benefits of wasted motions

Ken Roberts kirjoitti:

I'm not getting some of this analysis of double-poling.

Probably not your fault:-) My short and superficial introduction to the
subject took place during a run with a guy who'd just read an article
about it in a running/skiing mag, which means the analysis was dumbed
down and mangled thrice by the time it reached your eyes...

But if I managed to whet your appetite, you can have a look at the
scientific presentations held during the International Congress on
Science and Nordic Skiing in Vuokatti: http://www.icsns2006.fi


Anders

Ken Roberts wrote:
Peter H. wrote
Wouldn't the muscles of the lower back and abdomen
do far more of the 'gravity work' in double-poling than
the legs?

Definitely the lower-back-extension muscles do some real work in lifting the
mass of the chest + shoulders + head + arms against gravity.

You've done a careful analysis on this, Ken, and although
I'm not so sure on your knee-bend data below, I recall that
you did some excellent times in the world Masters at Quebec
a few years back, and they were DP-fests, so I have every respect
for your 'double-poling opinions'.

However ...


but the Hip-extension muscles also lift the mass of the chest + shoulders +
head + arms -- and additionally the mass of the lower back. (provided that
the skier allows the mass of the upper body to hinge forward from the
hips -- as Kris Freeman and the other World Cup racers are doing big-time
(hip-joint range-of-motion from 0 to 90 degrees) in the JanneG double-poling
technique video I'm looking at now.

The Knee-extension muscles also lift the mass of the chest + shoulders +
head + arms -- and additionally the mass of the lower back + upper
abdomen -- and additionally the mass of the hips + pelvis region.
Provided that the skier allows the hips to drop down + back and the knees to
bend substantially -- as Kris Freeman and the other World Cup racers are
doing obviously (knee-joint range-of-motion from 0 to 45 degrees) in the
JanneG double-poling technique video I'm looking at now.

You haven't written out the complete calculation below
[since you assume we can all multiply
(in the arithmetical, not the copulative sense!)
and can supply our own mass figures].
But are you not maybe implying that
we calculate the work of the hip-extensors,
ASSUMING they do all the work,
and the same for the lower back, assuming IT does all the
work??
The crucial issue would be how that work is distributed,
since of course it isn't done twice, once by each.
And I guess I am maintaining that,
from the subjective feelings of fatigue I feel in those two areas,
the back is doing by far the larger proportion of the work.

I'd also add that, in any case, it's a moot point
whether one should regard the hip extensors as legwork levers
or body-core-work levers.


Since physical Work against gravity = Gravity * Mass * Distance, we need to
also consider the vertical distance of each motion:
* for Lower-Back-extension, looks to me like the range-of-motion is from 0
to 30 degrees. Let's say for the sake of argument that the skier's height is
180cm, and the "rotational joint center" of the lower back is 35% below the
top of the body, and the average radius of the center-of-mass moved by lower
back extension is half of that, or 31.5cm, so 30 degrees gives a maximum
vertical distance about 16.25cm.
* for Hip-extension, the net angle (combined with knee flexion) from
vertical is 45 degrees, so if the hip joint height is 50% of body height,
and radius of average center-of-mass is half of that, then the trigonometry
yeilds a vertical distance of 13.5cm
* for Knee-extension, the angle from vertical is 45 degrees, so if distance
between knee-joint and hip-joint is 20% of body height, the trigonometry
yields a vertical distance of 10.8cm.

Seems to me that the physical Work against gravity done by the Hip-extension
muscles is going come out roughly similar to the Work done by the
Lower-Back-extension muscles, since one has more mass and the other more
distance.

As for knee extension work, I never downloaded anything
after a point a few years back,
so the videos I checked are from the immediately
previous generation mostly of male WCers.
But I see nothing even close
to that 45 degree range of motion
in the kneebend of any of Myllylla or
Eloffson or Skjeldal or Hjemeseth (sorry for spelling errors!),
in some clips I have labelled "short,silent"
(probably my labels, not Janne's).
I'd say much closer to 10 degrees.
It would be interesting to know if
there's been some major change in the theory
of this venerable old technique very recently.
In any case (without wanting to sound catty),
probably Freeman's results in the last couple of years don't make him
one whose emulation inspires the most confidence.

