It is not often that someone comes along who is a good friend, a good writer, and a good doctor. Donahue, the author of Germs Make Me Sick (1975), appears to be all three. Drawing frequently on his own experience as a pediatrician and team doctor for his home town (Hartford, Wis.) high school, Donahue writes sensibly, informally, and uncondescendingly on ""getting the best out of your body"" and on a variety of irritants and injuries from shin splints, jock itch, and joggers' knee to skull fractures and ruptured spleens--always explaining the physiology behind the problem and why the doctor will probably take a certain course of action. Donahue delivers tough lectures on drugs and on playing while sick, and he warns against heat exhaustion and dehydration, false remedies, and running near air-polluting highways. He seems to cover about everything a young athlete might wonder about, and Mimi Harrison's cartoons give the handbook an approachable look.