How it helps: Research has shown that moderate exercise—30 to 90 minutes most days of the week—increases immune function and reduces your chances of catching a cold. Key word: moderate. Prolonged high-intensity exercise can actually make you more susceptible to sickness, according to research from Appalachian State University, in Boone, North Carolina.
Good to know: Don’t swear off workouts if you do get a simple head cold. A 2009 study at the University of Illinois found that moderate exercise can also help you recover from a cold more quickly than normal.