»Believe it or not, rigorous exercise can weaken a person’s immune system«
By David C. Nieman*, DrPH, FACSM, professor and director of the Human Performance Laboratory, Appalachian State University, in Boon, published in September 2006
QUESTION:
I ran hard for two hours last weekend and two days later came down sick with a terrible cold. Did my running bout suppress my immune system and cause my cold?
ANSWER:
Yes, running hard for 90 minutes or more causes a downturn in immune function, increasing your odds of getting sick. Regular moderate exercise improves immunity, but when exercise is pushed too far, then immunity declines.
These reports parallel findings from studies of large groups of athletes. For example, during the week following the Los Angeles Marathon race, my research team showed that one out of seven runners came down sick. The illness rate was nearly six times that of runners who had trained for but did not run the marathon. During the two-month period before the race, runners training more than 60 miles a week doubled their odds for sickness compared with those training less than 20 miles a week.
Research in my Human Performance Laboratory at Appalachian State University has shown that athletes exercising at high intensity for 90 minutes or more experience a steep drop in immune function that lasts at least six to 24 hours.
Much of this immune suppression appears to be related to the elevation of stress hormones, which are secreted in high quantity during and following heavy exertion. This temporary drop in immune function allows viruses already in the body to spread and gain a foothold.
You and other athletes must train hard to compete, so avoiding heavy exertion is not an option. To lower risk of immune suppression and sickness during heavy training and after competition, I recommend that endurance athletes such as distance runners, cyclists, triathletes and swimmers follow these guidelines:
- Keep other life stresses to a minimum. Mental stress in and of itself has been linked to an increased risk of upper respiratory tract infection.
- Eat a well-balanced diet to keep vitamin and mineral pools in the body at optimal levels. Don’t rely on nutrient supplements. My research has shown that supplements such as vitamin C and E do not prevent post-exercise downturns in immune function.
- Avoid overtraining and chronic fatigue. Athletes are most susceptible to sickness and immune suppression when overtrained.
- Sleep on a regular schedule. Sleep disruption has been linked to suppressed immunity.
- Avoid rapid weight loss (which has also been linked to negative immune changes).
- Avoid putting hands to the eyes and nose (a primary route of introducing viruses into the body). Before important race events, avoid sick people and large crowds when possible.
- For athletes competing during the winter, flu shots are recommended.
- Drink beverages before, during and after race events or unusually heavy training bouts.
- May I add our experience with biestmilch here: Take biestmilch on a regular basis to stabilize your immune system. I recommend the standard amount of 900mg daily.
Multiple studies in the ASU Human Performance Lab have shown that ingestion of carbohydrate beverages during prolonged and intense exercise keeps levels of blood sugar high and stress hormones low. The result is diminished immune suppression and inflammation.
Some endurance athletes have robust immune systems that can handle substantial training workloads, while others break down at much lower training thresholds. You must find your own training threshold and avoid overreaching into the zone of immune suppression and increased sickness rates.
*Professor Nieman is one of the protagonists in immune research related to physical activity. He was among of the first who recognized the importance of the immune system for endurance performance.
