Two studies were published over a decade ago that showed results that surprised researchers. The studies showed no difference in symptoms between those who exercised and those who didn?t. And there was no difference in the duration of the colds between the two groups. When symptoms were assessed, in some cases those who exercised said they felt better.
The result of these studies are in no way meant to encourage people to train when they’re sick. The studies tested subjects who had head colds. One needs to be more cautious when dealing with a cold or other illness that produces fevers or other symptoms like chest congestion.
The rule of thumb is: If you have symptoms above the neck it?s OK to workout. Below the neck, forget it.
Edit: In the third paragraph, the mistake “their” was changed to the correct “they’re”.