Q. I weigh about 200 lbs and am 6 ft 3 inches tall. I am currently using a compact chain set 50/34 with a standard 25/12 cassette. When cycling with some (lighter) friends recently in the hills in the Dordogne there was a lot of chat about gearing etc. Because of my weight I was obviously having to use more power to maintain the same speed as my friends on the longer climbs of about 5 miles.
It got me thinking that if I could have gone to a lower gear and used a higher cadence I could have maintained the same speed and maybe used similar power to my lighter friends? Then the conversation went to crank length (mine is 175) and the whole think started to seem overly complex with too many theories and a cafe seemed the best idea! - B.
Can you gain an advantage by using a larger cassette (lower gear) and spinning faster?
Let's assume you measure your power output at the back hub. That tells you how much work you are doing (generally expressed in watts per minute). Training is the only way to increase your maximal total power output per minute. This includes interval training (which basically stresses your muscles to exert more watts per minute - and your body to recover from the anaerobic stress of doing so).
Assume you are exerting to your maximum - and producing your personal maximum watts per minute at the hub. You can deliver this power with multiple cadences. If your cadence is higher, the power per stroke is less, but total power per minute measured at the rear wheel is exactly the same as if you used a lower cadence with more power per stroke. You are not going to get "more power" by spinning faster.
The reason I encourage riders to spin at a faster cadence (90 - 100 rpm) is that there is less stress on your knee per revolution (remember, faster cadence = less power per revolution = less stress on the knee joint, than a slower cadence - assuming the same total power output per minute).
As far as I know, there are no short cuts. A good base, training at the length of the event you are aiming for, and intervals to force physiologic adaption and improvement are the components of a successful training program.