A study has found that cycling can hold back the effects of aging and rejuvenate the immune system. Scientists conducted tests on 125 amateur cyclists aged 55 to 79 and compared them with healthy adults from a wide age range who did not exercise regularly. The findings, outlined in two papers in the journal Aging Cell, showed that the cyclists preserved muscle mass and strength with age while maintaining stable levels of body fat and cholesterol. In men, testosterone levels remained high. More surprisingly, the anti-aging effects of cycling appeared to extend to the immune system. An organ called the thymus, which makes immune cells called T-cells, normally starts to shrink from the age of 20. But the thymuses of older cyclists were found to be generating as many T-cells as those of young people. Prof Janet Lord, director of the Institute of Inflammation and Ag ing at the University of Birmingham, said: “Hippocrates in 400 BC said that exercise is man’s best medicine, but ...