Ultrarunning: The Immune System of Ultrarunners

October 10, 2011

This article is part of Endurance Planet’s ultrarunning article series. If you have questions, comments or feedback about “The Immune System of Ultrarunners”, please leave it below in the comments section…

It has been studied and proven that an average person can boost his immune system with adequate amounts of moderate exercise. So why is it that endurance athletes like ultrarunners, supposedly far healthier than the average health buff, seem to be more susceptible to ailments such as the flu?

You may have heard about this or experienced it yourself. After a particularly demanding long run or an ultramarathon event, the recovery period is usually accompanied with some sniffles, coughing, and maybe even light fever. To help you understand and cope with this occurrence, the following is a brief discussion about this peculiar characteristic of an ultrarunner’s immune system.

Greater demand

The ultrarunner is apparently not your average runner and his training cannot be described as ‘moderate exercise’. Like those who train and participate in endurance taxing sports such as distance cycling, marathons, and triathlons, ultramarathoners push their bodies at or near the limits with the aim of increasing both the physical and mental thresholds in order to succeed in the event. This greater demand puts a short gap of vulnerability on the immune system.

In general terms here’s what happens to your body when you undergo ultramarathon training. As the time or distance of your running sessions increase, your body burns more fat and carbohydrates. Eventually these fuel sources start getting low. At that point your body shifts and also begins using up amino acids which are the basic components of protein.

Now the immune system needs protein in order to function properly. Since long running sessions lowers the level of amino acids, there is a brief window, between the workout and until your body reproduces protein to adequate levels, where you immune system is at a somewhat less than optimal state. Hence there is a more common occurrence of illness during the recovery periods.

Colds, flu, and other similar ailments typically happen after your longest training run, the one that leads into the tapering period, and also after the ultramarathon event itself. It is at these two times where you demanded the most of your body’s capacity.

Greater supply

Since you’re pushing your thresholds to their maximum, it naturally follows that you should supply yourself with more nutrition. Protein and glutamine (a type of amino acid) are the main concerns because of their direct influence on the immune system. Protein helps maintain aerobic metabolism and supports tissue repair. Meanwhile glutamine increases the number of lymphocytes and macrophages which are types of cells that carry out the immune system’s functions.

How much more you need to take usually depends on you body weight and possibly other pre-existing conditions. In any case the dosage is most likely going to be significantly more than the recommended daily allowance for regular adults. Some runners simply become more conscious about including more of these elements in their diet while others also make use of supplements. Hopefully by boosting your nutrition to meet the greater demands you’re making of your body, you’ll experience smoother and more illness-free recovery periods.


Do you have questions about the particular nature of ultrarunners’ immune systems, or what you’ve read so far? Do you have any ultrarunning pointers of your own to add? Please leave your feedback, comments and questions below, and we promise we’ll respond.

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