Some flu symptoms include: fever, muscle and joint pain, sore throat, coughing and sneezing, nasal congestion. The main reason doctors ask a person to stay in bed when experiencing the flu is to relieve fever and muscle and/or joint pain. This is because fever causes general weakness in the body. On the other hand, not resting keeps the muscles busy, and further increases pain. So, most doctors and researchers agree that rest in bed is recommended during the time these symptoms are present. In severe cases of flu, a day or two more in bed might prevent complications.