text: Should You Exercise When You're Sick? | Men's Fitness
  A sore throat, achy muscles and a runny nose can make you miserable, but if you still have the energy to exercise, should you? Aside from infecting everyone else at the gym, what's the real danger? The good news: Fit people recover from illnesses quicker and experience milder symptoms than couch potatoes, according to a 2011 study in the British Journal of Sports Medicine. Raul Seballos, M.D., vice-chair of the department of preventive medicine at the Cleveland Clinic, suggests the following guidelines for exercising before, during and after a cold or flu.
  A: If you feel like you're coming down with a garden-variety cold, you can still exercise without significant limitations. If you begin to feel worse after your workout, however, cut back. Take a few days off or reduce your effort to 50% of your normal capacity. Walk for 15 minutes instead of running for 30 minutes, or do one set of lifting instead of five. Also keep in mind the above-the-neck rule: If your symptoms include a runny nose, dry cough, or sneezing, you should be fine to exercise. But if your symptoms are below the neck, such a chest congestion, muscle aches, upset stomach, etc., make sure to rest.
  A: Again, listen to your body. Colds typically last for a week to 10 days, but you may need as many as two to three weeks to recover from the flu, depending on the severity. Don't go 100% for the first three or four days. Start at 75% of your normal workout (for both cardio and weights) and increase gradually for the first week or so. If you try to go back too soon, you may just end up prolonging recovery phase. You may also be more short of breath if you're recovering from an upper respiratory infection.