Vigorous exercise during the incubation period of a viral illness may increase the duration and severity of that illness. Athletes who feel as if they are developing a cold should rest or reduce the training schedule for a few days. In conclusion, the prevailing wisdom is that it is better to be undertrained than overtrained. Rest is a vital part of any athlete's training. A well-planned training program involves as much art as science and should allow for flexibility.
Smart training is the path to faster times and good health.