Discussion of using Ankling
for pedaling a bicycle
06 Oct 22 -- subject: "why ankling doesn't work"
Using ankles to help push the pedals adds more muscles, so how could that be bad? Isn't the worst that could happen that the ankle muscles would steal some oxygen pressure from other muscles, and the net result would just be a "no gain"?
That's what I thought, and so I just spent two years working hard on using my ankle muscles lots in my stroke cycle.
I didn't achieve any noticeable gains in speed from ankling, but I kept working on it in faith that one day it would pay off. Then last weekend I was figuring out the dynamical equations of the hip + knee + ankle joints driving the pedal, and as I thought about their implications it hit me that ankling must result in lower total power than non-ankling. Next I looked at the pedal-angle-force measurements from the elite racers, and noticed they were not ankling, rather slightly the opposite -- see the Coyle + Kautz 1991 articles and this diagram for LA: http://www.princeton.edu/~humcomp/bikes/design/desi_76.htm
So three days ago I stopped my ankling. Problem is that I've gotten so good at ankling that it's taking me a while to unlearn it, and I still catch myself lapsing back into it. But the benefits are already obvious, most of all in a whole new freedom in thrusting with my knee-extension muscles (quads etc). Also a bigger range of motion with my hip-extension muscles (glutes, etc), and the fun of easily conquering hills.
Why ankling in the down-push is counterproductive:
Because the role of the ankle thru most of the down-push is to _transmit_ force from the big hip-extension and knee-entension muscles, not to try to add force with its own ankle-extension (a.k.a. "plantar-flexion") muscles. The big upper leg muscles are very powerful, but they're not connected to the pedal. The only way they can transmit their force to the pedal is thru the ankle joint. The only way the ankle can transmit the combined force from the strongest muscles in the cyclist's body is to just do its best try to hold stable (isometric). The other key strategy is to transmit much of the force thru bone rather than muscle. This is done by pointing the toe down before the start of the down-push, so the bones of the length of the foot are partly in line with the main leg-thrust -- and the torque load on the ankle-extension muscles is reduced by getting the ankle joint farther in "radius" from the crank center, closer to the radius of the pedal. My concept for implementing this is . . .
Piston-rod: Before and during the main down-stroke, try to align the length the foot more like a piston-rod, less like a down-push paddle. What's amazing to me in the Lance Armstrong diagram is that despite trying to align his foot-bone somewhat into the push-direction, his ankle joint actually "collapses" during the down-push: It's less extended at the finish than at the start. My interpretation is that LA pushed so strongly with his big hip-extension and knee-extension muscles, that his ankle-extension muscles were not able to fully and optimally transmit all of the power.
[ but see further thoughts in 06-oct-27 post further below ]
Even trying to achieve signicant range of motion of ankle-extension (a.k.a. "plantar flexion") in the down-push is counter-productive -- because it requires first lowering the ankle relative to the pedal before the push, which increases the effective "moment arm" of the pedal from the ankle axis (i.e. gives the force more leverage on the ankle), and which increases the torque on the ankle from the same magnitude of force to be transmitted. But this increased torque is beyond what the ankle could transmit, so the only option is to reduce the force from the big upper leg muscles. I'm pretty sure I did this by unconsciously holding back on the full power of my knee-extension muscles (quads etc) -- which is silly strategy because I've got rather strong quads. No doubt about the result: less total power, lower speed.
Why ankling in the upstroke is counterproductive:
Because the knee is not raised as high, and then the range-of-motion of the big hip-extension muscles (glutes etc) in the following down-push is shorter.
The ankle-flexion (or "dorsi-flexion") muscles (shin, etc) pull the ball and toe of the foot up toward the knee. During the upstroke, if the ankle joint is somewhere near the line from the crank center out thru the pedal, then an ankle-flexion move can reduce the negative torque of the leg's weight on the pedal, and thus add propulsive work. But . . .
The hip-extension muscles push the knee down. Every centimeter the pedal is raised relative to the ankle joint in the upstroke is one less centimeter for the hip-extension muscles to push the pedal through in the downstroke. Work = Force * Distance, and the force of hip-extension is much much more than the force of the ankle-flexion, so the gain of work in ankle-flexion is dwarfed by the loss of propulsive work in hip-extension. Ankle-flexion in the upstroke is a definite loser. My concept for avoiding this is . . .
Piston-rod: Relax the ankle thru most of the upstroke, to use the length of the foot as a piston-rod, not as an up-push paddle. Raise the knee as high as possible.
next . . .
