macandbumble wrote:
I would say, go and do a squat with weight.
Where do you find it easiest, at the bottom of your squat, or at the top close to when you are back upright.
Extrapolate from there.....
That is probably not the best analogy, but I know what you are getting at. At the top of the squat, you already have the momentum from the bottom of the squat so it "feels easier" but you are not accelerating the weight from zero. F = mxa. At the top of the squat, the only acceleration is fighting the component of gravity. At the bottom, you're fighting gravity, plus adding acceleration to get the weight moving. I think we can agree that when the knee is at 90 degrees it is not in a biomechanically advantageous angle for applying force, but somewhere in between that and being locked at vertical is optimal (the 3/4 squat view of the world). Personally after using a powermeter, I dropped my saddle height by almost 2 cm and watched my power go up. Before I had a powermeter, the lower positions 'felt harder' and of course they were simply because my power was higher and i was doing more work. The higher positions felt easier because I was just riding at lower power (go figure).
If you looked at pictures of Jurgen Zack riding back in the day, while not the most aero position due to his back issues, if you looked at his leg extension he had a relatively low position compared to other peers.
I could drop my saddle another 1.5 cm and see no drop in power. It might affect other aspects of riding (aerodynamics since it will close my hip angle), but power will be fine. I have tried the experiment on gym bikes that have power and typically those stupid bikes have zero fore-aft adjust-ability and vertical adjustment is in increments of 3/4 of an inch...you just end up with a position that is too high or "too low". As an experiment given there is no aero penalty I have tried going 2 notches too low and seen zero impact on power output on the watts that those lifecycle machines show.