No definitive answer exists to the question of whether or not a bicyclist's leg should extend fully when pedaling. Different cyclists adopt different techniques, and there is no one correct way to pedal. That said, many experienced cyclists believe that it is better to keep the leg slightly bent at the knee when pedaling, as this allows for a more powerful stroke. It is also important to maintain good form and avoid rocking side-to-side while pedaling, as this can lead to reduced efficiency and even fatigue. Ultimately, it is up to each individual cyclist to experiment with different techniques and find what works best for them.