Exercise and the Immune system

Exercise and the Immune system　Ｄ.Ｌ.Ｖａｕｇｈａｎ

Does regular, moderate exercise decrease our chance of coming down with a cold or flu?

Several studies involving mice and humans suggest the answer to this question is a resounding “Yes!”. 

Here is the mouse data: 

(University of Illinois-2005) Three groups of mice were intentionally infected with a virus. 

Group #1: (Moderate exercise) 20-30 minutes per day▶︎▶︎Survival rate 82%

Group #2: (No exercise) Sedentary▶︎▶︎Survival rate 43%

Group #3: (Extreme exercise) 2 1/2 hours per day▶︎▶︎Survival rate 30%

CONCLUSION: Regularly exercising mice survive flu virus infections significantly better than sedentary mice. Over exercising can have a negative impact. 

One obvious question is how to translate the mouse “moderate exercise” into human terms. But certainly the 30 minutes of aerobic exercise per day, recommended by most health organizations, matches the “moderately exercising” mice. 

When following 2,300 runners preparing for the Los Angeles Marathon, only those who trained 95K per week or more, were at elevated risk of catching a cold. So jogging an average of 13-15K per day might negate the positive effects of exercise on the immune system.

Another interesting mouse study (Iowa State University-2009) showed that the benefits of exercise on the immune system were immediate, occurring after one single session. Again 3 groups of mice were inoculated with a flu virus, this time looking at the duration and severity of symptoms.

Group #1: Moderate exercise x 14 weeks.   These mice had the fewest symptoms and the quickest recovery  times. 

Group #2: Sedentary. Not surprisingly, these mice had the most severe symptoms, lasting the longest. 

Group #3: Sedentary, except for one 45-minute session of treadmill exercise, 15 minutes immediately before the flu virus inoculation.  Symptoms were markedly diminished, although not quite to the degree of the regular exercising mice. 

But current evidence points to the immediate benefits of a single session of activity, done before exposure to potential infections (air flights, conventions, etc). You might want to plan a stimulating 30-minute jog or fast walk, the day before or the morning of your next flight! (Fascinating ongoing research in humans related to the positive effects of single-session exercise on the immune system will be featured in an upcoming article.)

The University of South Carolina studied >500 regular exercisers, finding 20% fewer colds in this group compared to sedentary individuals. 

During this Covid-19 pandemic, we need to add “EXERCISE” to the list of habits and measures that are very likely to reduce our risk of becoming infected with severe disease.