Running Tips

DOES RUNNING THE MARATHON CREATE AN "OPEN WINDOW?"

The "Open-Window Theory" (1) suggests that running a marathon - or simply engaging in a prolonged bout of running - increases your risk of contracting an upper-respiratory system infection. The basic idea is that protracted exercise "opens a window" for pathogens to sneak through by weakening the immune system in some way. Indeed, some scientific studies have linked drawn-out exercise with changes in white-blood-cell function which would seem to decrease general immunity.

At first glance, the strongest support for the Open-Window Theory was provided by a study carried out several years ago with 2311 individuals who had trained for the Los Angeles Marathon (2). In this investigation, just 2 percent of the runners who prepared for the LA Marathon but did not actually run the race came down with an infection during a specified period after the race, while 13 percent of individuals who actually completed the marathon were stricken.

While this study seemed to suggest that marathon running hikes the risk of infection about six-fold, it was not without its flaws. For one thing, the pre-race incidence of infection was not determined in either group, leaving open the possibilities that 2 percent of the non-runners and 13 percent of the actual runners became ill during a similar time period before the race, too. If that were true, the post-race frequencies of illness would not provide any real support for the Open-Window Theory, because there would be no true increases in the incidence of illness in the two groups.

To find out whether completing a marathon is really tough on the immune system and conducive to pathogen proliferation, researchers from Sweden recently took a close look at 1694 runners who ran the Stockholm Marathon (3).

Their findings may lead to a closing of the Open-Window Theory. During the three weeks leading up to the Stockholm Marathon, 17 percent of the runners came down with an infection. During the three weeks after the marathon, 19 percent of the runners were hit with an infectious episode, but this difference did not come close to being statistically significant.

The Swedish whitecoats did identify some risk factors for post-marathon infection, however. Basically, in the sub-group of runners who experienced an infection during the three weeks before the marathon, 33 percent had problems with infection in the three weeks after the race, a near-doubling of the infection risk, compared with the general population of Stockholm-Marathon runners.

Experiencing nausea during the marathon also heightened the risk of post-marathon infection (for male runners but not females), although the mechanism for this was not detected (it's possible that the nauseated marathoners tended to be the ones who ran the race beyond their capacities, or that the green-around-the-gills runners were more likely to be dehydrated; these two factors might downgrade immune-system activity).

Younger (under-40) runners were more likely to become infected after the marathon (one advantage of being a Master), but they were also more likely to get sick before the race. Contrary to popular belief, training volume before the race was not linked with the risk of infection; the high-volume runners did not get sick more often, compared with the 25-K-per week runners. Similarly, finishing time did not predict infection. 2:30 marathoners were not more likely to become ill, compared with four-hour-plus individuals.

What are the bottom lines in this new research? First, running a marathon does not seem to heighten the risk of being hit with an infection during the post-race period. Secondly, if you come down with a respiratory system infection during the three-week period leading up to a marathon, you should exercise caution. Running a marathon within three weeks after coming down with an infection will dramatically increase the risk that you will get sick following the race, too.

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References

(1) Sports Medicine, Vol. 19, pp. 393-400, 1995
(2) Journal of Sports Medicine and Physical Fitness, Vol. 30, pp. 316-328, 1990
(3) Scandinavian Journal of Medicine & Science in Sports, In Press, 2006


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