A new study revealed that people who exercise regularly experience shorter, less severe cold symptoms compared with sedentary people. They study followed about 1,000 adults for a 12-week period during the cold-catching season, comparing their health to their fitness track record, and analyses showed that the people who broke a sweat for 20 minutes at least five times a week spent 43 percent less time being sick compared with the exercise slackers. The active folks’ cold symptoms also tended to be about a third less severe. How does a good sweat make people more immune to colds? It’s all about aerobic exercise. This type of exercise seems to ramp up blood vessels of neutrophils and natural killer cells, two cell types critical to immune system operations.