The adventures of Paul, Black and Breinan offer a glimpse into a forgotten aspect of the running boom of the late 1970s. Preternaturally self-disciplined, they were among about 75 children (ages 8 to 13) who tackled the early years of the New York City Marathon in a time of novelty and naïveté. Organizers were uneasy about young runners, but it was not until 1981, records show, that age 16 became the requirement. New York’s official minimum age became 18 in 1988, after an advisory set by the International Marathon Medical Directors Association in the early 1980s, and reasserted in 2001. With no conclusive study, physicians still debate risks to children who compete in marathons, like muscular-skeletal injuries, stunted growth, burnout, parental pressures and the ability to handle heat stress.