The immune system is known for its ability to fight off deadly pathogens, protecting us from infection, and keeping us healthy and ready to battle it out in our sport of choice. In early research there was a long-standing theory that prolonged vigorous exercise led to a suppression of the immune system, leaving the athlete more susceptible to infection or illness. And while there is some research to substantiate this claim, it has become clear that prolonged, or habituated exercise does more to boost your immune function than to inhibit it.
In an article published by Matthews et al. (2002) looking at the link betweenmoderate to vigorous physical activity and risk of upper-respiratory tract infection on endurance athletes, it was found that athletes who performed ~2 hours of moderate intensity exercise per week saw a 29% reduction in risk of developing upper respiratory tract infection compared to those living a more sedentary lifestyle. This same study, however, also indicated that those who have recently completed an ultra-endurance event saw a 100%-500% increased risk for developing upper respiratory tract infection in the following weeks. So, it’s been postulated that while maintaining an active lifestyle is important to increased immune function, there may be a tipping point where activity begins to cause a decrease in immune function.
Figure 1 Gleeson, M. (2007). Journal of Applied Physiology: Immune Function in Sport and Exercise
There are a handful of theories as to why endurance athletes might be more susceptible to infection. Foremost on the list is that moderate to vigorous exercise causes an increase in stress hormone production and circulation, which in turn drives down circulating leukocyte and glutamine levels- two substances that have been found to be crucial to immune function and health. Another plausible factor is that endurance athletes have a higher exposure level to airborne pathogens due to prolonged increase breath volume, and breathing rate. Essentially, we spend a great deal of time breathing in large volumes of air and an increased rate when compared to the general population. It’s easy to see how this might equate to more particulates entering our body.
While the research seems to indicate a relatively even split on the subject one thing is for certain. If we have the means to strengthen our immune system, why shouldn’t we? We know that increased exercise drives up the production of stress hormones, increases inflammation, and decreases leukocyte levels in the body, leaving us open and more prone to infection. In my experience I’ve observed three key methods to maintain a healthy level of activity and a balanced immune system.
Endurance Training and Immune Health
Kyle McFarland- White Pine Athletics
Gleeson, M. (2007). Journal of Applied Physiology: Immune Function in Sport and Exercise
Matthews, C. E., Ockene, I. S., Freedson, P. S., Rosal, M. C., Merriam, P. A., & Hebert, J. R. (2002). Moderate to vigorous physical activity and risk of upper-respiratory tract infection. Medicine and science in sports and exercise, 34(8), 1242–1248. https://doi.org/10.1097/00005768-200208000-00003
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