August 11, 2021 3 min read

 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. 

  1. First and foremost, nutrition. A well-balanced diet can help to combat the negative inflammatory effects of activity. This can come in the form of traditional food products, and also in the form of supplementation like the PNG Immunity Boost and Whey Protein, or a combination of both to address any holes in your dietary needs
  2. Through a consistent and restful pattern of sleep and recovery. Though exercise has been shown in increase immune function overall, too much of a good thing can be bad. Your body needs time to recover, and to process and heal from the damage it incurs through training and competition. Again, products like Whey Protein have been shown to facilitate more rapid recovery. 
  3. Being mindful of your body’s needs and impulses. Listen to what your body is telling you. If you’re on the brink of illness or injury, it will tell you. Be receptive to these impulses and listen. Back off the intensity and volume a bit, and let your body take the time it needs to heal and recover. 


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 exercise34(8), 1242–1248.

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