Smoking, alcohol consumption, and endurance capacity: an analysis of 6,500 19-year-old conscripts and 4,100 joggers

Using data from two Swiss studies, a 20% random sample (n = 6,592) of all 19-year-old army conscripts and all male participants in a 16-km popular race (n = 4,358), we studied the relationships among smoking, alcohol consumption, and endurance capacity using univariate and multivariate analyses. Alcohol was significantly correlated with endurance capacity among joggers in univariate analysis, but lost its significance in multivariate analysis. Among army conscripts, the distance covered in a 12-min endurance run was inversely related to daily cigarette consumption and years of smoking (P less than 0.001). This association was apparent even among light smokers who had been smoking for less than 2 years when they were compared with nonsmokers. Among joggers, even when the lower training activity of the smokers was controlled for, smoking retained a negative, independent association with endurance capacity, as measured by 16-km race time. In multiple regression analysis of endurance capacity, the standardized regression coefficient for smoking was -0.14 for distance covered in the 12-min run and 0.10 for 16-km running time, the latter despite the low prevalence (6.9%) of regular cigarette smokers among the joggers. Seventy percent of the 16-km race participants who smoked around the time they took up jogging quit smoking as joggers. Within the limits of this cross-sectional study design, these results suggest that smoking exerts a direct, biologically mediated, deleterious effect on endurance capacity. The lower levels of exercise of the smokers did not entirely explain the difference in endurance between smokers and nonsmokers. This observation of a short-term negative association between even light smoking and endurance capacity may have implications for health education and promotion efforts.