Regular exercise keeps your immune system working optimally. People who exercise regularly tend to be healthier and experience fewer colds then those who do not; they also tend to recover from colds faster. I am often asked if it is a good idea to exercise while fighting a cold. Exercise increases lymphatic drainage and circulation aiding the immune system; it also improves sleep quality which is important component to healing. Most people are contagious for the first 5-7 days so it is best to stay away from public spaces during this time, especially as cold viruses can live on hard surfaces for several hours. Prevent the spread of these viruses by staying home, frequently washing your hands, and sneezing into a tissue or your elbow crease. If you have mild symptoms (runny nose, sneezing) or are in the recovery phase, keep your heart rate below 120 bpm and start at 50-75% of your normal capacity. Jumping back into 100% performance can prolong the recovery phase post cold.
When to stay at home: if you have a fever, abdominal symptoms (diarrhea, vomiting), severe fatigue, muscle fatigue/weakness/pain, shortness of breath, or a productive cough (increased mucus production).
For more about preventing and treatment of colds and flus, read this post.