About 10 years after he first started studying the causes of heart disease, Jerry Morris started to jog. “I was the first person to run on Hampstead Heath, in the 1960s," he'd later tell The Financial Times:
Every Sunday morning, if the weather was at all possible, I took off my coat, and my little boy carried my coat, I took off my jacket and my little girl carried my jacket, and I ran for 20 minutes. People thought I was bananas.”
Morris had discovered something, though, that those skeptics weren't yet aware of: People who exercised—routinely, vigorously—were less likely to have heart attacks than people who spent their days stationary.
From the beginning of his medical training, Morris had been interested in health inequities and their causes. In 1949, back in England after a stint in India as a lieutenant colonel, he turned his attention to coronary heart disease. The number of people whose hearts were giving out was rising like never before and no one knew why.
Morris had a hunch that it might have do to with the way people worked. Heart disease affected the middle-aged—more men than women—and statistics the government had collected hinted that occupation could play a role.
He started collecting data on 31,000 men, 35 to 64, who resembled each other in class and lifestyle, but differed in one key way: Though they all worked in the public transportation system, running buses, one group—the drivers—spent most of their days sitting. The other group—the conductors—spent their time trotting up and down stairs—500 to 750, every single day. (Morris' team had sat on the buses and counted.)