At the Australian Health and Medical Research Congress in Sydney last week Bouchard reported the results of a study assessing the role of genes in fitness and health changes in response to exercise. In the study, 742 people from 213 families were put through a strict 20-week endurance training programme. The volunteers had not taken regular physical activity for the previous six months. Exercise on stationary bikes was gradually increased so that by the last six weeks the volunteers were exercising for 50 minutes three times a week at 75 per cent of the maximum output they were capable of before the study. Previous reports indicated that there are huge variations in "trainability" between subjects. For example, the team found that training improved maximum oxygen consumption, a measure of a person's ability to perform work, by 17 per cent on average. But the most trainable volunteers gained over 40 per cent, and the least trainable showed no improvement at all. Similar patterns were seen with cardiac output, blood pressure, heart rate and other markers of fitness.
Bouchard reported that the impact of training on insulin sensitivity- a marker of risk for diabetes and heart disease- also varied. It improved in 58 per cent of the volunteers following exercise, but in 42 per cent it showed no improvement or, in a few cases, may have got worse. "It's negative, but it's true. Some people slog away and don't get any improvement," says Kathryn North of the Institute of Neuromu