but if you're a person who works out and wants to stay fit, biking is more efficient because you build muscle and endurance and at the same time get from point A to B, instead of just working out inside a gym, where the air isn't as healthy (unless you live in a big city where there is loads of smog, which wouldn't be as big a problem if the majority rode bikes where they need to go, taking up less space and creating a healthier population).