Tuesday, January 02, 2007

Sprinting - Tilting your bike (goes for climbing too)

This is from cyclingforums.com (which I posted). It's been cleaned up a bit for the blog.

As a rider with shorter legs who loves sprinting (say, like Abdujaporov), i.e. not like Cipo or Boonen or those tall guys, I always wondered why Abdu got such a raw deal on "throwing his bike around". I thought he rocked his bike a normal amount.

I *don't* have any scientific proof to back this up but this is my theory:

1. A rider can exert more force downward with their legs than their total body weight. I just saw a clip on YouTube of a guy doing 2300 lbs on the leg sled thing - eight times. He's a big guy but way less than 2300 lbs (he also squated 800 lbs, watching the bar flex like a wet noodle was incredible)
2. In order to exert more downward force than your body weight, you need to pull up on the corresponding side of the handlebar. For example, to push down on the right pedal with, say, 300 lbs of force, you need to pull up with 300-(your body weight) amount of force.
3. The most efficient way to exert that amount of force is to lift straight up. If you lift at an angle, you have to do more work to get the resultant "X" lbs of upwards force.
4. In order to make the lift angle perpendicular, the rider needs to move the part of the handlebar where it is being held to the same vertical plane as the pedal.
5. Since the pedal is anywhere from 7-10 cm off of center and the bar is anywhere from 20-23 cm off center, the bars need to be moved "inward", i.e. closer to center.
6. To move the bars inward, you can lift or drop the bar. Lifting the bar is easier since you're already exerting a lifting motion. If you drop the bar, your downward pedaling force will exacerbate your bike flopping onto its side.
7. Depending on your bar to pedal height difference, it will require a different amount of tilt to line the bar up with the pedal. A shorter frame will be tilted much more, a taller frame not as much, even taking into account wider bars on the taller frame.

This last thing is why I don't think Abdu was tilting his bike excessively. He was tilting his (very small) bike enough to line up his drops and his pedals, relatively speaking. Okay, he ran into that Coke Can in Paris, but Wilfred Nelison ran into the cop and no one pointed that out if the cop wasn't there, the Belgian would have hit the barriers sticking out about 5-10 feet past the cop.

Some heretical evidence (kind of like Christopher Columbus noting that the masts of ships drop down, not shrink into the distance - no proof per se but he thought the world was round based on that.... or was that more elementary school propaganda?) - when you get out of the saddle on the trainer, you move your upper body side to side.

Well I should say that *I* do this. I theorize that I do this is to get my weight over the pedal. To paraphrase a particular saying, "If the pedal can't come to me, I'll go to the pedal." On the road I don't move my body over like that too much unless I'm goofing off, pedaling really slowly, or totally blown. This is also a typical thing to see on the road, even in the saddle - the "rolling shoulders" thing that points out when a rider is vulnerable to attack. The rider is simply moving more of their weight to the downstroke side of the bike. This lets them put a slight bit more pressure downwards without too much upper body work.

Again, no scientific proof (watts or pounds or whatever) but after a lot of racing, a lot of sprinting, watching a lot of tapes, and studying optimizing sprinting for a very long time, this is what I think is happening.

1 comment:

GMF said...

I like this topic. More sprinting posts, Aki.
Not only did Abdu's bike sway side to side, the wheel turned and flopped somewhat as he pedaled. Seemed like he effectively did a mini slalom type of deal as he sprints out of saddle. Old riding buddy of mine Mike and I used to play "Guess The Pro" by imitating the idiosyncratic riding styles of various riders. I always did Abdu and the slalom wheel thing and he did Zabel: very up and down stiff upper body pushing straight down on the pedals like pistons in a car engine, his head bobbing up and down with his legs. I think Adbu used more of each pedal revolution with his more body motion while Zabel seemed limited to "muscling" the pedals more straight down by being more rigid. Robbie McEwen is a current smaller rider that seems more like Abdu. He also tends to be able to be more nimble moving around in the field during the sprint to find a way to the front whereas a Zabel or Cipollini power sprinter was more like a diesel truck straight to the finish line.
As for my style, someone once taught me to first hold the drops (non-anatomic of course) in the deep part of the curve before the flats and rotate my wrists out so that I could get more pulling leverage (ever notice the pro sprinters with their elbows sticking out?). To start sprinting, lift your butt off the saddle just enough to clear the tip of the seat and push forward and down on the pedals to begin the acceleration while pulling BACK on the bars. Sort of like pushing against a wall with your foot while pulling on the handle to open a stuck door. As you get up to speed, move your body forward gradually to be more over the pedals which facilitates a faster spin once you're up to speed. You get more "muscle" for the jump by pushing/pulling forward, then move forward to spin and maintain speed.
Gotta love the old "Tashkent Terror", though... Still kickingmyself for not getting his autograph when he came to the Tour DuPont back in '94. I did get a photo with Lance in his World Champ stripes, though, which is cool.