The Body: A Guide for Occupants

by Bill Bryson

For the longest time, the crucial importance to health of just moving around was hardly appreciated. But in the late 1940s a doctor at Britain’s Medical Research Council, Jeremy Morris, became convinced that the increasing occurrence of heart attacks and coronary disease was related to levels of activity, and not just to age or chronic stress, as was almost universally thought at the time. Because Britain was still recovering from the war, research funding was tight, so Morris had to think of a low-cost way to conduct an effective large-scale study. While traveling to work one day, it occurred to him that every double-decker bus in London was a perfect laboratory for his purposes because each had a driver who spent his entire working life sitting and a conductor who was on his feet constantly. In addition to moving about laterally, conductors climbed an average of six hundred steps per shift. Morris could hardly have invented two more ideal groups to compare. He followed thirty-five thousand drivers and conductors for two years and found that after he adjusted for all other variables, the drivers—no matter how healthy—were twice as likely to have a heart attack as the conductors. It was the first time that anyone had demonstrated a direct and measurable link between exercise and health.