Jeff Woods is a professor of kinesiology and integrative immunology and behavior at Illinois whose research interests include the effects of exercise on the body's immune function. In an interview with News Bureau editor Melissa Mitchell, Woods discussed whether increasing levels of physical activity might be an effective means - in addition to other precautions such as vaccination and hand-washing - of reducing risk for contracting the H1N1 virus, commonly known as "swine flu."
Some of the investigations done in your lab with mice and humans in the past have suggested a correlation between various levels of exercise and immune function - especially in older people. What are the most significant findings to date?
In animal studies, we have found that moderate levels of exercise can reduce morbidity and mortality to experimental influenza infection, but severe, prolonged exercise actually increases morbidity and mortality. In our studies with older adults, we have demonstrated that 10 months of moderate cardiovascular exercise training (e.g. walking regularly) can extend the protective response to influenza vaccination such that it lasts throughout an entire flu season (October-April). This latter finding will soon be published in the Journal of the American Geriatrics Society. In addition, in another study published in the journal Brain, Behavior and Immunity, we demonstrated that this same training regimen improved the response to an experimental primary immunization in older adults.
Briefly, can you explain the results in terms of the biological/psychological processes taking place as a result of increased physical activity?
This really is the important question and, unfortunately, at this time I haven't an answer for it. One factor is that we really don't know why older people fail to respond as well as young people to vaccination. There are some clues that we are following up on in animal and future human studies. For example, we have reported that regular exercise can reduce elevated inflammation in the elderly - a factor associated with poor vaccination responses. In our study, we found that the exercise-induced improvements in influenza vaccine responses were not related to changes in cardiorespiratory fitness or improvements in psychosocial functioning so that rules out some potential mechanisms.
With indications that this particular strain of the influenza is already beginning to make people sick - long before the onset of the normal cold-and-flu season - is there still time for previously sedentary people to boost their immunity by beginning an exercise program now?
Yes. Available evidence indicates that people who are regularly active have reduced rates of upper respiratory tract infection. However, you need to be careful about not placing too much stress (physical or otherwise) on yourself especially given that this novel H1N1 is currently circulating. Starting a vigorous exercise program from scratch may not be warranted at this time. In addition, regular exercisers, especially ones that exercise in public places like gyms or fitness centers, need to be careful about exposure to H1N1 which is transmitted by sneezing, coughing and through contact with contaminated surfaces. All people, especially children, should get the swine flu vaccination and the regular influenza vaccination when available.