Don’t exercise when you’re sick—unless your symptoms are above the neck. And even then you might do better taking a day off. Your body will use its resources to heal itself, not build muscle and endurance. The immune system is busy trying to defend against the virus. In some cases exercising during periods of having a cold can weaken the immune system to the point where a common head cold ends up becoming a bronchiorespiratory issue, bronchitis or in severe cases walking pneumonia. It is better to reduce the exercise to help boost immunity but not to do too much that it hinders immunity. You won’t lose anything from taking a couple extra days off.
Daryl Conant, M.Ed