This study adds to our understanding of how exercise can help keep people fit and healthy as they age. In addition to the benefits of exercise already known – such as improved heart and lung health, lower cholesterol, better mental health, and stronger bones and muscles – exercise may also protect us from ageing at a cellular level. But there are limitations to what the study can tell us. The high dropout rate indicates that adopting an exercise regime that required 45 minutes of training, 3 times a week, isn't always easy.