HISTORY OF THE BICYCLE PART 2 (Anatomy of the Pedal Stroke)

No, Part 1 has not been posted yet. First off, let me preface this post by saying I am by no means any kind of expert. I have read and ridden enough to form an opinion. Second, if any of you have input, please post a comment.

I was down at my LBS (Sharp Bicycles) when another regular came in from a test ride. He was trying out a bicycle set up for time trials. When asked how he liked it he said he wasn’t sure about the forward position, “it felt a lot different.” The conversation turned to the angles and position on TT bikes. I did my best to explain to him about pedal stroke, leverage, and momentum. Here is a better explanation:

Since the introduction of the drive train to the bicycle, people have been pushing pedals. The average person thinks of the pedal stroke as just that, pushing down on the pedals and the way that the average bike is setup, this is true. The more advanced cyclist will either strap in with cages or step into a clipless pedal. This allows you to apply force to the crank arms at any angle. This results in more power to the drive train, more muscle groups engaged, and more efficient use of your energy. Think of moving your feet in a circular motion. I tell my spinning students to pedal the full circle by pushing forward, pushing down, pulling back (like scraping mud off the bottom of your shoe) and pulling up. What ever one leg is doing, the other is doing the exact opposite. There should be no dead spots in your pedal stroke.

Road bikes have your hips positioned behind the bottom bracket, hence the crank arms. This is so you have leverage pushing forward and pulling back, especially in a seated climb. If your hips are too far forward, you lose this leverage and thus the extra power and efficiency. Most road races and rides involve climbing. The geometry of the seat tube and position of the saddle help optimize the hips back position which makes you a more powerful and efficient rider. Notice (in the illustration to the left) how the heel drops when starting the forward motion through the beginning of the down stroke.

Time trials are usually relatively flat courses without too many turns or hills. TT bikes are designed to be more aerodynamic. In this position you’re leaning forward in the aero bars. This puts you out of position to use any leverage pushing forward or pulling back. So for aerodynamic and efficiency the geometry of TT bikes position your hips forward over the cranks. This is a more comfortable position while in the aero bars and a more efficient position to maintain forward momentum with an up and down pedal stroke. This is a diagram of the proper pedal stroke on a TT bike. Notice the up and down use of the heel. You want to apply as much constant force to the cranks as you can.

There are other considerations like form, saddle and cleat position that help transfer the most power to the cranks. Apply all these elements and those pistons that are your legs will make your bicycle scream up or down the road.

Once again this is my opinion based on what I have read and what works for me. Practice these techniques and you will see a difference in your speed and endurance. Todd, I hope this helps.