On a racing bike, every bit of energy put through the pedals should go to the drivetrain. Therefore, having the right shoes is crucial. Ambitious road cyclists rely on "clipless" pedals and their accompanying shoes, meaning the shoe clicks firmly onto the pedal. A stiff sole then transfers energy through the shoe to the pedal, allowing the rider to transfer energy on both the downstroke and when pulling up. In contrast to mtb shoes, road shoes use larger 3-bolt cleats and have flatter soles. While this makes walking difficult, it equals a lighter, more aerodynamic profile.