Moderate physical activity in old age appears to invigorate the mind as well as the body. B. M. van Gelder of the National Institute for Public Health and the Environment in the Netherlands and his colleagues have found that elderly men who partake in moderately intense activities stay sharper than their less energetic counterparts.

In one of the few studies to assess physical activity and cognition over a long period, the researchers began in 1990 to track the exercise habits and mental abilities of 295 men ages 70 to 90. The subjects were monitored for an entire decade. Members of the lowest-intensity group, whose pursuits included playing billiards or walking at a pace less than three miles per hour, showed a cognitive decline that was up to 3.5 times greater than that of men who played volleyball or walked at three miles per hour (called the medium-low-intensity group). And yet men in the medium- and high-intensity categories (those who engaged in gymnastics or swimming, respectively) did about the same as the medium-low-intensity set, indicating that seniors can stave off some decline with just moderate exercise.

As for how exercise benefits mental capabilities, van Gelder's group speculates that it may be the result of better cardiovascular fitness, which boosts cerebral blood flow. Or the physical activity may stimulate brain cells in the hippocampus, the center of long-term memory.