- May 31, 2004
Fday said:I didn't know that the efficiency of contracting the quads varied depending upon where the foot is on the pedal circle.
I'm not sure what you mean Fday, but I know that cycling by contracting my quads while on the upstroke and contracting my hamstrings on the downstroke would lead to much going nowhere very quickly. (Ok, maybe the glutes could get me to move forward).
My take on the attempt to tangentially direct the force using the quads. The problem is that you need to start the contraction earlier in the crank cycle (just as the foot comes over the top or before) to have any benefit (the torque of sideways leg force is maximized here). That benefit comes at a cost of having to have the quads active for a longer period of time (as WarrenG already said) if one wants to apply force during the rest of the downstroke. There's another drawback, in that the mechanical advantage of the quads (and hams and glutes) action is better when the leg is more extended. To me that means quad action should be reserved for the last half of the downstroke, not the first half.
I also know intuitively that leg and hip extension is enhanced by simultaneous action of all muscle groups. Having one fire here (quads), and another there (glutes) isn't the best way to develop power, slowly (road racing) or quickly (sprinting). That's for one half of the pedal cycle.