Physical exertion equals power. You can't have the same power with less physical exertion. It's a trade-off between aerobic capacity and anaerobic capacity.

Physical exertion equals power. You can't have the same power with less physical exertion. It's a trade-off between aerobic capacity and anaerobic capacity. You can pedal in a high gear, using more strength, or you can pedal faster in a lower gear, maintaining the same speed, but using more cardiovascular capacity. In both situations, if you are going the same speed, you are putting out the same amount of power. Non-circular gears change the gear ratio as you pedal. It effectively shifts down in that part of the pedal stroke where you have the least strength. Since the bike doesn't slow down, your feet must speed up. Then, when your feet swing around to where you have more strength, it effectively shifts up. My argument is, if you are pedaling at the limit of your strength, you are in too high a gear. Shift down and spin your feet faster. You'll use less strength, and more aerobic capacity, enabling you to maintain an equivalently high power output, but for longer. It's easier to run a marathon at a constant speed than to sprint 100 m at a time, taking walking breaks to maintain the same average speed.