Route Guide - iPhone / Android - Partners - Forum - Photos - Deals - What's New - School of Rock
Login with Facebook
 ADVANCED
one-armed hangboard routine
View Latest Posts in This Forum or All Forums
   Page 2 of 2.  <<First   <Prev   1  2
Follow replies to this topic? Notify me at the top of web site.
1

Email me.
 
 
By Aerili
From Salt Lake City, UT
Apr 10, 2013
Get down from there! <br /> <br />May 2013 <br />Photo by Duc

kenr wrote:
Well I think there are questions where one of us would have to pay (or have an organizational affiliation) to access the full article.

I can get it for free. I am just way busy lately. But I'll pull it up in the next week or so.

I'll write back more later, too!


FLAG
By Greg Kimble
From Colorado
Apr 11, 2013

Heres the full article(2).pdf if you are interested.

Here's an interesting follow up to that Study


FLAG
By kenr
Apr 12, 2013

Greg Kimble wrote:
Here's an interesting follow up to that Study

Remarkable experimental method: They actually used real human fingers to make their force measurements -- taken from cadavers.

I think the key finding for this MP discussion thread is that both the FDP and FDS tendons (and associated muscles) can be very active and effective in both the Open and half-Crimp grips.
(Which lends support to the idea that if you're short on time for a workout, training only one of the two is likely to be helpful for also improving grip strength with the other).

The problem I have with the experiment is that they didn't talk about how they chose to position the MCP joint horizontally and vertically relative to the edge of the right-angle hold which the finger was touching. But for actual climbing the relative position of the MCP is critical for (a) not slipping off the hold; (b) how much muscular force thru the tendons is needed to support the desired percentage of the climber's body weight.

Also, to apply the experimental results to most actual climbing situations, we need to know the _vertical_ component of force between the finger and the hold. But that depends on the overall angle of the finger, which depends on the relative position of the MCP. I'm guessing they used a similar and obvious MCP positioning strategy for all the different grip/edge situations in the experiment. But that's not what real climbers do.

So the fact that one tendon (FDP versus FDS) or grip type (open versus crimp) seemed less effective in the experiment might just be a result of whether a less effective MCP position was used for that tendon/grip/edge combination -- or from not recording the vertical component of force.

I suspect the full version of the original Vigouroux 2006 article cited by Aerili might be more careful about these concerns - (because it's easier to deal with them in the context of a computer simulation than in the flesh).

Greg Kimble wrote:
Heres the full article(2).pdf if you are interested.


This link seems to point to an article about a completely different subject.

I would still be interested to see the full text of the original Vigouroux 2006 article - (but I suspect the bottom line is going to be that both the FDP and FDS tendons/muscles are effectively worked by training with either the half-crimp or open grip).

Ken


FLAG
By Greg Kimble
From Colorado
Apr 12, 2013

Yeah, that's odd. I tried to post it a second time and it switched articles again. Not sure what's going on. I apologize.

Here's a pretty good Study that used MCP posture as an independent variable you might take a look at.

And try this again. julienbruyer.free.fr/M2/Escalade/Articles/sdarticle(2).pdf


FLAG
By Greg Kimble
From Colorado
Apr 12, 2013

That second link SHOULD be to the Vigouroux study. Hopefully it works for you. Not sure what was going on with the other link


FLAG
By kenr
Apr 12, 2013

Greg Kimble wrote:
Yeah, that's odd. I tried to post it a second time and it switched articles again. Not sure what's going on. I apologize. Here's a pretty good Study that used MCP posture as an independent variable you might take a look at. And try this again. julienbruyer.free.fr/M2/Escalade/Articles/sdarticle(2).pdf


Those links work great.
Thanks so much for the extra effort.

Ken


FLAG
By kenr
Apr 12, 2013

Greg Kimble wrote:

Yes seeing the full article really helps. For one it makes clear that the main work was on six human subjects using their real live middle finger to pull on a fairly small edge. The simulation model was only a way to try to infer/calculate the forces in tendons/muscles and ligaments/pulleys which are impossible to measure in a living human.

It also makes clear that the results are a bit tricky -- like there are some very wide differences between the gripping modes of the six climbers in the study.

The overall effort is very impressive. But the calculations are also rather complicated: with 9 unknowns which vary with the gripping situations, and also some key assumption coefficents supposed to be constant across all situations - which must be measured/estimated, especially the moment arm lengths. Not surprisingly, when you throw real biological data at a model this complicated, not everything comes out clean and smooth.

Some odd results:
  • estimated force on A4 pulley for crimp: climber 5 shows over 6 times more than climber 6.
  • estimated tension in FDS tendon for open/slope grip: climber 3 shows over 4 times more than climber 1.
  • climber 3 shows estimated forces way way higher than most of the others for Ulnar Interosseus (UI) and Radial Interosseus (RI) muscles in open/slope grip.
  • climber 5 shows estimated forces way way higher for than the others for Extensor Digitorum Communis (EDC) muscle in crimp grip.
(I'd guess the last two results impact the first two by way of co-contraction).

