As the skater pushes off with his rear leg, a perpendicular force F is exerted on the skate by the ice. The component of the force F that points forward (in the direction of motion) is what pushes the skater forward. At the same time, his other skate is either raised or gliding on the ice. As the skater moves forward he then switches to the other leg and pushes off the ice with that one, and the process is mirrored. To push off the ice with greater forward force (and accelerate faster), the skater increases the angle α, which increases the component of force in the direction of motion.
A skater can also skate backwards using a gliding pattern in the shape of a lazy "S" (as shown below), in which the skater's blades never leave the ice. However, the skater cannot push off against the ice as hard as he does when skating forward, which means he cannot go as fast. In this technique, the skater pushes against the ice with his push-skate facing inward, while his other skate glides. As the skater moves backwards he then switches to the other leg and pushes off the ice with that one, and the process is mirrored. Thus, the physics of skating backward is similar to the physics of skating forward.