Want to get older slower? Run faster, or at least more often. Researchers at the University of Birmingham, U.K. are convinced that people who exercise regularly maintain more muscle mass and have immune systems that appears to have aged slower than the immune systems of people who do not exercise. A U of Birmingham news release reports that researchers recruited 125 amateur cyclists aged 55 to 79, 84 of whom were male and 41 were female. The men had to be able to cycle 100 km in under 6.5 hours, while the women had to be able to cycle 60 km in 5.5 hours. When their lab tests were compared to those from a group of adults who don’t exercise, the researchers found far less loss of muscle mass and strength in those who exercise regularly. The cyclists also did not increase their body fat or cholesterol levels with age and the men’s testosterone levels also remained high, suggesting that they may have avoided most of the male menopause. Wait, there’s more: the cyclists were found to have an immune system that did not seem to have aged either. The cyclists’ thymuses were making as many T cells as those of a young person.