Originally Posted by bboseley
I always seem to be confused about some aspect of cycling. Now is no exception. I have recently moved my seat position fairly far back at the insistence of what we can call my coach. Former racer, LBS owner, etc. Sure enough, my pedaling power increased, along with speeds, and virtually no hand, arm, or shoulder issues. Feels great. Now my confusion comes from whether I am using primarily quads or glutes in this position – and more importantly – what difference does it make which I am using? Also, from this back position, should I be using heals down or toes down as I come over the top? I will sleep much better if I eliminate the current confusion.
When in doubt, heels down (at least when sitting). This allows the knee to straighten a few degrees more than it does with the toes down and gives you better leverage. It's a little harder to spin this way, but when you need the extra power to get up a hill, it helps.
Sliding back on the seat does two things: it extends your legs further, giving you better leverage, and it forces you to lean forward a bit more. This helps get your glutes more involved in your pedal stroke.