Those are my experiences and thoughts . . . Looking forward to corrections from the experts . . . and better experience stories.
06 Oct 23 -- subject: "why ankling doesn't work"
in response to
The hip-extension muscles push the knee down. Every centimeter the pedal is raised relative to the ankle joint in the upstroke is one less centimeter for the hip-extension muscles to push the pedal through in the downstroke.
But can't they can both push over the same centimeter at the same time?
Yes, the Left leg can make its down-push at the same time as the Right leg makes an upstroke ankle-flexion move.
But I'm not seeing how the Right leg's hip-extension + knee-extension down-push move can occur at the same time as the Right leg's ankle-flexion up-pull move. And that's where I'm seeing the conflict: between the how far the Right knee goes up in the upstroke of the Right leg, and how large a distance you can get between the start and finish of the Right knee during the next down-stroke of the Right leg.
Actually this range-of-motion distance conflict is also a problem for using an ankle-extension (a.k.a. "plantar flexion") move in the down-push. One more centimeter of motion in ankle-extension is one less centimeter of distance available for the hip-extension + knee-extension moves -- during 0-135 degrees, most of the downstroke. Since there's more sustainable power in glutes + quad muscles than the calf muscle, ankle-extension is a _loser_ (even apart from high force transmission problems) -- except maybe for a little somewhere in the lower 135-180 degree range of the down-push.
I'm starting to think that the most critical "bottleneck" resource that determines elite racer endurance _technique_ is the fixed circumference of the path of the pedal.
Tom Compton on August 6, 2000 on this newsgroup wrote: "Work at the pedal comes from force acting through some distance. Moving the ankle trades range of motion of the ankle for range of motion of some other part of the leg. It's the combination of muscle force, mechanical advantage, and range of motion that together act to perform mechanical work at the pedal."
06 Oct 23 -- subject: "why ankling doesn't work"
. . . why not just use slightly longer cranks? . . . and try normal ankling again.
That raises a very good point -- that the choice of ankling strategy depends strongly on equipment configuration -- especially seat height and crank length.
If you used a sufficiently long crank, it would impossible to both remain seated and keep your foot in contact with the pedal thru both Bottom Dead Center and Top Dead Center _without_ making some big ankling moves. But seat height is easier for most of us to play with . . .
If the seat is set low enough, it's pretty difficult while staying on the seat to get the pedal thru Top Dead Center without significant ankle flexion. I could believe there's some less radical seat height where the highest power stroke technique includes significant ankle-flexion near TDC and then significant ankle-flexion pushing during the down-push.
Tendonitis: Come to think of it, I bet that's how I got tendonitis in my left achilles tendon: focusing on ankling, and then setting my seat too low, which made ankling feel more comfortable. I usually don't sprint because I'm long-distance rider, but one time on a mostly-gentle distance ride I got the chance to draft behind a group of riders, and it was fun. Around a sharp corner there was a short steep hill, and the group sprinted, and I didn't want to lose the draft for the following gentle miles, so I sprinted too. I noticed something funny in my achilles tendon, but I had no trouble finishing the ride. But now it's stayed with me for a while.
My best theory so far about how that happened to me is that my unconscious muscle controllers responded to the unexpected sprint demand by thrusting hard with my quads, but my ankle was below the pedal, so it was not at all positioned to transmit the force thru bone. So the torque on the ankle joint was very high, a little too much for my left achilles tendon.
So while playing funny mechanical games with equipment configuration to get around the "conflict over fixed total range-of-motion" problem, I recommend keeping a close eye on the "big force transmission thru the ankle" problem.
So how about "reverse ankling" ... ?
I'm sure I'll get skewered by the experts for saying this, but the key test I would suggest for any refinement of ankle positions or moves or equipment is this: It's good if it helps you feel free to totally mash the hell out of the pedal with the big upper leg muscles.
06 Oct 27 -- subject: "why ankling doesn't work"
I previously wrote
What's amazing to me in the Lance Armstrong diagram http://www.princeton.edu/~humcomp/bikes/design/desi_76.htm is that despite trying to align his foot-bone somewhat into the push-direction, his ankle joint actually "collapses" during the down-push: It's less extended at the finish than at the start. My interpretation is that LA pushed so strongly with his big hip-extension and knee-extension muscles, that his ankle-extension muscles were not able to fully and optimally _transmit_ all of the power.
There's another interpretation of the Lance Armstrong pedaling diagram which I'm starting to like better: It's not that the ankle-extension (a.k.a. "plantar flexion") muscles were "not able" to hold a static configuration for full transmission of the giant force from the big upper leg muscles.
