Does exercise stress alter susceptibility to bacterial infections?

Swimming was used for evaluating alterations in performance capacity and as a means for studying the influence of exercise stress on susceptibility to Streptococcus pneumoniae and Francisella tularensis infections in two strains of rats, i.e. Fisher-Dunning (FD) and Sprague-Dawley (SD). The performance capacity was reduced by both diseases and was correlated to the dose of the given micro-organism. FD rats, however, were more susceptible to the infection and showed a greater deterioration than SD rats. The effects of exercise stress on disease lethality varied with the time that it was performed. Strenuous exercise immediately before infection drastically reduced susceptibility to either of the bacteria, while a similar bout of exercise performed after infection increased disease-related mortality in both diseases.