Objective Limited data imply an inverse relationship between physical activity or fitness level and the rates of upper respiratory tract infection (URTI). The purpose of this study was to monitor URTI symptoms and severity in a heterogeneous group of community adults and contrast across tertiles of physical activity and fitness levels while adjusting for potential confounders.

Design A group of 1002 adults (ages 18–85 years, 60% female, 40% male) were followed for 12 weeks during the winter and fall seasons while monitoring URTI symptoms and severity using the Wisconsin Upper Respiratory Symptom Survey. Subjects reported frequency of aerobic activity, and rated their physical fitness level using a 10-point Likert scale. A general linear model, with adjustment for seven confounders, was used to examine the effect of exercise frequency and fitness level on the number of days with URTI and severity of symptoms.

Results The number of days with URTI during the 12-week period was significantly reduced, 43% in subjects reporting ≥5 days/week aerobic exercise compared to those who were largely sedentary (≤1 day/week) and 46% when comparing subjects in the high versus low fitness tertile. URTI severity and symptomatology were also reduced 32% to 41% between high and low aerobic activity and physical fitness tertiles.

Conclusions Perceived physical fitness and frequency of aerobic exercise are important correlates of reduced days with URTI and severity of symptoms during the winter and fall common cold seasons.