Why does running a half or full marathon increase susceptibility to colds?
There is a large body of research that shows that moderate exercise reduces the incidence and severity of a cold or flu but intense or prolonged exercise increases the risk and severity of infection.
The research we found most relevant to runners and endurance athletes was conducted by noted exercise immunologist, Dr. David Nieman, Director of the Human Performance Laboratory at Appalachian State University. (Lance Armstrong has worked with Dr. Neiman and has been tested in his lab). Dr. Neiman found that running or cross-training 30 to 90 minutes a day several times a week strengthened the immune system. However, exercise longer than 90 minutes increased risk of infection.
What happens after 90 minutes of exercise? “When you’re running for 90 minutes or longer, there’s a temporary downturn in immunity” says Dr. Nieman. “Around the 90-minute mark, carbohydrate stores drop, causing a spike in two key hormones, cortisol and epinephrine. This, in turn, inhibits those neutrophils and lymphocytes (immune cells that fight infection) leaving you vulnerable to nasty bugs.”
This conclusion mirrors Bennett’s own experience. In 2007, after a training period which had lasted 20 weeks, he reviewed his running log and noticed that on five occasions, he had written that he felt like he was coming down with a cold. Every entry was written on a Tuesday, following a Sunday long run or race. Hardly a coincidence!
A study by Dr. Nieman of the 2,311 finishers of the Los Angeles Marathon showed that 13% developed an upper respiratory tract infection the week after racing. Another study of marathon finishers involving 1,694 runners at the 2000 Stockholm Marathon revealed that almost one in five contracted a cold or other infection within the period three weeks prior to three weeks after the race.
Keeping things in perspective,
although the risk of catching a cold after a long hard run or race is elevated, the vast majority of runners do not fall ill
Here are four action steps to enhance your immune system and reduce the risk of post-race (or post-long run) infection:
1.Take in carbohydrates immediately before, during and after racing. Carbohydrates keep your stress hormone levels and inflammatory markers under control, which reduces the risk of infection
2.Get plenty of extra rest. Take an afternoon nap and get extra sleep during the nights following your race. Immunity boosting growth hormones are released during sleep. Research shows that the highest levels of killer cells that fight infection are produced after eight hours sleep.
3.Taking Vitamin C and Echinacea may provide additional support for your immune system.
4.Quercetin supplementation is being studied is a means to bolster the immune system. Quercetin is a phytochemical found in red apple skins and red onions. In an initial study published in the American College of Sports Medicine, it was found to reduce the incidence of upper respiratory tract infections in cyclists following intense prolonged exercise. One study does not make for a scientific conclusionâ€¦â€¦â€¦. but stay tuned.
Of course, following generally accepted health guidelines such as washing your hands frequently and sneezing/coughing into your upper sleeve (instead of your hand) make especially good sense.