An association between aerobic fitness and lung closing volume

This study was performed to determine whether an association exists between relative aerobic fitness (fitness index) and lung closing volume (CV). The subject population consisted of 100 healthy nonsmoking adults (50 males and 50 females) divided equally into five age groups; 20-29, 30-39, 40-49, 50-59, and over 60 years. Each subject underwent four to six closing volume and forced vital capacity (FVC) tests followed by a modified Balke maximal oxygen uptake test on a motor-driven treadmill with a constant treadmill speed. Relative VO2 maximum (VO2 max, mlO2 X kg-1 X min-1) was determined from the exercise test and was used to define subject rank on the fitness index. CV, as a % of slow vital capacity (SVC), had a negative linear correlation (r = -0.53, P less than 0.05) with the fitness index. Slope of phase III (%N2/L) and FEV1/FVC (forced expired volume in 1 s as a % of forced vital capacity) also had significant correlation coefficients (r = -0.31, r = 0.24, respectively; both P less than 0.05) with the fitness index. The correlation coefficients, with age partialled from the relationships, between FVC/body weight (kg) and VO2 max were r = 0.59 for females and r = 0.43 for males (P less than 0.05, both groups). We hypothesize that the effects of aerobic fitness on lung function may be the result of changes in autonomic nervous system activity and may represent a situation where a high level of aerobic fitness affects the aging process of the lung beta-adrenergic nervous system.