I received a number of questions re leg strength and pedaling imbalance. There are many good reasons to strength train but addressing the query of “Doesn’t pushing harder require more force and therefore stronger legs?”
It’s important to understand on-bike power which is computed as Force x meters-per-second = Watts. Many cyclists fail to fully understand the computations required to make sense of this.
Meters-per-second is best understood by using your crank length (for instance 175mm) and multiplying it by 2 to obtain a diameter of 350mm and then multiplying that by Pi (3.14) to obtain circumference of the pedal arc. Multiplying Pi by .350 results in 1.099 meters for one crank rotation and then assuming 90rpm, we multiply 1.099 by 90 yielding 98.91 meters for 60sec. and then we divide that by 60 to obtain 1.6485 meters-per-second when pedaling @90rpm with 175mm cranks.
Having that figure we then divide our desired wattage (assume 300W) by 1.6485 and we have a required force of 182 Newtons. There are 3.60 ounces per Newton so multiplying 182 by 3.6 yields 655 ounces which we divide by 16 (16 ounces per pound) to obtain a requisite pedal force of 41 lbs. and that is evenly all of the way around the pedal arc which of course no one can do because pedaling results in more force at certain points of the arc and less at others.
However, that isn’t a lot of force although one likely must pedal near double that force (accounting for dead-spots and self-resistance in the stroke) through the power phase on each side of the stroke but even that is still only 82lbs. – still not a great deal of force and even less if on raises rpm — but the challenge becomes in maintaining that for thousands of revolutions.
So, my point on strength training is that a strong core providing a stable platform good leg alignment to sustainably push from is much more important than having the ability to push very hard for brief periods.
Bill Black