Therefore including the Knee-extension work
puts the legs far ahead of the upper body in "gravity" work for elite
double-poling.
(and that's not counting Ankle-extension work)

I've done plenty of LSD intensity double-poling
for maybe 10 km. at a time on fairly flat terrain,
and never felt any fatigue in the legs at all.

It's certainly possible to double-pole without dropping the hips much -- I'd
guess that's how most XC skiers do it most of the time. I know the top
Canadian coach for a different propulsion sport told me that people normally
over-estimate how far they are lowering their hips.

How about post a video of a side view of your double-poling?

Ken

The only website I put stuff on probably shouldn't have that
kind of stuff, and all I have is an older digital still camera with
mpeg mode.
But I have done some for my own purposes,
setting it up on the tailgate of the Element,
and I'll get my wife to do a few side shots soon.
Then I'll try to do post them,
when the lady who puts stuff on my website gets back
from her holiday in Costa Rica.
Who knows, maybe I can even wheedle a bit of coaching out of Nathan,
though I shoudn't expect it from a real professional for free!
(And he's possibly way over in New Zealand, where Freeman
nearly lapped me in last year's big Snowfarm race, so I really
should watch those smart-ass remarks above!)

Best, Peter

Peter H. wrote
You haven't written out the complete calculation below

Because really you need diagrams to follow the trigonometry, and it's too
much work to do a good job of creating them and putting them up on the Web.
(and I'm not eager to do the work because despite double-poling being key to
my strategy back when I cared about Classic racing, I just don't enjoy doing
it much any more.)

But are you not maybe implying that
we calculate the work of the hip-extensors,
ASSUMING they do all the work,
and the same for the lower back, assuming IT does all the
work??

My calculations are for the _incremental_ contribution of each muscle group
in elite D-P technique to the total vertical distance of motion of various
body parts.

I'd also add that, in any case, it's a moot point
whether one should regard the hip extensors as
legwork levers or body-core-work levers.

I think the biggest muscle for a true hip-extension move is the gluteus
maximus. I believe most athletes and coaches think that's a _leg_ muscle.

For those who still think that the contribution of the legs to double-poling
is minor . . .

(A) How do you explain this point in Anders' post last week?
(2) the oxygen consumption of leg muscles is
greater than that of upper body muscles

(B) How is that I remember an article in the Master Skier magazine in the
last couple of years or so which said to think of double-poling as like a
standing broad jump?

(C) How is it possible elite racers for elite racers to generate sufficient
Watts out of their muscle mass while refusing to get major utilization of
the large muscle mass of their legs -- so they can go faster double-poling
on gentle terrain than striding? After you exclude the legs, I doubt there's
enough muscle mass in the rest of the body to produce 300-400 Watts output.

Ken

Anders wrote
My short and superficial introduction to [ double poling ] . . .

Actually (despite my rambling post) I agreed with most of it,
including the final point that neuromuscular training is needed to get the
muscle speed required for elite performance on flat terrain -- so that
uphill DP workouts are not sufficient. (Richard Taylor makes that point
about Classic technique generally in his book "No Pain, No Gain?")

My only difference is that I see legs as core to double-poling, not wasted
motion.

you can have a look at the scientific presentations held
during the International Congress on Science and Nordic
Skiing in Vuokatti: http://www.icsns2006.fi

Conference topics look interesting, but they don't have links to the slides
or papers.

Ken

Ken's view on the question of leg muscle gravitational contribution
overall to DP propulsion have become just a bit more
convincing to me, not a lot, and mainly as a result of
thinking back to a few instances of me doing stuff on
rollerskis and closely monitoring heartrate response.
And I'd drop the "gravitational" there, and think of it more
as forward propulsion done directly with the hip joint
(that "sex machine" wiggling mentioned a long time
ago as also being a bit of a remedy for lower back
ache in DPing).

Also the sports scientists have to be correct some of the time,
and maybe these particular ones this time are, and the
3rd or 4th hand reporting is accurate. I myself can't imagine
how the scientists manage to determine how much oxygen
consumption different muscles use, rather than merely
the total consumption, in a given activity. I assume it's
actual measurement, not some theoretical exercise
in trigonometry, such as Ken has half-given and which
I question somewhat below. If it is actual experimental
measurement, I don't suppose it's just the usual breathing
apparatus they attach to subjects. After all, the individual
CO2 molecules don't come out of the subject's lungs with
tiny labels saying something like "My goodness, I'm
yet another one that got created in the muscle of Ken's
middle toe on his left foot---he sure does use those toe
muscles a lot in his skiing, as he's been suggesting so often
to the RSNers!" If anybody here can quickly explain to me
how the scientists are able to make this distinction between the
oxygen consumption of different muscles in the same
activity, I'd be grateful. And by "same", I mean simultaneous,
not some unconvincing rigamarole where you first get them
to try to use all back and no butt, and then get them to do
the opposite. That would be reminiscent of, and even worse
than, the silly measurements we discussed a year ago
of scientists having people doing offset in fast flat terrain
just to compare it to 2-skate.



