Immune System Takes A Beating

So with time off to rest with the cold, I've had some time to research why I got sick in the first place. My mom has already made remarks that she's ditching her exercise program if it causes her to get sick. Not so fast mom. At first glance she's correct. I exercise five to six days a week and eat a healthy diet, so why shouldn't I be Superman to the lowly nemesis, the germ?

In both cases where I got sick this year I was either ramping up the mileage or increasing the amount of activity in my exercise schedule, thus causing stress to my immune system.

About.comThe effect of exercise on immune system function is generally positive. For moderate exercisers the immune systems gets a temporary boost in the production of macrophages, the cells that attack bacteria. Regular, consistent exercise can lead to substantial benefits in immune sytem health over the long-term.

However, intense exercise seems to cause a temporary decrease in immune system finction. Reserach has found that during intense physical exertion, the body produces certain hormones that temporarily lower immunity. Cortisol and adrenaline, known as the stress hormones, raise blood pressure and cholesterol levels and suppress the immune system. This effect has been linked to the increased susceptibility to infection in endurance athletes after extreme exercise (such as marathon running or ironman distance triathlon training).

Here's a graph that explains simply what happens. It's from Research Digest, President's Council on Physical Fitness and Sports, June 2001. Does Exercise Alter Immune Function and Respiratory Infections? Full Report in PDF format.

"A high percentage of self-reported illnesses occur when elite athletes exceed individually identifiable training thresholds, mostly related to the strain of training" (Foster, 1998). While I'm not an elite athlete, the remainder applies. I exceeded my threshold and gave my nemesis a fighting chance.

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At 7/07/2006 5:03 PM, Blogger Annette said...

I can relate to getting sick when training hard. I recently ran a 1/2 marathon (my first!) denying that I was sick, only to end up at the dr. two days later getting antibiotics. When training ramps up, it tends to happen. If only we could figure out how to avoid that.

Take it easy and get healthy!


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