Veronica, I am a firm believer in the "burn it out" theory. I routinely do hard cardio (gym or bike)--I'll be perspiring profusely for an hour. I've been doing this for years and rarely get colds or sore throats, so I assume that my core body temperature rises enough to burn the bugs out.

Someone did a study claiming that people can't raise their body temperature sufficiently high via exercise to kill bugs, but I don't care, I'm still a believer. The study subjects were probably not working out hard enough!!!