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crimp grip wrist position


Original Post
kenr · · Unknown Hometown · Joined Oct 2010 · Points: 14,459

The key grip lots of us use for hanging on small edges is the crimp.
. . (with the tip link and joint of each finger bent out in an hyper-extended position,
. . . while the other finger joints are in a "normal" flexed configuration).

Wrist position?
Which is better:
(a) wrist joint down vertically (roughly "neutral") under the base of the fingers;
. . . or . . .
(b) wrist pressed under (into "extension") close to the wall, or even up under close toward the fingertips.
. . .(like see time 4:44 in the famous Jan Hojer training video).

Of course (b) takes lots more effort (by the wrist extensor muscles), especially when lacking usable footholds.
. . . (? implications for training?)

I'm going to argue for (b) as superior in many situations, because: 

1) In a temporary static hanging situation (e.g. while re-arranging feet for the next move, or making a clip), maintaining the wrist in an extended position puts two substantial bends in the path of the finger flexor tendons (keep in mind that the muscles that drive the pulling of the fingers are located remote back in the forearm). Making the tendon go across each bend adds friction, therefore less work needed from the muscles to hold a static grip position.
. . . One bend is across the Carpal-MetaCarpal joint, the second is across the MetaCarpal-Phalangeal joint.

2) The forefinger (but not the other fingers) has a strange configuration for connecting at least one of its flexor tendons, so it applies force best with the wrist joint in an extended position (and badly with the wrist in a flexed position).

3) If first "set" the fingers in crimp position on top of ah edge hold with the wrist in a "neutral" position under the base of the fingers, and then move the wrist into extension (toward the wall and more under the tips of the fingers), that will slightly pull on the finger flexor tendon (by lengthening its required path), and so add a little bit more force to the crimp-grip fingers.

4) The wrist joint is say about 1/4 inch _higher_ in position (b) with the crimp grip. So the shoulder can be higher -- and so the other hand can reach 1/4 inch higher to latch the next hold. And the hips can be higher, so the foot can make it to step up onto a hold a 1/4 inch higher.

I'm thinking either This is just wrong somehow;
or Expert climbers already do it instinctively, seems obvious to them;
or Top coaches have long been teaching this, I just missed it somehow.

Ken

Wolf L · · New York, NY · Joined Nov 2017 · Points: 41

I think this is reasonable. There is no question that b is more aggressive and generates more force. To generate even more force one can use the full crimp with the thumb on the edge as well.

But the advice I got for general climbing is always to use the least aggressive method possible to avoid the pump and injury. 

Mark E Dixon · · Sprezzatura, Someday · Joined Nov 2007 · Points: 569

I'm not sure I'm convinced by the friction argument. I'm pretty sure healthy tendon sheaths are pretty slick. Don't know if there's data anywhere.

IIRC, the length/tension curve for the forearm flexors show increasing strength for increasing length, so extending the wrist would be expected to increase flexor strength. 

Isn't that the explanation for why we chicken wing when fatigued?

@ Wolf- There is a study that shows a noticeable increase in strength when you add the thumb in full crimp. But with increased stress on the index finger IIRC.


reboot · · . · Joined Jul 2006 · Points: 125
kenr wrote:(b) wrist pressed under (into "extension") close to the wall, or even up under close toward the fingertips.
. . .(like see time 4:44 in the famous Jan Hojer training video).

I assume you are talking about this:

Note: at the angle of the wall, this incut crimp is essentially a sloper.

4) The wrist joint is say about 1/4 inch _higher_ in position (b) with the crimp grip. So the shoulder can be higher -- and so the other hand can reach 1/4 inch higher to latch the next hold. And the hips can be higher, so the foot can make it to step up onto a hold a 1/4 inch higher.

You are missing the point here. The primary reason for the wrist position is akin to ankle position on a foot hold: apply force in the direction of friction. Pulling down on a hold more parallel to the wall (which also sucks the body closer to the wall) allows better utilization of friction for both the hand hold and the foot hold. The 1/4 inch difference pales in comparison to how much higher you can pull up (rise in COG) before you hand would pop off the hold.

kenr · · Unknown Hometown · Joined Oct 2010 · Points: 14,459
reboot wrote:

The primary reason for the wrist position: apply force in the direction of friction. Pulling down on a hold more parallel to the wall (which also sucks the body closer to the wall) allows better utilization of friction for both the hand hold and the foot hold.

I agree that (other things being equal) the more force applied perpendicular to the top surface of a planar hold, the higher the friction; Also the less force outward tangential to the top surface, the less likely the finger will slip off.

But what does wrist angle/position have to do with either point?

