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  • Writer's pictureArianne Gosselin

Exercise and Immunity

If you fear getting the flu or even the common cold, you’re probably constantly trying to find ways to boost your immune system. If this sounds like you, then you may already know that exercise is one of the best ways to do this, but do you know why? Let’s explore what happens to one particular organ when you exercise: the spleen.

The spleen is an important organ for your immunity because it contains immune cells (such as lymphocytes and monocytes) that destroy harmful bacteria and pathogens in your body. Your spleen accomplishes its immune functions by filtering your blood and removing the harmful things it encounters.

Now let’s compare the spleen to a common everyday item that most people have in their kitchen: a sink strainer. What would happen if the strainer got clogged? Water wouldn’t be able to pass through anymore (or very little) and debris would accumulate, causing even more blockage. Things that get stuck may then begin to rot and ferment, leading to an unfortunate smell…

What if this strainer was your spleen and the liquid being poured down the sink was your blood? A blockage in your spleen or a spleen that does not contract appropriately would lead to a pooling of blood and an accumulation of bacteria and pathogens (among many other things). This would cause the spleen to swell, a condition called splenomegaly. The immune cells are now outnumbered by the things they must destroy, and the spleen cannot function efficiently anymore. This spleen needs help, and you are the best person to help it. But how? Physical activity of course!

A very recent study demonstrated the effects of treadmill exercise on the volume of the spleen (Jahic et al., 2019). While we already know that the spleen contracts during physical activity, the authors gave some interesting numbers. Based on their review of the literature, they found that “the human spleen shows a decrease in volume, in range from 8% to 56%, depending on the work intensity” (Jahic et al., 2019). This means that exercise allows your spleen to be more efficient, creating space to filter more blood and therefore get rid of more of the bad stuff that could harm your health. They also noted that elite long-distance runners had a greater decrease in their spleen volume than recreational runners (Jahic et al, 2019). This means that the effect is even better the fitter you are.

This concept is not new to us. In 1993, Nieman et al. demonstrated that elderly women (67-85 years of age) who were very active were better able to fight off infection because their immune cells showed greater activity than sedentary women of the same age group. (Nieman D.C. et al, 1993). Numerous other studies have come to the same conclusion. Essentially: the fitter you are, the better your immune system. This sounds like a great reason to get active!


Jahic D. et al “Changes in Splenic Volume After the Treadmill Exercise at Specific Workloads in Elite Long-Distance Runners and Recreational Runners.” Med Arch 73, no. 1 (2019): 32-34. doi 10.5455/medarh.2019.73.32-34

Nieman DC et al “Physical activity and immune function in elderly women.” Medicine & Science in Sports & Exercise 25, no. 7 (1993): 823-31

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