To me these results suggest that some inputs to the simulation model (e.g. momennt arms) should have been "tweaked" some more -- or add some explicit co-contraction constraints.

Some other thoughts:
  • in absolute numbers, the forces for the Crimp grip on the A4 pulley versus A2 pulley were not all that different - (the Discussion claims that at this level the A4 is much closer to its "maximum" than the A2, but no evidence for that is in the experiments, anyway I'd guess that well-trained climbers have a very different "maximum" for their A4 than most humans).

  • the (obvious) external force applied thru the finger to the hold was about twice as high for climbers 3 and 4 than for climber 2. These were all "national competitive" climbers, 5.13b on-sight. I would not have guessed there would be such a wide range of finger strength in that group. Makes me suspect that some of them found it difficult to be comfortable with the apparatus or the warm-up protocol.

Ken


FLAG
By Greg Kimble
From Colorado
Apr 12, 2013

I was really surprised by the wide range of results as well. I would like to know finger lengths, height, and body weight of each climber. They averaged 5'8", 144 lbs. I suspected weight or anatomical differences in fingers had to do with the wide range. Possibly, climber 2 just has technique that is out of this world. I hadn't considered comfort or psychological reasons. Interesting.


FLAG
 
By kenr
Apr 12, 2013

As I think more (and read the Lee+Chen+Towles+Kamper 2008 paper which Greg Kimble so helpfully offered to us) ...
I'm feeling more concerned about the approach and results of the Vigouroux 2006 paper.

Fundamental to their approach is that they're estimating up to 9 unknown variables (including FDP + FDS tensions) from a 4-equation model -- for the very good reason that with live human subjects it's difficult to actually measure more useful stuff. Typically it turns out that there are many different combinations of values of those unknown variables which satisfy that model -- so in order to draw conclusions the researchers want to choose only one of those for each climber in each grip situation.

Their method of choosing is to take the set of six tendon/muscle tension variables which tends to minimize excessive stress on any one particular tendon/muscle -- where stress is defined as the ratio of tension force to tendon cross-sectional area.

This amounts to a theory of how the human body's unconscious neural control module for the fingers works ... and it seems plausible ... and I'm not seeing an obviously better approach to infer tensions from this data ... but it raises some
Concerns:

a) The cross-section areas of tendons were not measured for each individual climber in the study (for the obvious reason because this would be very difficult in living humans). Rather they came from a 1983 paper which I doubt had anything to do with climbers.
But it's not unreasonable to guess that "national competitive" 5.13b+ climbers have different finger tendon cross-sections than the general population. And some of us might wonder if different climbers have different relative thicknesses based on different training approaches.

(anyway they got different proportions of tendon tensions for different grips and for different climbers, so clearly the relative cross-section areas assumed did not dictate the relative tensions calculated)

b) Then the results about relative tension loads of FDP and FDS tendons/muscles might be partly influenced by their assumption about relative cross-sections built into their solution-selection algorithm.
But really don't we need some prior justification that the human body's neural control modules actually work that way? (Seems to me there are indications that humans often employ non-optimal muscle-force patterns, one reason that Coaches have jobs).

(On the other hand, some of the tensions calculated for climber 3 are so large that I wonder if I've misunderstood the solution-selection algorithm)

c) The article gives results about relative loading on A2 and A4 pulleys. But how do we know that the body's unconscious neural control module for the fingers does not take loading on the A2 and A4 pulleys into account when sending contraction signals to the different muscles? Or maybe the neural module for some climbers does this more than the module in other climbers?

The ratios might have been different if the objective function solution-selection algorithm had included terms for A2 and A4 loading. (But I don't think it's the job of the researchers to include every possible variation on the approach they took -- and I'm surely not going to question the basic conclusion that the Crimp grip puts substantially higher loading on pulleys than the Open trip).

Unrelated specific concerns:

  • the MCP angle shown in the photo for the Crimp grip seems significantly different from what many climbers use in actual climbing moves. (The Lee+Chen+Towles+Kamper 2008 paper gives evidence that changing the MCP angle makes a significant difference in other things relevant).

  • the specific set of numerical tension results which their selection algorithm yielded for climber 3 are just so strange.

Anyway I think the article is valuable, and at the least serves to demonstrate the results from pushing an approach with live human subjects which deserved to be tried. The careful reporting of the detailed assumptions and results should be very helpful for other researchers to consider the pros + cons of this approach.

Ken


FLAG


Follow replies to this topic? Notify me at the top of web site.
1

Email me.
Page 2 of 2.  <<First   <Prev   1  2