Listening to old wives tales, when you are sick, you should stay in bed all day, drink chicken soup and avoid any sort of physical exertion. In my experience, the opposite is true. Especially for common colds. In my case I have found that rigorous exercise, whether it's jogging or capoeira in my case, can often kill a cold. I guess it has something to do with sweating it out.
The cold I have right now, sadly, is not such a cold. It could be the flu, I don't know. All I know is that it was probably caused by lack of sleep last week. It attacks my throat and lungs, and after a class or so, it becomes hard to speak for a long time without drinking something. But it doesn't take too much out of me.
The proof is that I went on a HHH run yesterday and could jog the whole thing (well, except the steep uphills, which I never jog whatever my condition). It was a fairly long one too, and the first half or so was wonderful. From Shinkaichi station we climbed to a reservoir in Hyogo ward, Kobe, before running down a riverside, crossing the JR line and running parallel to the Chinatown. The run finished at the Kobe Regatta Athletic Club, where the HHH was first introduced in Kansai.
The run was very good, and even if I was not running at my regular pace, I kept a good one throughout and my cold never hampered me. When I finished, though I could feel a little burn in my lungs, but it didn't last long.
So the next time you think about skipping a run because you are sick, why don't you think about how sick you are. Yes, if you have a really bad condition, exercising is probably not recommended. But if you only have a little cold, I suggest you try; it could do you more good than bad. Even with my 'bad' cold, I don't think I feel worse today than I would have if had not jogged. I could ride my bicycle to and back to work with a heavy bag on (photo shoot before w*rk today) and I still feel fine tonight.