pedaling on level ground is analgous to dribbling a basket ball. most of the work is used for the downstroke and a toeclip or clipless pedal in this instance is helpful for keeping you foot in place, thats it. however climbing, especially standing efforts are when they come into play. the instep (top part of foot) needs to be strapped down in some way, otherwise you end up sliding forward and loading your knee and tibia muscles in weird ways. in fact you shouldn't be doing much standing riding anyway, but thats another story....