First, figure out your symptoms to see whether or not you should stay in bed. In general, a sickness that causes above-the-neck symptoms — like a headache, congestion, or a runny nose — means you can exercise. Any flu-like symptoms like aches or pains, chest congestion, nausea, or a fever, means you should stay away from your fitness gear until you feel better.
Even if you are OK to exercise, keep things light to avoid overextending yourself. If you have a cold or are congested, exercise at half your regular intensity and gradually increase until you are at 80 percent (reduce intensity if you still aren't feeling well). Yoga may help both migraines and headaches; check out this yoga sequence for relieving tension headaches.
