Open window theory explains why athletes find themselves sick after a taxing bout of exercise. Let’s take a look at how open window theory was developed.
It started with a notable study led by Dr. David C. Nieman, a professor in the Department of Health, Leisure, and Exercise Science at Appalachian State University, that found 12.2% runners who participated in the 1987 Los Angeles Marathon reported an infectious episode in the week following the marathon versus 2.2% of similarly experienced runners who did not participate in the marathon. The study also found a positive correlation between weekly running mileage and infectious episodes in the two months prior to the marathon.
Dr. Nieman published the aforementioned study looking at infectious rates of Los Angeles Marathon participants and many other studies focusing on the relation between strenuous exercise and infectious disease. In 1994, Dr. Nieman offered a theoretical model for the relationship between exercise and risk of upper respiratory tract infection. The model (see inset) revealed a J-curve relationship between exercise and risk of upper respiratory tract infection. While this model provides a simplified relationship between exercise and risk of contracting an infectious disease, it did not explain biologically why such a relationship exists.
In 2000, Nieman published a follow-up paper in Immunology and Cell Biology that explained how exercise affects the human immune system. The open window theory says that the immune system is weakened for 3-72 hours following extended, strenuous exercise. Monocytes and neutrophils invade the inflamed area that results from muscle injury during exercise. Despite this neutrophilic invasion, the ability of neutrophils to phagocyte foreign invaders has been shown to be reduced following exercise in athletes (Müns 1993). In addition, salivary excretion is reduced up to 18 hours after intense exercise (Steerenberg 1997) demonstrating disruption to the body’s physiology. A 1997 study by Neiman found that natural killer cell activity is reduced after exercise. Cytokine concentration is altered by intense exercise, disturbing the body’s ability to react to and target foreign invaders. Exercise resulting in muscle soreness is linked to a stronger anti-inflammatory response. The alterations in the immune system may be an etiology for the overtraining syndrome, which is responsible for underperformance and mood distrubances in overtrained elite athletes. Nonetheless, exercise has been shown to enhance the immune system's ability to target tumors.
To prevent infectious disease around a taxing athletic event, Dr. Neiman recommends athletes take the following precautionary steps:
- Keep other life stresses to a minimum (mental stress in and of itself has been linked to increased URTI risk).
- Eat a well-balanced diet to keep vitamin and mineral pools in the body at optimal levels.
- Avoid overtraining and chronic fatigue.
- Obtain adequate sleep on a regular schedule (disruption is linked to suppressed immunity).
- Avoid rapid weight loss (linked to adverse immune changes).
- Avoid putting the hands to the eyes and nose (a major route of viral self-inoculation).
- Before important race events, avoid sick people and large crowds when possible.
- For athletes competing during the winter months, influenza vaccination is recommended.