lightly and left untreated, diaphragm fatigue will negatively affect exercise tolerance.

What Is Diaphragm Fatigue?

Diaphragm fatigue is a condition often caused by an overworked diaphragm. The diaphragm is the main muscle for breathing. However, when the diaphragm is overworked, it becomes tired. This can compromise its function.

How Does Diaphragm Fatigue Affect Exercise Tolerance?

When the diaphragm fatigues, it can no longer contract forcefully, reducing the amount of oxygen that can enter the lungs. This can lead to a decrease in exercise tolerance and cause shortness of breath during physical activity.

What Causes Diaphragm Fatigue?

There are many possible causes of diaphragm fatigue, and there are several mechanisms by which diaphragm fatigue can occur.

  1. The diaphragm can be stretched beyond its normal range of motion during heavy or prolonged breathing.
  2. The diaphragm can become exhausted from repeated contraction and relaxation during exercise. This can lead to a painful build-up of lactic acid in the muscle.
  3. The blood supply to the diaphragm can be reduced during exercise.

It can be difficult to pinpoint the exact cause of diaphragm fatigue in any given individual. However, possible causes include:

  • Excessive use of the diaphragm during exercise or other strenuous activity.
  • Damage to the diaphragm due to injury or surgery.
  • Nerve damage or dysfunction affecting the diaphragm.
  • Weakness of the diaphragm muscles.
  • Dehydration.
  • Respiratory infections.

It is important to stay well-hydrated and replenish electrolytes during strenuous exercise to prevent diaphragm fatigue. In cases of fatigue or shortness of breath during any physical exercise, it is necessary to stop and rest until the symptoms subside.

How Can Diaphragm Fatigue Be Treated?

You can treat diaphragm fatigue through various methods, including:

  • Resting the diaphragm
  • Deep breathing exercises
  • Electrical stimulation
  • Surgery

However, the most effective treatment is typically rest. This means that the individual will need to take a break from any activity that causes the diaphragm to fatigue.

How Can Diaphragm Fatigue Be Prevented?

There are several ways that athletes can prevent diaphragm fatigue.

  • First and foremost, it’s important to maintain good posture to ensure that the core muscles are strong. This will help to keep the spine in alignment and minimize the diaphragm’s work.
  • To prevent diaphragm fatigue, stretching and breathing with good recruitment of the diaphragm can prove very effective. This will improve the flexibility and strength of your respiratory muscles, allowing them to work more efficiently.
  • Finally, it is always helpful to keep the body well-hydrated. Drinking plenty of water before, during, and after a workout prevents dehydration and muscle fatigue.

The diaphragm is a muscle that plays a critical role in respiration. When it becomes fatigued, it can cause a decline in exercise tolerance. This means that the body can no longer produce the same energy or work as before, leading to decreased performance.

If your fatigue persists despite these measures, it is important to see a doctor so they can rule out any other potential causes. Once other causes have been ruled out, your doctor can help you develop a plan to manage your diaphragm fatigue.

Improving Respiratory Muscle Strength: The Science

As we have already established, respiratory muscles such as the diaphragm, are just that, muscles. As such, they are susceptible to fatigue and weakness just like any other muscle. When this happens it can negatively affect our ability to function at the highest standard. For example, when the diaphragm fatigues, it reduces the amount of oxygen entering the lungs because it can no longer contract forcefully enough to bring sufficient air into the lungs.

Read on to learn the science behind why our respiratory muscles might tire and what we can do to improve our respiratory muscle strength.

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Respiratory system limitations can impact exercise performance in highly trained individuals (Boutellier et al. 1992), especially at high intensities, where the increased work of breathing results in compromised exercise performance (Harms et al. 2000).

Furthermore, respiratory muscle fatigue not only decreases the ability to ventilate adequately (Lomax and McConnell 2003), but also increases limb muscle sympathetic nerve activity (MSNA) (St Croix et al. 2000), which has been shown to reduce blood flow to the peripheral muscles (Sheel et al. 2001). The dyspnea (shortness of breath) experienced may limit an individual’s ability to continue to exercise at the required intensity (Altose et al. 1985). Eur J Appl Physiol (2005) 94: 527–540

Restricting air intake during physical exercise provides the respiratory muscles with an extra load, which in turn works the breathing muscles more intensely to strengthen them.

Effects of Hypercapnic-Hypoxic Training on Respiratory Muscle Strength

A study was carried out to determine the effects of an 8-week hypercapnic-hypoxic (H-H or breath holding) training program on respiratory muscle strength and 100-meter crawl swimming performance. The study was conducted on a sample of 26 elite Croatian swimmers (experimental group [EG] n=12, control group [CG] n=14).

Both groups were subjected to the same swimming training programs and training sessions on a treadmill. The experimental group was additionally subjected to hypercapnic-hypoxic training program with increased muscular activity.

The group of swimmers, who were subjected to the hypercapnic-hypoxic regimen, had significantly improved strength of their inspiratory and expiratory muscles in comparison to swimmers in the control group. The swimmers from the experimental group had improved the inspiratory muscle strength values (MIP) by 14.9% and the expiratory muscle strength values (MEP) by 1.9% in relation to the control group.

Based on the results of this study it can be assumed that the hypercapnic-hypoxic practice has significantly increased the respiratory muscle strength. Statistically significant differences can be attributed to the eight-week exposure to hypercapnia and hypoxia combined with increased muscle activity. Such practice may have enlarged the diaphragm thickness which plays an important role in respiratory system and sports performance.

Voluntary holding of breath may result in involuntary contractions of the diaphragm during the hypercapnic-hypoxic practice. It is also assumed that above mentioned contraction occurrence has resulted in hypertrophy of intercostal muscles. According to the available literature, mobility of breastbone and costal joints and changes in lung and breast muscle elasticity are also possible changes that occur during voluntary breath holding.

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