No matter what the extension or flexion or neutral angle of the wrist, if the climber's body and hands are currently static, the vertical downward component force is the climber's body weight less any friction of the feet touching the wall. So take the simplest case of a dead free hang with neither foot touching, then the vertical downward component is exactly the climber's body weight (with gravity) and the tangential force outward is pretty near zero - (because if the climber's Center-of-Mass were not vertically under the finger-crimp hold, the climber's body would be swinging, not static). Whatever the angle/position of the wrist, the climber compensates with other body parts (e.g. elbow or shoulder) to the Center-of-Mass into pretty much same position. Our bodies are mechanically complicated, so wrist position/angle can be mostly independent of Center-of-Mass position.

With a foot touching, the force components get slightly more complicated, but the same point applies: Wrist angle/position is not important for friction, because there's so many other ways to compensate.

Ken

P.S. A different but related argument might be that the extended wrist angle/position allows the PIP joint of the crimping finger to support the same components of force at the fingertip-to-rock contact point, but with better _leverage_ so it requires less torque through that joint. But my own analysis of the static forces / moments of the kinematic chain did not support that argument -- but that sort of analysis can be tricky, so I'd be glad if someone found otherwise and explained it for us all.

kenr · · Unknown Hometown · Joined Oct 2010 · Points: 14,459
Mark E Dixon wrote:

I'm not sure I'm convinced by the friction argument. I'm pretty sure healthy tendon sheaths are pretty slick.

Question I would have is: Dynamic sliding friction versus Static holding friction.

Different for different pairs of substances at an interface of the same shape. Some pairs are low in both, some are high in one and low in the other.

I agree that healthy tendon sheaths are low in Dynamic sliding friction. For Static holding friction, not so obvious whether higher or lower is advantageous for biological survival and reproduction success. Might even be that tendon sheaths for fingers are different from legs -- that finger tendon sheaves have higher Static friction -- since there are obvious _human_ survival + reproductive advantages to be able to _hold_ a static grip around a tool . . . or weapon.

Ken

P.S. Sorry about this long delay in my response. Just after my initial post, I got thrown into organizing the response to a big life change of an aging parent.

kenr · · Unknown Hometown · Joined Oct 2010 · Points: 14,459
Mark E Dixon wrote:

the length/tension curve for the forearm flexors show increasing strength for increasing length, so extending the wrist would be expected to increase flexor strength. 

I'd love to get a link to some studies for that.

Myself I find that to be true for my thumb-forefinger pinch strength, comparing wrist-flexed versus wrist-extended (tho not so much comparing wrist-neutral versus wrist-extended).

But with my thumb-middle-finger and thumb-ring-finger pinches, I don't notice any difference in strength between wrist-neutral versus wrist-extended, and at most pretty small difference between wrist-flexed versus wrist-extended.

. . . (anyway wrist-flexed is a fairly unusual hand-arm position in actual climbing).

Mark E Dixon wrote:

> Isn't that the explanation for why we chicken wing when fatigued?

This sounds to me like a whole other topic: "Why does chicken-winging work?"

Chicken-winging is such a major change in arm and body position, it has multiple impacts on fingertip-to-rock-edge friction and muscle-joint leverage advantage. I can quickly think of two other explanations for why chicken-winging can extend the duration of sustaining a crimp grip.

Ken

Mark E Dixon · · Sprezzatura, Someday · Joined Nov 2007 · Points: 569

Here's a reference for wrist extensors.

http://muscle.ucsd.edu/More_HTML/papers/pdf/Lieber_JEK_1998.pdf

Best I could find with a quick search for finger flexors.

http://downloads.lww.com/wolterskluwer_vitalstream_com/sample-content/9780781774222_Oatis/samples/Oatis_CH04_045-068.pdf

See figure 4.15 and the Clinical Relevance sidebar on page 55.

Joe Garibay · · Ventura, Ca · Joined Apr 2014 · Points: 96

I wonder if Honnold or Caldwell or Potter or etc... (too many names to list) ever thought about grip position. I think you will gain something from this science but I also think you just need to climb the way you’re designed to climb. Don’t over analyze. Practice practice practice and make it second nature. Soon enough you’ll forget all about where your wrist is. 

Edit to add: or am I doing it wrong? Always go with natural instinct, but always observant towards other possibilities. I deny nothing. Sometimes the worse advice is your best advice. 

J Squared · · santa barbara, CA · Joined Nov 2017 · Points: 0
kenr wrote:

I think you should watch the video again, and play in slo-mo.... 

his wrist doesn't actually go into "extension" for more than a split second at 4:44... he first hits it with a 3finger open grip, then pops his hand a bit to grab and engage with the thumb.


Guideline #1: Don't be a jerk.

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