Researchers studied 160 overweight, sedentary women ages 18 to 85. Half walked for 45 minutes five days a week for 12 to 15 weeks, while the other half remained sedentary.
Result: The walkers who got colds had 4Oo/o to 5O%o fewer days of illness than non walkers who got colds.
Theory: Thirty to 60 minutes a day of moderate exercise, such as walking at a 15-minute per- mile pace, spurs production of germ-killing cells called neutrophils. Caution: Ninety minutes or more of high intensity daily exercise, such as long-distance running, has the opposite effect, increasing stress hormones and immune dysfunction.
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