On Fri, 14 Jul 2006 20:15:56 -0700, "Phil Holman"
piholmanc@yourservice said:
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Quoted message said:Graham Steer said:
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> On 13 Jul 2006 12:52:38 -0700, [email hidden] wrote:
> Comparing the size of the muscles involved in pushing a leg down to
> those that lift it up adds weight (pardon the pun) to the results of
> the testing.
Runners do pretty well on their hamstrings which are not that
insignificant!
> Of course, you can briefly pull up hard at a low cadence, but you'll
> exhaust yourself roughly twice as fast. At a normal cadence, it
> seems
> to be next to impossible to pull up.
I admit that the only time I really pull is when I am climbing out of
the
saddle.
> Training appears to make little. if any, difference.
The key to this is not pulling per se but avoiding wasting energy by
using
the down stroke leg to lift the weight of the upstroke leg. Single leg
pedalling drills can certainly help here to develop what I understand
to be
the "pedalling in circles" concept.
Dear Graham,
As I understand it, there are two main factors in pedal effort.
First, we move our feet in circles. The effort to raise the back leg
isn't wasted--it's necessary, even with no chain.
It doesn't matter whether we push the trailing leg up with extra
effort from the leading leg that's busy pushing down, or pull it up
with extra effort from the trailing leg that would otherwise be
idle--the same power is required to work both feet in a circle.
Carl, I'll play devil's advocate here. How about if we use just one leg.
We can push down and pull up with one leg and as that leg is supported
by the same cardio-pulmonary system (the limiting factor we hear) then
we should be able to sustain the same endurance power output using two
legs.
Hand crankers cannot match the power output of two legs. Why do you
suppose that the limit to sustainable output is reached exactly at the
utilization of muscles only employed in "mashing". What scientific
evidence is there to support this.
Quoted message said:
(I'm tempted to add that we could pull the trailing leg up with a
string, too, but that would add extra effort--raising and lowering the
arms.)
Second, we add force against the chain.
The chain can't tell which leg the force comes from.
Nor can our cardio-pulmonary system tell which leg is doing the work.
That is, our hearts and lungs cannot produce more power by shifting
the total effort around, any more than a car engine can produce more
power by sending it to four wheels instead of two.
Quoted message said:
Jobst points out that this is why we don't add hand-cranks to bikes.
First, our hearts and lungs won't process oxygen and lactic acid any
faster just because we try to use more muscles. So our legs either put
out less power because of the extra drain from the arms, or else we
reach our cardio-pulmonary limit sooner.
The same thing is true if we try to work leg muscles both ways. If we
add more effort to pull up, we reduce the effort we can put into
pushing down. (That's why pulling up can work on a very short, steep,
non-aerobic climb. Pushing and pulling produces more power, and leaves
us exhausted much sooner.)
I would dispute that. Some of the highest oxygen uptakes have been
recorded by athletes who use both arm and legs (xc skiers).
Quoted message said:
Second, using more and more muscles tends to be less and less
efficient. Bigger muscles handle repeated effort better. (Imagine
trying to climb a hill by repeatedly squeezing handgrips.)
In the case of bicycling, our bodies are not at all efficient at
pulling our heels up powerfully in the tiny pedal circle.
Just about anyone can repeatedly and rapidly raise an impressive
weight by straightening a leg--that's how we climb stairs, raising our
body weight up each step, one leg at a time.
Try to climb the same stairs with that weight attached to either foot.
It will take more than a mind experiment to convince anybody. The
hamstrings and hip flexors are a significant source of input to the
pedal stroke. There was a study a while back that showed significant
increases in gross efficiency although the study was criticized on a
technicality (its hypothesis statement or some such).
Phil H
Dear Phil,
If I'm following, your point is that adding other leg muscles to the
back half of the pedal cycle might increase sustainable power--more
muscle mass, well-trained, could pull up and reduce the strain on the
original leg muscles that only push down.
I do see the reasoning, so I'm willing to be convinced.
But the limiting factor doesn't seem to be muscle mass. The faster
human long-distance riders and runners don't aim for bulked-up legs.
Like pronghorns, they seem to succeed on cardio-pulmonary grounds.
Humans seem to be good at pushing down alternately with two feet, and
two legs work far better than one. So it's reasonable to wonder if
adding a little bit of pulling up and recruiting a few more muscles
would help--if a little is good, more might be better.
But the theory just doesn't seem to test well.
A problem for all such studies is that ideally we'd start with a test
subject who only pushed down and had never heard of pulling up or
pedaling in circles. Then we'd magically have him switch
instantaneously to the scheme that we want to test.
But the training and the results are never instantaneous. Even if the
pulling-up theory is correct, it takes time to condition the muscles
to produce the effect.
It's only after X months learning to pedal in circles or pull up or
use independent cranks that require pulling up that a test subject may
or may not show some improvement.
Is the improvement from the different approach, or just from the
obviously concentrated training? Or a little of both? The skeptics
point out that the results are small at most and should be expected
from that much effort. But the biology is tricky enough that there
could be something going on. As always, I'd like to see something
marvellously clear and convincing and widely duplicated.
(When they first hear about pulling-up, some people head out on a
familiar ride and make a point of trying to raise their feet on the
backstroke and pedal in circles and so forth. They notice a distinct
speed increase for a few miles, but they soon find themselves getting
tired and forgetting to pull up. Is it the cardio-pulmonary system
protesting against the extra effort? Or do they just need to train
long-idle muscles and make pulling-up second nature?)
To drift back to my original point, at normal cadences there's next to
no sign of actual upward pull on the pedals. The upward force seen in
an occasional test subject seems quite negligible compared to the
downward force. For the ordinary rider, there just isn't much evidence
that the proposed technique yields benefits.
Compare the evidence for the benefits of "pulling up" with the
evidence for high cadences. I'm happy on my 45-50 minute ride with my
stately and ridiculously over-geared 60 rpm, but I'm also convinced by
numerous studies that the Tour riders who cruise for hours at 90+ rpm
are not spinning that fast just to look good. The higher cadence
produces a higher sustainable power output.
In contrast, people who believe that they're pulling up strongly have
trouble convincing strain gauges that they're doing so.
Still, I'm willing to be convinced. If you can dig up a link to that
study that you mentioned, I suspect that I wouldn't be the only one to
click on it.
Cheers,
Carl Fogel
