THE QUICK AND DIRTY
Consistent exercise can help build and maintain a healthy immune system and reduce your chances of getting sick.
Very long or extra-hard workouts can weaken the immune system for a short period of time.
If an illness is above the neck, it is ok to exercise while sick (within reason) but if the illness moves below your neck, rest is best.
— Read on www.quickanddirtytips.com/health-fitness/exercise/should-you-exercise-while-sick