Originally Posted by
carleton
Yup.
Lance was known for (or rumored to be known for) targeting 120RPM when he would time trial and climb.
It's different for everyone. Basically, the faster you spin, the less time you have to add torque to each pedal stroke. Your muscles need a certain number of milliseconds to contract and add force. They also like to add force for a certain amount of time before they get exhausted...even between pedal strokes. When a muscle is contracting, it's not relaxed and "refueling".
If the cadence is too low, you are calling on the muscle to contract for longer than optimum. When the cadence is too high, the stroke is over before the muscle can do as much as it could. There is a sweet spot.
Distance runners have a sweet spot as well. Studies have shown that pro distance runners manage to hit the same cadence no matter their gender, height, or stride length. That cadence is around 180 steps per minute.
In contrast my cadence on time trials is completely variant from road races. In a typical road race my cadence will be on average of 100rpm, then higher on sprints and break-aways. There is a strategic reason for that, which I won't go into here. For time trial efforts, my ideal cadence is between 85 and 90rpm, preferably toward 80rpm. This is because at higher cadences in threshold zone, my heart reaches lactic acid threshold rate before my legs reach power threshold, which is not good because I could be at threshold power but lower end of heart rate VO2max and not be able to sustain a 40K effort. So by backing down my cadence I can maintain higher levels of power/torque with a relatively lower hear rate. It's just how my own physiology works and how it has tested out for me. That may change with track racing, which is starting to condition me to ride with higher cadences. It will be interesting to see how my system adapts.