Only the smart guys work out. And the guys who really want to win will work out harder, and watch what they eat. You can cross-train also. You have to keep your attention and perceptions ( depth, speed, distance, hearing) in constant sharp focus. And even be able to improve them and learn new tricks. Riding dirt bikes, snowmobiles, racing mountain bikes, etc. will make you more indepth to the feel of the physics that are involved with motorsports, and with racing on different terrains. Even flying an airplane or racing boat can improve you reflexes and attention. And last but not least. They still have to drive their cars in test sessions. But yeah, they workout. But they have fun doing it!