Originally Posted by
terrymorse
This "pull up" vs. "don't pull up" on the pedals discussion is somewhat of a simplification. In reality, there is plenty of pushing and pulling in different directions throughout the pedal cycle.
Different muscles are engaging throughout the pedal cycle to make the pedals go in circles, pushing forward on the pedals near the top, pushing down and forward in the first quadrant (0º-90º), pulling back in the next two quadrants (140º-270º), pulling up in the last quadrant (270º-360º).
Here is what the quadriceps and hamstrings are doing throughout the pedal cycle. I've marked the graphs with what the muscles are doing, either flexion (bending) or extension (straightening) a joint.
Roughly, the hamstrings extend (straighten) the hip joint on the down stroke (pushing down on pedals), flex (bend) the knee around the bottom of the stroke (pulling back on pedals).
Also roughly, the quads extend (straighten) the knee on the down stroke (pushing forward on pedals), flex (bend) the hip on the up stroke (pulling up on pedals).
The charts below on the left is crank force data from competitive and recreational road cyclists. If these cyclists are recruiting their muscles in similar manner to your charts, then they're wasting a significant amount of effort from around 180 to 360 degrees of the crank angle. You'll see the pull up force they make on the upstroke is very little to matter at all and they can only pull the pedals up at low cadence (60 rpm) which is not really an efficient cadence especially for long distance riding.
The colored chart on the right is how I recruit my muscles in the full rotation of the crank (this is perceived effort, not actual force on the crank). Note, I actively recruit the glutes too to avoid overworking the quads and the knees. Link to the left charts:
https://www.researchgate.net/publica...during_cycling
