He's his own person and he's in charge of his training, his race results, and his life. You can't make him train; he has to make himself train, and it has to be because it's important to him. Unfortunately, you're the one who has to live with his attitude. Actually, you don't have to put up with it. You could tell him that he can belly ache and complain only when he's put in the kind of training you've been doing.