( study subject to identify which version...)Exercise aside, genes may ultimately dictate seniors' mobility

Study participants were categorized according to their exercise intensity and their genetic makeup. Overall, about 41 percent of study participants became less mobile over the four-year period. Even though people who exercised were less likely to develop substantial physical limitations, not everyone received the same benefits, even if they exercised with the same intensity.

About a third of the seniors engaged in significant physical exercise including walking and strenuous exercise, and they preserved their mobility longer than the 70 percent who engaged in little or no physical activity. Researchers also evaluated the 8 percent who reported participating in weight training.

But genetic makeup influenced long-term physical function. Among exercisers, the DD and ID genotypes were more likely to remain fit than those with the II genotype, who developed mobility problems at a 45 percent higher rate, researchers found. No difference in mobility according to genotype was found among non-exercisers, suggesting function was influenced by an interaction between exercise intensity and genetic make-up.

In addition, seniors who reported weight training and had the DD or ID genotype displayed the lowest rate of mobility loss in any exercise category. In contrast, weight trainers with the II genotype developed physical limitations similar to those experienced by seniors who were relatively inactive.

What differences in body composition the genotype creates also may yield clues to what causes mobility limitations to develop with age, and what people can do to stay active, Pahor said. Those with the II genotype, for example, tended to have higher total body fat.