The Authors' reply In the interim since our editorial was published,1 the Copenhagen City Heart Study focusing on longevity in joggers, has been published in a prestigious peer-reviewed journal.2 This large prospective longitudinal observational study followed 1878 joggers and 10 158 non-joggers for up to 35 years. They found that joggers, as compared with the non-joggers, had a remarkable 44% lower risk of mortality during follow-up for both men and women. The age-adjusted increase in survival was about 6 years in both genders. However, U-shaped curves were apparent for mortality with respect to quantity of jogging (figure 1), estimated running speed (figure 2), and frequency of jogging (figure 3). These curves suggest that the benefits of jogging are most robust for those who jog between 1 and 2.5 h per week, at a slow to moderate pace, at a frequency of about 2 or 3 times per week. In those joggers who were doing a higher volume, higher-intensity running, the long-term mortality rates were not significantly different from non-joggers. In other words, overdoing the running substantially diminishes the remarkable gains in longevity conferred by moderate jogging.