Jack Stapleton has three hobbies in Contagion: running, bicycling, basketball playing. Starting with biking, he cycles to work at the Office of the Medical Examiner every morning down what he calls a "slalom" (long and twisting hazardous stretch going in and out as in a ski slalom). He also cycles to other destinations during the day, particularly, during the chronology of Contagion, to Manhattan General hospital where he invariably gets himself into trouble.
Jack's daily route included a hair-raising slalom down Second Avenue from Fifty Ninth Street to Thirtieth Street at breakneck speed. There were frequent close calls with trucks and taxicabs and the inevitable argument.
He also goes running through Central Park. During Contagion, after Twin allows his bike to be taken by Reginald as part of their price for delivering a warning to Jack about staying away from Manhattan General. Jack also runs home from work having taken the smelly subway to work in the morning. It is also while running in Central Park that Jack has to outpace an assassin's bullet.
Reginald ... couldn't believe his luck ... chasing his prey into the dark, deserted [Central] park was making the job almost too easy.
His third hobby is basketball playing, which he does as often as possible at the neighboring court where the local black gang plays under the authority of Warren. To play basketball with this neighborhood gang, Jack has to learn the subtleties of negotiating communication and protocol on the basketball court. It is this effort on his part and the companionship of the basketball court that wins Jack his friendship with these young men that take him into their guardianship and save his life.
It's important to note that while Jack has three simple hobbies, Cook has made each of the hobbies integral to character development and plot development.