According to this book http://www.amazon.com/gp/product/B00...w_myk_ro_title, higher cadences of 90-100 use more slow twitch muscles, which fatigue more slowly than fast and intermediate twitch muscles. The downside is that there is a higher aerobic demand. The theory is that the faster cadence pushes more blood to the heart and then more oxygen-rich blood is pumped to the body for increased aerobic performance. This reduces anerobic activity and lactic acid creation, which have limited energy stores and (and alot more pain).