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.
What's here: My story / Why down-push ankling is bad / Why up-stroke
ankling is bad.
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.
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* 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.
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.
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* Why ankling in the up-stroke 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.
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Those are my experiences and thoughts . . . Looking forward to corrections
from the experts . . . and better experience stories.
Ken