From: http://joomla.bonzerwork.com.au/inde...=69&Itemid=105




Fig 3: pedal angle and timing of torque: The orientation of the pedal and the resultant force vector are shown at 20 positions of the crank cycle. It is interesting to note the orientation of the force vector during the first half of the revolution and the absence of pull up forces in the second half.


I think this same result has been found in other studies as well. On normal bike cranks, nobody is really pulling up enough to generate an upwards force on the "backstroke" of the pedaling motion; you are just lessening the amount you are pushing down, and that's why people call it "unweighting" the upwards traveling leg/foot. The force diagram shows that the foot is still pushing downwards on the backstroke... This is not to say that single leg pedaling drills are not worthwhile either...