Exercise reduces a cold's symptoms and severity

LiveScience - Exercise makes the common cold less common

In this study, researchers asked people to report on how fit they felt, how often they exercised, and how long their sicknesses (e.g. colds) lasted. Those who exercised more often (or at all) had shorter durations for cold symptoms, and they were less severe. Interestingly older people got sick less, as did married people. The theory is that exercise helps distribute immune cells throughout the body.