A recent article in the New York Times cites a study from last year which was published in the journal Brain, Behavior and Immunity. In this study, researchers divided mice into 2 groups. One of the groups rested comfortably in their cages for 3 days. The other group was forced to perform extremely strenuous exercise for 3 days. Then both groups were exposed to the influenza virus. More of the exhausted mice came down with the flu and had more severe symptoms than the mice who rested.
So does it pay to be a sloth? Not quite. Researchers at the University of Illinois compared immunity patterns of 3 distinct groups of mice. The first group was sedentary,the second group did moderate exercise and the third group did strenuous exercise. The mice were then exposed to the flu virus. About half the sedentary mice died. A whopping seventy percent of the strenuous exercising mice died. But only 12 percent of the moderately exercising mice died.
This evidence suggests that there is a “J” curve when it comes to the benefits of exercise on the immune system. A sedentary lifestyle and extreme exercise are both detrimental. Moderate exercise, however, is beneficial and can actually boost one’s immunity.