Exercise and Immunity: Staying Healthy During the Off Season

Written by Holly Ortlund, M.S., Director of R&D, Carb-BOOM, Inc.

Introduction

Like it or not the flu and general ëcold weather crud' season is here. Some of you may have stored your bicycle away in the garage for the winter while others look to take advantage of the slow cold months by building up a strong endurance base in preparation for next season. Whether you're out logging in tough running/cycling/swimming workouts or just serving your role as weekend warrior, read on for a brief overview of how you can help stay healthy during the winter season.

Background

The average adult experiences between 2-5 cases of ëthe common cold' per year. The medical community often uses the terms ëcommon cold' and upper respiratory tract infection (URTI) interchangeably to diagnose systems that include coughing, aches and pains, fever, headache, and nasal congestion.

A number of studies within the past decade have shown that individuals exercising moderately exhibit a lower incidence of URTI's compared with the sedentary population; whereas individuals involved in strenuous activity actually exhibit an increased risk of infection (See Figure 1) (3,4,6). This relationship between exercise and URTI is thought to be a direct result of alterations that occur within the immune system during and after physical activity.

So what does this mean to you as an athlete? High intensity exercise comprises a large proportion of the competitive athlete's training regimen. A brief period of immunosuppression (which may last between 3 and 72 hours) has been frequently documented to follow a strenuous bout of exercise. It has been proposed that during this ìwindow of opportunityî sufficient time is available for micro-organisms and viruses to become established within the body (5). In other words, during periods of heavy training or after a particularly strenuous workout/event your immune system may be operating at less than optimal levels, thereby putting you at risk for getting sick.

Strategies to combat risk

The good news is that there are ways you can decrease your risk of catching an infection. A good place to start may be more obvious than you think: carbohydrates. Carbohydrate ingestion lessens the hormonal and immune responses related to exercise stress that may result in decreased immune function, thus likely providing a protective effect.

In more detail, strenuous exercise activates the release of stress hormones into the bloodstream which include adrenocorticotropin hormone (ACTH), cortisol and catecholamines (epinephrine and norepinephrine). Various immune cell populations are sensitive to elevated levels of these stress hormones and one factor that is partly responsible for their release is a low concentration of blood glucose. It is well known that carbohydrate ingestion prior to and throughout exercise maintains normal levels of blood glucose and consequently suppresses both the amount and length of time that stress hormones are present in the bloodstream (1,2,7,8,9). It therefore follows that negative changes in the immune system may also be diminished.

So, in addition to making sure your carbohydrate intake is sufficient before, during and after your next tough workout here are some other suggestions on keeping your immunity in top form:

• Eat a well balanced diet.
• Keep life's stresses to a minimum. Psychological stress has been associated with decreased immune function.
• Stay hydrated. Dehydration often occurs during and after exercise and can also suppress immune function.
• Avoid over training. Space intense workouts as far apart as possible to allow for adequate recovery.
• Get plenty of sleep.
• Try to avoid contact with sick people immediately before and after an event or particularly strenuous workout. If symptoms of illness appear, decrease the intensity and duration of workouts or skip training altogether.

Summary

To recap, athletes have a 2-6 times greater risk of contracting URTI's as compared to controls during the 1-2 week period following strenuous competition or training. When additional stressors such as poor diet, lack of sleep, and psychological stress are also present this risk can be further increased. One simple strategy that can counteract this immunosupression is the ingestion of carbohydrates during and after activity. So, while heading out for your next hard workout, make sure to take along some gels (or other source of carbohydrates); they will not only aid you in training harder but will also help you stay healthy.

References:

1. Davis, J., Cokkinides, V., Burgess, W., Bartoli, W. Effects of a carbohydrate-electrolyte drink or water on the stress hormone response to prolonged intense cycling: rennin, aniotensin I, aldosterone, ACTH and cortisol. In: Z. Laron, Rogol, A., editors, Hormones and Sport, Raven Press, Vol. 55: 193-204, 1989
2. Deuster, P., Singh, A., Hoffmann, A., Moses, F., Chrousos, G. Hormonal responses to ingesting water or a carbohydrate beverage during a 2 h run. Med Sci Sports Exer 24(1): 72-79, 1992
3. Heath, G., Ford, E., Craven, T., Macera, C., Jackson, K., Pate, R. Exercise and incidence of upper respiratory tract infection. Med Sci Sports Exer 23:152-157, 1991
4. Linde, F. Running and URTI. Scand J Sport Sci 9:21-23, 1987
5. Mackinnon, L.T. Immunity in athletes. Int J Sports Med 18:S62-68, 1997
6. Nieman, D., Johannsen, L., Lee, J., Arabtzis, K. Infectious episodes in runners before and after the Los Angeles Marathon. J Sports Med Phys Fitness 30:316-328, 1990
7. Nieman, D., Henson, D., Garner, E., Butterworth, D., Warren, B., Utter, A., Davis, J., Fagoaga, O., Nehlsen-Cannarella, S. Carbohydrate affects natural killer cell redistribution but not activity after running. Med Sci Sports Exer 29(10):1318-24, 1997

    
8. Nieman, D., Fagoaga, O., Butterworth, D., Warren, B., Utter, A., Davis. J., Henson, D., Nehlsen-Cannarell, S. Carbohydrate supplementation affects blood granulocyte and monocyte trafficking but not function after 2.5 h or running. Am J Clin Nutr 66(1):153-9, 1997

    
9. Nieman, D., Nehlsen-Cannarella, S., Fagoaga, O., Henson, D., Utter, A., Davis, J., Williams, F., Butterworth, D. Effects of mode and carbohydrate on the granulocyte and monocyte response to intensive, prolonged exercise. J Appl Physiol 84(4):1252-9, 1998

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