What athlete has not asked this question? What cyclist has not heard the philosophy of "train if the illness if above the neck and rest if its below"? Sometimes its easy to make the decision, like when its 19 degrees and raining. However, can and should cyclist rest when fighting even a mild sickness?
Let's think about mild head colds. The reason for this is that I believe most athletes would rest if faced with a fever, flu or symptoms extreme enough to really force them to bed. When you think about the start of a head cold, you are really just talking about a little congestion, sore throat maybe from nasal drainage, sinus pressure, headache and slight fatigue. Not enough to really keep you off the bike, but maybe it should be.
At the beginning signs of an illness, we do a lot of things to try and combat it. Extra Vitamin C, maybe some zinc or the now so common cold protectors like "Airborne" and EmergenC". We probably also go into a mode of hydrating ourselves beyond normal range and rest when we can. What if we have a hard ride to do though? Or what if you are on the final week of a base building program and you have to hit the numbers on your training program?
Here is the bottom line: Exercising in the early stages of an illness increases the chances of it progressing. Exercising in the later stages when you just have lingering effects (usually above the neck) can help relieve those symptoms. Besides, can you give your training the full effort when fighting a sickness. It is advised to shift your training slightly, maybe take an early rest week or put off the last week of base training. Its better to rest now and be able to give your training full effort in a few days then to try and push through and extend your sickness by a few weeks.
That being said, can I take my own advice. This little head cold is not bad. I think I could fight it quickly so it feels odd to stay off the bike because of it. However, I know that my interval training would not be up to par and my long rides outside would compromise my immune system.
Looks like I will be shifting my training slightly.