Causes of marathon flu
Athletes who participate in strenuous endurance exercise may experience a decrease in immunity, and “vigorous exercise” is associated with increased symptoms of upper respiratory tract infections. This response can be due to several factors, including the environment, genetics, physical and mental stressors, and underlying health conditions.
Dr. Ian McKeague, associate professor of family and community medicine at the University of Alabama at Birmingham School of Medicine, explains how intense exercise (such as running 42.2 miles at a time) affects the body.
“When you’re running a marathon or even a half-marathon, you’re under a lot of physical stress,” he says. “You use up all kinds of energy, you use up glucose and glycogen. Your body can only really function for about an hour before it starts taking energy from other sources. When you start taking energy from some of those sources, it puts more demands on your body as a whole.” Your immune system is weakened and your risk of getting sick increases.
Also, many changes occur in your hormones during training, which can cause problems.
“When you’re training for a marathon and you’re constantly putting that kind of stress on your body, things like cortisol levels change,” Dr. McKeague says. “Stress hormones can negatively impact your immune response and may be one reason why your immune system doesn’t get as strong after a long distance run.”
Another big factor is exposure to bacteria.
“On race day, runners are placed in a corral full of other runners, which creates a bottleneck for the first few miles of the race,” says McKeag. “You will be exposed to a large and diverse group of people.”
Coviello agrees, pointing out that athletes could be exposed to infectious bugs while traveling to races.
“And in a race, when your immune system is already compromised, you have a lot of different germs around you,” she says. “Then there are people throwing snot rockets all over the place. And at the end of the race, we’re all covered in snot and sweat and we’re all hugging each other.”
