Sick days mean the worst days EVER. Most of us runners have been there. You’re sick but you could definitely push through your run. If you could do it, then why shouldn’t you? I struggle with this every time I get sick, like today for example. Part of this is because I grew up playing sports and you’re coached to play through whatever you can (sickness, injury, etc.).
Non-running friends scold me because the simple and easy answer is that if you’re sick, don’t run. I may be a little stubborn.
In my non-medical opinion, I think that it is best to know your own body. Every runner is different, every day is different and every sickness is different. Exercise can definitely give you an energy boost given that you feel up to going for a run and don’t have severe symptoms. If you do decide to go that route, it is crucial to take it easy and avoid pushing yourself too hard.
That being said, exercising through sickness and pushing yourself too hard also risks making matters worse. Running with a simple cold could turn into a sinus infection (among other things), thus adding more days keeping you from running!
As a good rule of thumb, Runner’s World says, “when in doubt, sit it out“.