Stronger Brains (01.22.04) - Are you having trouble keeping that New Year's resolution to get more exercise? Scientists are finding more reasons you should stick to it. Memory and Exercise (11.20.03) - Does too much exercise hinder learning and memory? Is Exercise Brain Food? Depression and Exercise Use it or lose it. When it comes to exercise, that's how we stay fit. But, as this ScienCentral News video explains, genetics may control who will be able to stay most active. Exercise Better for Some Exercise is the road to fitness but for many it's an up hill battle. Gerontologist Stephen Kritchevsky says differences in our genes may explain why some of us reap the benefits of exercise more than others — especially as we age. This may offer new opportunities to explore treatments to help older adults maintain their mobility. "Even if you exercise, it doesn't guarantee that you will maintain function," says Kritchevsky, from Wake Forest University Baptist Medical Center . "There are other things going on." As part of much larger study to investigate the functional health of older people, called the Health ABC Study , Kritchevsky and his research team followed the health and activity levels of more than 3,000 people in their 70's over four years. "We asked them what kinds of physical activity they did over the past two weeks and took a blood sample to find out kind of what genotype that they had," he explains. "And then we talked to this group every six months over the next four years." Regular exercise helped most of them gain or maintain their mobility. Kritchevsky says, "People who were physically active when we first talked with them maintained maintain walking ability much better than the people who weren't physically active." However, a small percentage developed mobility problems in spite of exercising. It turned out they had a variation in a gene called ACE (angiotensin converting enzyme) , what the researchers refer to as a difference in the person's genetic make-up, or genotype . One of three genotypes of the gene, II genotype, is linked to extra leg muscle fat. "The people with the II genotype tended to have a greater level of body fat, fat in the leg muscles themselves," Kritchevsky says. "We know from Health ABC and other studies that the amount of fat that is in and around the muscles is a very strong determinant of how well the legs function, both in terms of strength and endurance." Until now what science knows about the II genotype comes primarily from work with highly-trained athletes. "Among very active and highly trained athletes, it appears that the II genotype is actually associated with superior endurance function. So among marathon runners, for example, there seems to be a predominance of people with the II genotype. One thing that has recently come to be understood is that marathon runners and highly trained endurance athletes actually have a fair amount of fat in their muscle cells. So if you are an endurance athlete, having this ready sort of energy could be very important. In less well-trained older people, having a lot of fat can be actually be a negative thing," he explains. Kritchevsky says that's because the fat could be impairing muscle function. But he believes that other genes are likely at work, as well as environmental factors, since not all people with this gene variation has trouble staying on the move. "So even if you exercise, or even if you don't exercise, it doesn't mean for absolute certain that you are going to have decline in mobility function," he says. For now, he says there's no reason to be tested for the gene, but exercise plans based on DNA may be in our future. "Maybe we will be able to tailor customized exercises for the genotype that you are, but I think that is many years in the future." Genetics aside, Kritchevsky stresses that exercisers still stay healthier than couch potatoes. "Older Americans should try to maintain a high level of physical activity as they move into old age," he says. About ninety minutes a week of walking, weights, dancing or biking is recommended

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