We all know that exercise is good for us, but many of us do not get as much physical activity as we would like. A new study conducted by researchers from Iowa State University at Ames has found that this flu season may be a good time to start. The study found that a single workout could as much as double the body's protection against the flu.

Scientists and doctors agree that the single best way to protect oneself against the flu is to receive a flu shot. However, the flu shot's efficacy against infection can range from 50 to 70 percent, depending on the amount of antibodies that it causes a person to produce. In general, the more antibodies a body produces the more protection that person has against influenza. Because some people's bodies naturally produce more antibodies than others, researchers wondered whether people could do more to boost their immunity protection.

Indeed, they found that it is possible. They conducted an experiment in which participants, most of them college students, received a flu shot. Afterwards, some quietly sat for 90 minutes. Other participants set out on a 90-minute jog or bike ride 15 minutes after inoculation. A month later, when the researchers tested the participants for antibodies, they found that the groups who had exercised afterward had nearly "double the antibody response".

In order to test exactly how much exercise was required, researchers conducted a study with mice. All of the mice received a flu shot. Then, a third of the mice exercised for 45 minutes, a third of the mice exercised for 90 minutes, and a third exercised for three hours. They found that the mice who exercised for 90 minutes had the most antibody protection. Interestingly, it appeared that mice that exercised for three hours had lowered the immune response with too much exercise, while the 45-minute group had not gotten enough exercise. It appears that 90 minutes is the sweet spot.

However, for those of us unable to squeeze in a 90-minute trip to the gym, a 2007 study published in the journal Brain, Behavior and Immunity suggests that the work-out routine can be different for people who exercise before receiving the flu shot. The participants lifted weights, which weighed 85 percent of the maximum weight that they could lift once, for 20 minutes before they received the flu shot. Those who exercised before the shot had a higher antibody response than those who did not, though the effect was muted among men who had a higher antibody response to begin with.

The reasons that exercise appears to boost the effects of a flu shot are varied. In the case of the 2007 study, researchers believe that the workout created inflammation in the arms, which increased immune response. The researchers behind the 90-minute workout study say that they think that exercise helps pump the vaccine throughout the body and helped the entire body's immune system.

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