In the Age of Coronavirus, education is our best chance of maintaining the health and safety of our communities. We know about hand hygiene, social distancing and appropriate use of masks. We know of the innumerable benefits of exercise: it improves cardiovascular health, decreases depression, relieves anxiety symptoms and helps in weight management.
However, various types and duration of exercise may in fact cause more harm to the immune system than good. In the world as we currently know it, optimizing health and immunity has become a priority.
Not all exercise is equal when we consider the effect on the immune system. For cardiovascular health, the American Heart Association (AHA) recommends 150 minutes of moderate activity or 75 minutes of intense activity for adults each week. For children older than 6, the recommendation is 60 minutes of physical activity daily. Muscle-strengthening exercise is recommended twice weekly for adults and three times per week for children over 6 years old.
Nonetheless, it has been well-established that too much exercise may in fact transform a robust immune system to one that may be more prone to infection.
But why is it that some elite athletes are more prone to infection than, say, the average Joe? It all boils down to the body’s response to physical activity.
How the Body Responds to Exercise
Antibodies (also called immunoglobulins) and white blood cells (WBCs) compose a significant amount of the body’s home defense. They protect the body against foreign invaders such as bacteria and viruses. With mild to moderate physical activity, the immune system experiences a boost in circulating WBCs, particularly neutrophils and lymphocytes, and an increase in immunoglobulins. With significant, high-intensity exercise, and over a prolonged period of time, immunoglobulins and WBCs can actually decrease. There can also be an increase in certain hormones such as adrenaline and cortisol, which suppress the immune system by a different pathway. This may explain why studies have observed elite athletes with an increased rate of upper respiratory tract infections (URIs) in the days to weeks following a surge of exercise. This particularly applies to endurance athletes who average greater than 90 minutes of intense physical activity daily.
In Sports Medicine, we utilize a concept we lovingly call the “neck check,” which is applied to any ill athlete prior to permitting participation in practice or competition. To summarize this principle, any athlete with symptoms above the neck (commonly nasal congestion, ear aches, sore throat) may still be permitted to participate in exercise. Meanwhile, those with symptoms below the neck (systemic symptoms such as fever, body aches, diarrhea and vomiting) are generally held from activity until symptoms resolve.
Why Keep Someone From Exercising?
The rationale behind holding someone from physical activity who doesn’t pass the “neck check” is the concern for transmitting disease. There’s also the potential for poor tissue oxygenation, subsequent dehydration and physiologic damage to organs that may occur by certain infectious pathogens.
People who exercise when they are systemically ill also often start without being properly hydrated. Having a fever more quickly burns off an individual’s fluid reserve, thus predisposing one to complications of dehydration. This effect can be compounded in individuals who not only have fevers but are also experiencing gastrointestinal issues such as diarrhea and vomiting. That can lead to quicker rates of dehydration.
A lack of muscle oxygenation can lead to poor performance and cell breakdown. Certain infectious pathogens have been shown to predispose individuals to the development of cardiac conditions such as pericarditis or dilated cardiomyopathy (DCM), in addition to causing inflammation of other organs such as the liver and spleen.
How to Exercise Safely
Precautions to take while exercising include:
- Maintain safe distances
- Practice adequate hand and exercise surface hygiene
- Be mindful of the “neck check” guideline
- Breathe through the nose as opposed to through the mouth. This allows for more of the body’s natural defenses to filter potential pathogens from the air.
Most importantly ― keep moving and fueling those good, protective immunity-boosting cells!