Can Too Many Miles Make You Sick?

Understanding How Stress Affects Your Immune System

Norm Klein was worried—worried about the health of some of the athletes he and his wife Helen had come to know as friends and fellow competitors during Norm’s 14-year tenure as race director of the Western States 100. "It was after I was no longer race director, in 2000, that I started observing what I believed was a cancer trend in runners who had competed over the years in the event," Klein says. The 20 athletes he refers to are or were all residents of northern or central California and northern Nevada; 15 men and five women, two of whom are now deceased.

Klein, a former surgeon, explains that it "seemed unusual that people in such excellent physical condition would be developing cancer." The majority of the cancers in the male runners were cancer of the prostate, while the women developed various unusual and rare forms of the disease. "The man who died was our best friend; he died 16 months after his prostate cancer diagnosis. The woman, who was in her mid-40s, died of a particularly vicious cancer that produced tumors and lesions throughout and all over her body. She was dead within a few months after winning the women’s division of the Rio Del Lago 100."

Was it possible that there was a connection between the high mileage these runners had maintained over the years and their developing serious, even terminal illnesses? Klein wanted to find out, so he called on Dr. Robert Lind, at that time the medical advisor to the Western States 100, for help. Upon hearing of Klein’s observations Lind was quickly caught up in the medical mystery and became equally determined to understand what was happening within the runners’ bodies.

The Complex Immune System

"Even though what Norm was telling me was anecdotal, I knew that something had to be going on. Since I was the medical advisor to the race I was familiar myself with many of the athletes’ health concerns. It seemed that there might be a connection between immune system dysfunction and the stresses runners endure when training for and competing in ultradistance events. But we had no proof," says Lind. "So I started searching for people who might be interested in pursuing a possible connection."

In 2001 Lind came upon an article written by Dr. David Nieman, Professor of Health and Exercise Science at Appalachian State University in Boone, North Carolina.

Nieman, a veteran of over 50 marathons and ultra events, had done extensive research on the pre- and post-race health histories of participants at the City of Los Angeles Marathon. What he learned, and had written about in the article, was that runners who trained more than 60 miles per week doubled their chances of getting sick in the days and weeks following the race. "This was exciting because it seemed to indicate that there was a real connection between strenuous training and illness. I contacted Dr. Nieman late that year about what we had observed in runners at Western States. As a result, through funding generated by the event participants, Gatorade and the Department of Defense, Nieman has been studying the effects of immune system response to stress caused by training for and competing in the Western States 100 ever since."

Lind explains that it’s because the immune system is so complex that few studies had been done prior to Nieman’s research. "Immune dysfunction is caused by five triggers: stress, infections, toxins, deficiencies and trauma. We’re only just beginning to learn how each of these triggers can affect the immune system, and in athletes we’re trying to understand what makes some of them more prone to illness than others. It’s like a superimposed type of stress that causes more problems for some runners."