Why Finger Pulp, Not Tendon Strength, Makes for Better Crimping - Climbing Magazine

Why Finger Pulp, Not Tendon Strength, Makes for Better Crimping

Everything you never knew you wanted to know about fingertip “squish.”
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When we think of our ability to bear down on small holds, we usually think of tendon strength. But the study “Measuring Lifting Forces in Rock Climbing: Effect of Hold Size and Fingertip Structure” (Roger Bourne, et al.; Journal of Applied Biomechanics, 2011) suggests that high-level climbers’ ability to crimp micro-edges may, surprisingly, be mostly about the amount of soft tissue (“finger pulp”) in their fingertips and the friction created when their tips deform (“squish”) to accommodate the shape of the edge.

Rock Climbing Fingertip Pulp Finger Anatomy

The more "pulp" between your bone and your skin, the better you can crimp.

Beefier Is Better

The study found that meatier tips are an advantage for crimping. This is because the smallest holds only accommodate your very fingertips, where there are no bones and where friction—not tendon strength—reigns supreme, courtesy of that easily deforming soft tissue.

Climb Like a Girl

The finding that friction is the most influential factor in crimp strength led researchers to speculate that it’s generally women’s softer, thinner skin (on average 25 percent thinner than men’s) that lends them their edge at crimping. The same logic may also explain young crushers’ notable crimping ability. Children have significantly thinner skin than adult men or women, with an infant’s overall skin thickness around one-fifth that of an adult’s. Skin continually thickens until about age 50, meaning that younger climbers could have a slight advantage on tiny edges.

Uniquely Symmetrical

There was no significant strength difference between climbers’ dominant and nondominant hands, likely the result of years of climbing, through which favoritism is eliminated.

12.5mm

The size (about ½ inch) of the largest holds used, selected because it was determined to be universally “comfortable,” making strength, rather than pain tolerance or friction, the limiting factor in force production. 

5

Minimum number of years of climbing experience required to participate.

Measuring Tip Squish

Using ultrasound, researchers found that individuals with the greatest “bone to tip pulp dimensions” (i.e., the most soft tissue between the tips of their finger bones and their fingertip skin) displayed the greatest force production on the shallowest edge (2.8mm). To measure force production, participants performed single-hand dead-hangs on crimps while standing on a scale. The weight displaced was then calculated relative to their bodyweight to reach body mass-normalized lifting force (i.e., strength-to-weight ratio).

3–5 minutes

The time you’ll waste staring at your tips after reading this article. Researchers noted that external examination of climbers’ tips showed a wide array of shapes, but was inaccurate in gauging bone position—i.e., you can’t measure finger pulp just by looking. 

15

Number of participants in the study—11 men and 4 women, a small sample. 

File Away

Given that a more flexible tip is advantageous, researchers speculated that fingertip calluses might be a disadvantage on crimpers. Start sanding! However, only take off the top layer—it undermines friction gains when your fingertips weep white blood cells. 

5.8–7.3mm

Size range of the edges on which the most skilled participants (5.13 and 5.14 climbers) showed the greatest force production, consistently outperforming 5.11 and 5.12 climbers. However, on larger or smaller edges, there was no significant difference. This might be because the smallest holds on 5.13s and 5.14s rarely fall outside this range, and so climbers around this level are specifically adapted to pull on holds of that size. 

5.11a–5.14a

Hardest recent redpoints as reported by the study’s participants.

36.5

Mean age of participants, with a standard deviation of 9.4 years.

2.8–4.3mm

Or roughly 1/10 of an inch, the size of the smallest edge used in the study. Testing demonstrated no significant correlation between max force production, measured on the 12.5mm edge, and force production here. This finding seems to support the “common knowledge” that max strength is a poor predictor of performance on climbs in which the challenge is micro-crimping. 

Fat Fingered

Researchers factored in strength-to-weight ratio to ensure the greater force production of meaty-tipped climbers was not negated by higher bodyweight. In so doing, not only did the above assertions remain true, but bodyweight had no correlation with the amount of soft tissue in your tips.

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