EFFECTS OF GENDER AND FATIGUING EXERCISE ON SUSCEPTIBILTY TO RESPIRITORY INFECTION

Abstract

Fatiguing exercise increases susceptibility to respiratory infection following intranasal inoculation with herpes simplex virus-1 (HSV-1) in male mice (Davis et al., J.Appl.Physiol., 83(5): 1461–6, 1997). Although there may be gender differences in susceptibility to certain pathogens, it is unknown whether female mice will respond differently than males in response to strenuous exercise and HSV-1 infection. PURPOSE: To test the effects of gender and repeated exhaustive exercise on susceptibility to HSV-1 infection. METHODS: Male (n = 58) and female (n = 60) CD-1 mice (60 d old) were randomly assigned to exercise (Ex) or control (C) groups. Exercise consisted of 3 days of running at 36 m/min 8% grade until volitional fatigue. Fifteen min following the last bout of exercise, Ex and C mice were inoculated intranasally with a standard dose (LD30) of HSV-1. Mice were monitored for 21 days for morbidity (time to sickness and symptom severity) and mortality. RESULTS: Ex females run time to fatigue was significantly longer than males (p = 0.027). No gender differences in susceptibility to infection were found in C groups. Ex was associated with increased morbidity in both male and female mice as indicated by time to sickness (p = 0.0046) and an increased symptom severity score (p = 0.042), but mortality, morbidity and symptom severity were not different between genders. Due to relatively small measurable changes, the sample size for these comparisons yielded relatively low power (0.5). CONCLUSION: Results indicate that 3 days of fatiguing exercise increases susceptibility to infection in both male and female mice. While no statistically significant gender differences were found in this experiment, further research with greater power is needed before firm conclusions can be made.