The Sunday Morning Post: Why Exercise Is a Miracle Drug
Welcome back to The Sunday Morning Post, this newsletter’s weekly rundown of the most interesting and important stuff I’m seeing in science, technology, economics, and beyond. Comments are open. Leave tips, papers, studies, tweets, posts, questions, and graphs in the comments, if you think they’ll serve for future editions.
Euan Ashley has claimed that exercise is the “single most potent medical invention” ever—more broadly effective than any medicine discovered in the natural world or devised in a laboratory. In 2025, this is the sort of rah-rah sentiment about working out that one might associate with a Make America Healthy Again ambassador rather than, say, the chair of medicine at Stanford University. So, what makes Ashley’s claim significant is that he is the chair of medicine at Stanford University.
Last year, Ashley and a large team of scientists conducted an elaborate experiment on the effects of exercise on the mammalian body. In one test, Ashley put rats on tiny treadmills, worked them out for weeks, and cut into them to investigate how their organs and vessels responded to the workout compared to a control group of more sedentary rodents. 1 The results were spectacular. Exercise transformed just about every tissue and molecular system that Ashley and his co-authors studied—not just the muscles and heart, but also the liver, adrenal glands, fat, and immune system.
