Shake the disease

As university student, every semester without fail, I’d get sick a day or so after my last final exam.  I spent many Christmases opening gifts in a fevered haze.  Once I shifted out of overdrive and relaxed for a minute the pathogens invaded.  I seem to have a similar period of vulnerability following marathons, especially when the post-marathon timing coincides with cold and flu season.  This training season is no exception.  Post-marathon I’m reaching my maximum heart rate pouring myself a glass of orange juice.  I think it is some combination of the long walk to the fridge and the strenuous upper body workout that is lifting the juice jug.  I’m not sure if Murphy’s out to get me because I felt so damn good after the race or if running the marathon opened a door to knocking viruses.
 
Anecdotally, many runners report similar post-race experiences with illness; empirically, the evidence of post-marathon changes in the immune system dates waaaay back.  In 1902 Larrabee published work detailing changes in white blood cell counts in four athletes who ran the 1901 Boston Marathon.  Awesomely, he describes the marathon as “violent exercise” and in his words “the severity of the contest will be apparent when it is said that the winner – not included in my four – covered the distance in less that two and one-half hours”.  And in 1901 this violent contest was ‘only’ 25 miles, imagine how he would feel about another 1.2.  He even compares his findings with the runners to those of leucocystosis (medicalese for an abnormal increase in white blood cells) associated with convulsions.  Convulsions!  Surprisingly, the key lesson I (re)learned from Larrabee has nothing to do with white blood cell counts.  Reading this century old work reminded me to Respect the Distance.  Larrabee respected, was awed by, the marathon footrace.  Although becoming more and more commonplace, a marathon is a gruelling event and one must not neglect the need for post-race recovery.  I’m guilty of neglect.
 
More recently, Nieman reviewed his decades long work in the field of exercise immunology and, like Larrabee, concluded that there are significant changes in immune cell concentration and function following marathon-type exertion.  This “open window of immune dysfunction” lasts from three to seventy-two hours (the timing varies across different types of immune measures) increases the risk that viruses and bacteria will infect the race-weary runner.  The end result is an heightened susceptibility to upper respiratory tract infections, such as the common cold.  Nieman found that one in seven runners became sick following the LA Marathon, a surprising number when one considers that only one in fifty runners who trained for the marathon but did not run became sick.  Although it is important to note that a majority of marathoners did not become sick, that’s still a six-fold increase over non-racers.  There is an important connection between training load and infection risk.  During the regular training cycle the risk remains low, but becomes amplified when the runner is over-training or during competition.  Races, in other words, are a risk factor for illness.  The short-term depression in immune function post-marathon is the perfect opportunity for viruses and bacteria to take hold and spread.  And when racing converges with other risk factors, like poor sleep, inadequate nutrition, other stressors, and exposure to novel pathogens illness may result. 
 
Unfortunately, few nutritional or pharmacological strategies to enhance immune function in marathoners have proven effective.  Nieman reports that carbohydrate beverages attenuate some of the negative immunoresponses (e.g. stress hormones) following marathons, but not all immune components benefit.  Companion measures are necessary to minimize susceptibility during this window, but to date – despite a flurry of research around antioxidants and glutamine  - no strong contenders have emerged.  The good news?  People who exercise regularly have fewer sick days over all, pointing to a long-term immune benefit.  It’s in the short-term following exercise beyond typical limits that we need to take extra precautions.  A runner’s best bet is to follow mom’s timeless advice:  get enough rest, eat well, and don’t over do it.
 
 
Title Reference:  Depeche Mode – Shake the Disease.  From the album The Singles 81>85.  1985. 

References:
Larrabee, R.C.  (1902).  Leucocytosis after violent exercise.  Journal of Medical Research, 7, 76-82.
Nieman, D.C.  (2007).  Marathon training and immune function.  Sports Medicine, 37, 412-415.