Close That Window: Infection Risk Following Strenuous Exercise
by Bob Albright, D.O.
“Write about what you know” -- that’s what they say. Well, I have a case of the crud right now. I have a garden variety upper respiratory infection. This current bug has led to sore throat, fatigue, achiness and amazing amounts of nasal secretions.
I tend to get these a lot -- perhaps many of you do too -- as the literature seems to suggest a “J” shaped curve for upper respiratory infection risks (URI). The risk for URI is modest for sedentary folks, decreasing among regular exercisers, which was defined as three to four times per week. Then an increased risk of infections is noted among those who exercise daily at a “strenuous” level; even having rates exceeding the sedentary folks. Hmmm.
We have all also heard about the worst places to pick up infections: gyms. This may have led investigators from Queensland, Australia to investigate a possible “window” of time following acute strenuous exercise when we may be vulnerable for infection, and when the immune system may return to normal.
The study evaluated immune function among 10 grade “A” cyclists who exercised for two hours at 90% of their secondary ventilatory threshold. Their white blood cells (WBC) were collected and characterized by type, and better yet, by functional activity. Measures of the neutrophil respiratory burst (the secretion of chemical toxins by the WBCs to kill bad guys), phagocytic function (ability to eat the bad guys) and chemotaxis (the ability to hone in on the bad guys) were collected at baseline and at two, four, six and eight hours post exercise.
The results illustrated an impressive decrease in the function of the immune system which was worst at two hours but extended to eight hours. The degree of dysfunction seemed to lessen as time went on.
This data squares with retrospective cohort trials of long-course triathletes, which suggest a dramatic increase in infections for the weeks following the event. Perhaps suggesting the dose of the exercise may have a relationship to the duration of decreased immune function.
Getting back to my current status -- as it’s all about me of course…
I blame the gym -- well, okay, maybe me more than the gym!
This has been a particularly tough winter for most of us, excepting our friends in the Netherlands, Northern Canada, Greenland, Iceland... Many of us have been forced inside beyond what might be reasonable.
While I have fastidiously wiped the equipment down following my workouts, I have always looked askance at those around me furiously wiping the equipment -- especially the spin bikes -- before their workout. I used to mutter OCD under my breath in a somewhat self-satisfied fashion.
So take control. Close that window!
Warm winter regards
Kakanis, MW, et al. The open widow of susceptibility to infection after acute exercise in healthy young male elite athletes. Exerc Immunol Rev. 2010;16:119-37.
Bob Albright, D.O., is a Nephrologist and Assistant Professor of Medicine at the Mayo Clinic in Rochester, Minn. You can contact him at firstname.lastname@example.org.