Not only did Maniac win the race against Mars Bar, but he also won it running backwards. Maniac is glad he won, but he feels bad about humiliating his opponent in the process, and wonders what it is within himself that possessed him to do that.
Maniac didn't want to race Mars Bar to begin with. The other boy has always been belligerent towards him because he is white, and he only wants to race Maniac because he wants to show him up. Mars Bar thinks he can beat Maniac because has been working out, and has gotten a fantastic new pair of sneakers. There are a lot of people watching the contest, friends and neighbors of Mars Bar, so there is a lot at stake.
Maniac is not sure at first how to run the race.
"Naturally he wanted to win, or at least to do his best...but there were other considerations...whom he was racing against, and where, and what the consequences might be if he won".
Maniac doesn't want to make Mars Bar look bad, but he doesn't want to be beaten either. Once the race begins, however, he is caught up in the excitement, and, leading all the way, he turns at the last minute and crosses the finish line backwards. Maniac "regret(s) it instantly", questioning himself as to why he did it. He is afraid that he might have done it deliberately, disgracing his opponent as a form of payback "for all his nastiness". In the final analysis, however, "his only recollection (is) a feeling of sheer, joyful exuberance, himself in celebration", doing what he does well with complete abandon (Chapter 38).