Ken Roberts wrote:
......
Because really you need diagrams to follow the trigonometry, and it's too
much work to do a good job of creating them and putting them up on the Web.
(and I'm not eager to do the work because despite double-poling being key to
my strategy back when I cared about Classic racing, I just don't enjoy doing
it much any more.)

But are you not maybe implying that
we calculate the work of the hip-extensors,
ASSUMING they do all the work,
and the same for the lower back, assuming IT does all the
work??

My calculations are for


the _incremental_ contribution of each muscle group
**(See below--Peter)**


in elite D-P technique to the total vertical distance of motion of various
body parts.


As for the trigonometry, I picture my DPer for this
purpose as a stickman with 3 nodes or joints,
namely the ankle, knee, and hip level; with these
connecting 4 line intervals, namely foot, shin/calf, thigh,
and top. We're talking only about work against gravity,
which is entirely summarized in raising from a more
horizontal to a more vertical alignment
(1) the shin and/or thigh (very, very little I claim), and
(2) the top (almost the entire effect, I claim).
Surely the rotation of a given joint can at most involve
the muscles on the two 'line segments' connected to it.
Let me bore you even more by spelling out explicitly
what this says:
thigh/butt and top muscles have nothing to do with rotating the ankles;
foot and top muscles have nothing to do with rotating the kneejoint;
foot and shin/calf muscles have nothing to do with rotating at the
hipjoint.

Since 'verticalizing' the top is the only effect of any real
significance here (Ken didn't seem to object to my
correcting his 45 degrees to 10 degrees for the kneejoint in DP),
we are left with figuring out how much is done by the
leg muscles (below Ken refers to the arse muscles, more specifically
glut. max.), and how much is done by the core. This is where I simply
cannot figure out how these proportions can be determined
simply by trig. I really need a hint for doing this homework
assignment.

The only thing I can conjecture is that Ken's stickman has
another joint somewhere in the middle of his back,
where he talked earlier about the position
of the back muscle,
and that somehow it can only lift stuff [like the adam's apple]
which is above it,
and not things [like the (hopefully minimal) contents of the bowel]
which are below it.
But that doesn't sound too likely, either as a reasonable model,
or as anything Ken would come up with.



I'd also add that, in any case, it's a moot point
whether one should regard the hip extensors as
legwork levers or body-core-work levers.

I think the biggest muscle for a true hip-extension move is the gluteus
maximus. I believe most athletes and coaches think that's a _leg_ muscle.


I'll grant you that!



For those who still think that the contribution of the legs to double-poling
is minor . . .

(A) How do you explain this point in Anders' post last week?
(2) the oxygen consumption of leg muscles is
greater than that of upper body muscles

As mentioned above, I need some more convincing
that they really _know_ that.



(B) How is that I remember an article in the Master Skier magazine in the
last couple of years or so which said to think of double-poling as like a
standing broad jump?

Fine, but gravity in broadjumping is the enemy, not a help.
See end of my first paragraph above.



(C) How is it possible elite racers for elite racers to generate sufficient
Watts out of their muscle mass while refusing to get major utilization of
the large muscle mass of their legs -- so they can go faster double-poling
on gentle terrain than striding? After you exclude the legs, I doubt there's
enough muscle mass in the rest of the body to produce 300-400 Watts output.

Look up hand-crank bicycles---well over 40 km/hr. is quite
possible. You'll say "It's the vastly more efficient mode
of a bike compared to skiing".
And I'll say "Precisely: the answer to your question
above is the vastly superior efficiency of DPing to striding".


Best, Peter

Peter H. wrote
I myself can't imagine how the scientists manage to
determine how much oxygen consumption different
muscles use, rather than merely the total consumption, in a given
activity.

Yes, now that you mention it, how did they measure that result about upper
body versus legs?

:-) How about different carbon isotope ratios for UB versus legs?

Ken