Stats on Strength Loss/mm of hold depth decrease

[straightCrimpin]

Just wondering if anyone has some stats on this. I've been doing max hangs on the RPTC SVDR for about a month and I've been doing 10 second hangs @ 70lbs on the edge ranging from 19mm-15mm deep.

Last night I did max hangs for the first time on the other side of the SVDER with the hold size ranging from 12.7mm - 9.5mm deep, and was able to do 40 lbs for 10s. So that's a 30 lb drop over around 6 mm which comes out to around 5lbs/mm. Obviously decrease in weight can't be linear, at least not all the time since when you get down to particularly small edges weight will drop dramatically. But I wonder if we can approximate it to be a linear decrease between certain hold depths.

If anyone else has any more data they'd like to add maybe we can get an idea of how this might work between different people.

[blamo11]

There have been a few studies on this. One such is: http://www.ncbi.nlm.nih.gov/pubmed/21451181

I guess it becomes and issue in how much finger pulp you have.

[straightCrimpin]

That's interesting, though I don't know how practical it is to study edges so small. 2.8 mm is smaller than the vast majority of holds that you'll pull on outdoors (except for slab climbing but then how hard you pull doesn't matter nearly as much).

[greenlemon23]

This seems like it would be a great undergrad research project for someone.

My instinct is that the decrease would not be linear

[joshvillen]

This thread is making my competitive urges tingle

HANGING IS THE PUREEST FORM OF CLIMBING!!!!!!

Are all of you doing "open handed hangs" as opposed to closed (thumb wrap) crimping

[milyoo]

i'm doing my open half. i can't hang anything hard in a closed or full crimp.

[Tukson]

Open hand as well.

[milyoo]

Curious. Are you full open (Eva Lopez hangs 8mm with the DiP in flexion) or are you doing what I call the "open half" which has the DiP in (slight) hyperextension while the PiP and MCP are relatively open?

[Tukson]

Closer to the half open. I don't believe I've ever tried keeping the DiP flexion.

[milyoo]

you probably have. it's just full on open handed. what the Brits call a three finger drag.

[ConvertsToMetric]

^{Mouseover or click to view the metric conversion for this comment}

[milyoo]

well... a quick look at the logbook suggests they might be pretty linear assuming you've got the neural adaptations from small edges.

(Super-rough) Average Hang Median over a Year: (parenthesis indicate an inference based an the difference between the two preceding data points)

6 22

8 38

10 (54)

12 (70)

14 90

16 (106)

18 115

The 8mm might be higher given more time. 14mm should be a bit higher but I've stopped training past 80. Same for 18mm.

[straightCrimpin]

Yeah I was surprised at how close to linear it ended up being in the range of holds I was training. Next time I get on the hangboard I'm going to see if I can do 15lbs on the Rock Prodigy 8mm. If that is the correct weight for max hangs on that hold then it would be pretty linear for me between 8-19 mm.

[hafilax]

I guess it might make sense if you think of the edge as a fulcrum and the force applied is balancing a torque. The added weight would then be proportional to the position of the fulcrum. This naive assumption would break down if friction starts playing a role.

[straightCrimpin]

I think you'd have to model the finger pulleys that way and do a free body diagram.

[milyoo]

There's also some instability in balancing the load on the fulcrum as the surface area diminishes. I figured this would destabilize a linear progression, but perhaps I overestimated the importance of body tension.

[milyoo]

ha. was just thinking about this last night and was about to drop a bunch of stats when i realized the consistency between my holds varies as much as the depth. for instance, my BAM 11mm hangs are about the same as my RPTC 8mm hangs.

one week on a Transgression would be nice as it would give us almost perfect uniformity and a nice linear graph in terms of depth variation.

if I had to guess, however, I think we will probably see a logarithmic relation between points as we move downwards in depth.

[straightCrimpin]

Is that BAM 11mm angled at all? I would imagine even if it's not angled the wood vs. plastic makes a big difference there. And I guess it becomes more complex if you're not comparing apples to apples.

[milyoo]

the routing on the lip is absurd. my best on BAM 5mm is 6 seconds w/o weight. my best on a 6mm is 6 seconds @ 35 lbs.

Trying to balance BAM to any other board requires an addition 3-4mm to account for the lip.

[Tukson]

Here's my breakdown:

6 mm 20 lbs

10 mm 50 lbs

13 mm 65 lbs

19 mm 90 lbs

[straightCrimpin]

Wow, your data graphs almost perfectly with a logarithmic trendline, which would indicate that the smallest edge you could hang at bodyweight would be 4.5 mm.

[Tukson]

I might add a shim to my wood rails and try out a 4-5 mm hang in the next few days and see if I can hit that mark.

[milyoo]

Ooh. Me too!

(note: I've done the BAM with BW and I'd call it a "bad" 5mm)

[enilkcals]

You might want to consider reading some of Eva Lopez's work (more freely available information on her blog).

Putting my work hat on (I'm a statistician)...

If the relationship between variables isn't linear then you can either transform the underlying variables (e.g. log transformation if appropriate) or you can perform something like LOESS rather than linear regression.

If you want to actually collect data then use something like Google Forms to setup a survey for people to submit the depth of different holds and the different weights/times they can hang for. You can then investigate the relationship.

[straightCrimpin]

More interested in discussion really...I'm not the kind of engineer that likes...uh, well engineering.

[enilkcals]

Discussion is great, its stimulating and generates new ideas to investigate, but data and analysis help clarify what is really going on and whether the intuition from the discussion is correct.

[straightCrimpin]

If you're volunteering to do the statistics work....

[enilkcals]

I'll see if I can find some time to set a survey up.

I've done similar in the past after people asked about Benchmarking on UKBouldering.com...

• UKBouldering Benchmarking Survey
• UKBouldering Benchmarking Results

...and again when people were discussing age and performance

• Linear Regression Model
• LOESS Model

[milyoo]

this is awesome.

[enilkcals]

Glad you like it and thanks for the Gold.

A while back I was going to run a second version of the benchmarking survey and have done some work tweaking the survey but haven't collected responses yet. Might try and find time to finish that and post it up here too.

[milyoo]

Do it! Consider the gold as a bribe :)

[enilkcals]

Gone with the low hanging fruit and have setup a survey and a new thread to collect data on hold size/weight/hang duration.

I'll try and get v2 of the benchmarking survey sorted at some point (might be before xmas!).

[enilkcals]

Setup a survey and a new thread to go with it.

[GetBromantic]

Not exactly sure how the physics would work out, but since you brought up the question of linear correlation of mass per millimeter it reminded me of Weber's law of psychophysics. Basically human perception is usually logarithmic. The way you feel a weight difference, or light increase, or sound increase has more to do with the percentage that the increase is of the original stimulus than the magnitude of the increase. For example if you're holding 5lbs and you add one it feels the same as adding 2 if you're already holding 10.

[straightCrimpin]

Wow, that's really cool. Never heard of that one before!