i recently noticed that my toes tend to point downward as i pedal - particularly at the 'low' point of the stroke. which part of my set up would be responsible for this (if any)? is it just a bad habit, or something that could/should be remedied? my seat, as far as i can tell, is at the right height, ie: as i sit on the bike, my leg extends fully at the lowest point, without over extending or 'locking' at the knee. anything else i should look at?