Over the last few decades, evidence on the beneficial effects of physical activity on health has been accumulating, and public health awareness has increased about the tangible benefits of promoting active habits among the general population.^1,2 In Nebraska (USA), investment in cycling and pedestrian trail paths has been offset by the direct health benefits alone.³ Studies on physical activity have focused more and more on dose-response effects⁴ and specific effects of different types of training,⁵ and also on the effects of detraining⁶ and side effects of exercise, which seem to be minimal but may occur if …