Originally Posted by aaronmcd

Assuming only downward force, top to bottom (or down + up as a couple producing max torque at horizontal cranks):
work (Joules, one stroke) = F*distance = F*2L (L = crank length in meters)
work (Joules, one minute) = 2C*F*2L (C = cadence in rpm, so 2C = strokes per minute)
power P (watts) = work/time = 4CFL/60
F = 15*P/(C*L)
F (lbs) = 0.22481*F (Newtons)
F(lbs) = 3.372*P/(C*L)

If L = 172.5 mm
P = 300 watts
C = 60 rpm
F = 98 lbs

So if you weigh 150 lbs, you can generate 450 watts just by stomping all your weight on the pedals