Complex sentence: Klitschko is the only heavyweight world champion to have never been knocked down in any fight, and alongside George Foreman he is the only heavyweight boxer in history to defend a world title after turning 40.
Split into simpler sentences: Klitschko is the only heavyweight world champion to have never been knocked down in any fight. Alongside George Foreman he is the only heavyweight boxer in history to defend a world title after turning 40.