Rather it's a choice to lengthen the range-of-motion available to the big upper leg muscles. Since there's distance between the top and bottom pedal positions is fixed, whether measured in a straight line or around the circumference, different functional muscles groups are forced to compete for a share of the range-of-motion distance available. So the creative strategy here is to make the ankle-extension muscles' range-of-motion _negative_. That leaves "space" for a longer positive range-of-motion Distance by the big upper leg muscles. Since Work = Force * Distance, this longer distance implies more work out of the leg muscles, other things being equal . . .
. . . which they never are: Allowing the ankle joint to collapse a little means that the ankle joint is transmitting _less_ of the upper leg muscles' Force than it could have if it had held rigid. So actually impact on Work is more complicated: there's a little less Force, but a lot more Distance, and there's still a net gain in Work and Power. (Another small point is that there's a small loss in stretching the ankle-extension muscles and tendons, then later shortening them, and this "internal frictional" loss could have been avoided if the ankle joint were instead held rigid through the whole stroke-cycle -- but this is not worth worrying about).
I thank Tom Compton (www.analyticcycling.com) for pointing out the concept of range-of-motion conflict in pedaling technique (in a post to r.b.t back in 2000) -- though I'm not saying he necessarily agrees with my specific applications of it to ankle-flexion and ankle-extension.
Why is it important for racers to know how to maximize total Work to the pedals in each stroke cycle? It seems clear that elite endurance racers have cleverly designed their pedaling technique to (roughly) do that. But why should Work-per-cycle matter, since their true limit is oxygen transport and utililization? Why not accept lower Work per cycle, and just pedal at a higher cadence, to obtain the same Power output to utilize their oxygen capacity?
I think the answer it that some "internal negative work" really is irretrievably negative. The inertial and gravitational "internal" work all nets out to zero over the whole stroke cycle. But negative _muscular_ work does not. The Neptune Herzog 1999 study showed that proportional impact of negative work from unrelaxed (or sloppily timed?) down-push muscles is small at 60rpm, significant at 90rpm, at larger at higher cadences like 120rpm. Therefore higher Work-per-cycle tends to lead to a lower percentage of the cyclist's limited aerobic power (from limited oxygen) going absorbed into muscle-timing problems, so more into the pedals.
I previously wrote:
ankle-extension is a loser ... except maybe for a little somewhere in the lower 135-180 degree range (4:30 - 6 o'clock) of the down-push.
But there can be somewhat of a trade-off between ankle-extension range-of-motion at the end of down-push versus knee-flexion range-of-motion at the start of the backward-and-upward pull, which reduces the possible net gain in work from an ankle-extension move. (That problem is in addition to the requirement to eliminate any intrusion on the range-of-motion of the upper leg extension.)
Anyway I suspect the "window of advantage" (if any) for such an ankle-extension move is so small, that given the "sloppiness" of controlling timing of muscle activation, there's no point in trying to include ankle-extension as a propulsive move in seated pedaling. Has anyone seen a pedaling angle - force diagram or graph which show it being used by a skilled rider?
06 Oct 30 -- subject: "why ankling doesn't work"
However, the only time I tried hard to ankle I ended up with tiring badly my achilles tendons.
Sharon was pedaling indoors and I watched and saw that despite not having down any serious work on technique other than some occasional single-leg pedaling and high-cadence spinning, she had a basically sound technique with her ankles -- slight extension on the upstroke and slight flexion on the downstroke -- which might be called "reverse ankling". She said she never thinks about her ankles. I said that confirmed what I'd read from an expert, that if you just set the seat-position right, the ankles will take care of themselves.
But I couldn't resist asking to show her the technique mistakes she could have made, and she agreed. So in a position in the top quarter of the downstoke, I moved her ankle down to a configuration relative to the pedal where it could deliver substantial positive ankle-extension work and range-of-motion in the downstroke. As soon as she felt the configuration she said, "No wonder you hurt your achilles tendon."
At same output power there should indeed always be a benefit in making more muscles work, provided ... the geometrical set up is sensible
What I found out was that with a normal crank-length and seat-position, the "geometrical set up" is not sensible for getting benefit from ankling on either the upstroke or downstroke of seated pedaling. Yes there's lots of examples in other propulsive sports (skating, cross-country skiing, running) where adding more muscles adds to total power output. But for trying to use ankle-flexion or ankle-flexion moves in most cycling situations, the negative impact on the work from other bigger muscles is larger than the positive contribution from the ankle.