Jeffrey A. Woods, PhD, and graduate student Tom Lowder at the Physical Fitness Laboratory, Department of Kinesiology,
We had completed a lot of in vitro studies, but we wanted to study now how exercise affected animals against a real infectious challenge, Woods said. The question they addressed in their study, Protective effect of exercise on mortality due to influenza in mice, was can exercise protect against morbidity and mortality? While exercise protected mice from mortality, it didnt seem to have any affect on gross measures of sickness behavior like food intake and cage activity.
Daily Exercise Until Symptoms Are Present
Male mice 11 weeks old to 20 weeks old were infected with influenza virus and then randomly assigned to exercise (EX) or home cage control (HCC). The EX mice were exercised for 20 to 30 minutes for four days and multiple subjective and standard measurements were recorded.
The animals did very moderate exercise while they were mounting an immune response, Woods noted. As soon as symptoms appeared, exercise was stopped, to mirror how most people react once they come down with flu-like symptoms. The mice were naïve, that is, they previously hadnt been exercising on a regular basis.
Results Both Striking and Surprising; Human Flu Vaccine Reaction Study Underway
20-week-old mice that had exercised had significantly (p=0.008) higher survival rates (18 of 22) versus HCC of the same age (10 of 22). However, 11-week to 16-week-old mice didnt show a significantly higher survival rate. When all EX mice (47) were compared with all HCC mice (48), EX had twice the survival rate, 59 percent vs. 29.4 percent (p=0.003). None of the variables (food/water intake, random activity or symptom severity) proved to be reliable at predicting mortality. However, severe lethargy was apparent one to two days prior to death. And while there was a marked, age-dependent effect on mortality, there was no effect at all on morbidity, which was somewhat surprising, Woods said.
At the moment, the laboratory also has a large NIH-funded human clinical trial underway examining whether or not moderate exercise training can improve immunological vigor -- including responses to influenza vaccine -- in older adults.
Source: American Physiological Society