Can Finger Strength Really Be Measured?

A recent scientific review confirms that finger-strength testing is getting more reliable. But between the famous 20 mm edge, portable sensors, and the very real chaos of chalk, putting a climber’s finger strength into numbers is still a serious challenge.

(CC) Brook Anderson / Unsplash

On a hangboard—a training board with small holds—the feeling usually comes before the number. One edge feels sharp. Another bites into the skin. A full crimp loads the fingers a little too hard. Your skin is too thin, the gym is too humid, your fingers are too cold, or the method still hasn’t clicked. One day, the same move feels obvious. Three days later, it makes no sense at all. And yet, over the past few years, a new language has made its way into training logs: kilos, newtons, ratios, asymmetry curves. In fall 2025, researchers reviewed the available scientific literature in a systematic review published in Frontiers in Sports and Active Living, a scientific journal focused on sport, physical activity, and health. A systematic review is a specific kind of research paper: it examines existing studies according to a method defined in advance. Their question was simple: are the methods used to measure finger-flexor strength in climbers actually reliable?

The Problem

The goal of the science here is not to decide whether one number can sum up a climber’s ability. The goal is consistency: if the same person repeats the same test under similar conditions, are the results comparable?

On that point, the answer is fairly reassuring. Fourteen of the 15 studies analyzed reported high reliability for at least one measurement. For maximum isometric strength tests—pulling as hard as possible without moving—12 studies showed very stable results from one attempt to the next. The authors described the reliability as “good to excellent.”

In the 2025 review, fixed 20 to 23 mm edges appeared in eight of the 15 studies analyzed

That finding backs up a broader trend. In 2023, an earlier systematic review on physical testing in climbing had already shown just how central fingers are to climbing research: upper-body and finger-strength tests appeared in 120 of the 156 studies analyzed. But that same review also pointed to a methodological mess. For finger strength alone, researchers counted “almost 230 different ways” to run the tests, depending on the type of hold, its depth, arm and body position, hand spacing, force thresholds, and rest times.

In other words, climbing is swimming in data. But not everyone is measuring the same thing yet. A hang from an edge, an isometric pull on a specific hold, a one-arm test, a two-arm test, a half-crimp protocol—the half crimp is the common bent-finger position between open-hand and full crimp—or an open-hand test can all produce numbers. The question is which numbers can actually be compared.

20 Millimeters, the Gold Standard

In this scattered landscape, one number keeps coming back: 20 millimeters. Along with its slightly larger cousin, 23 mm, that edge depth has become a common reference point in the scientific literature. In the 2025 review, fixed 20 to 23 mm edges appeared in eight of the 15 studies analyzed. The authors found that these depths consistently showed strong reliability and should be prioritized for standardized monitoring.

The 20 mm edge has become a practical measuring unit, linking labs, training apps, portable sensors, and home testing setups. It turns a feeling—“my fingers feel weak right now”—into data that can be compared over time.

Several recent studies have tracked that shift. In 2022, a study published in Frontiers in Sports and Active Living evaluated the Tindeq Progressor, a commercial sensor used to measure force. Twenty-five experienced climbers, 16 men and nine women, were tested in specific positions, including a one-arm pull on a 20 mm edge. Compared with a laboratory force plate, the device scored between 0.90 and 0.99 out of 1 for reliability in the two tested positions.

In plain English: its measurements lined up almost perfectly with the reference device. It was also highly stable when tests were repeated on the same day or several days apart. The authors concluded that the Tindeq can be considered a “valid and reliable” tool for detecting training-related changes in strength outside the lab.

There is also a clear representation problem. The review does not provide a consolidated women-men breakdown across the 747 participants.

A year earlier, a study published in PLOS ONE, a broad open-access scientific journal, showed why these measurements matter so much for training. Fifty-seven male climbers—17 intermediate, 25 advanced, and 15 elite—performed isometric pulls on a 23 mm hold in a half crimp, with the elbow bent at 90 degrees. The result: elite climbers produced greater maximum force than the other two groups. They also stood out for their rate of force development, meaning their ability to generate a lot of force quickly.

For the authors, maximum strength and rate of force development can help distinguish elite climbers from advanced and intermediate climbers.

So the number does not replace climbing. But it is starting to matter in how climbing is trained, tracked, and compared. It is no longer just about whether you can “hold small.” It is about how much force you produce, how you produce it, on which hold, how fast, with which hand, and sometimes how big the gap is between sides.

Still a Guess?

The 2025 review still comes with real limitations. Protocols remain highly inconsistent: one-hand tests or two-hand tests, simultaneous measurements or not, maximum strength, endurance, critical force, rate of force development, hold depths ranging from 6 to 60 mm. The spread was so wide that the researchers did not run one overall meta-analysis. Combining the results would have created a sense of certainty that the protocols themselves could not really support.

For climbers, an even more obvious issue stands out: the lack of control over real climbing conditions. In a sport where a hold that is too cold, too sweaty, or loaded with chalk can ruin an attempt, only four of the 15 studies monitored temperature and humidity across tests. Only one explicitly mentioned chalk use during measurements. The authors noted that cold can reduce finger-flexor performance, especially endurance, and that chalk, which is supposed to dry the fingers, can under some conditions reduce the coefficient of friction.

There is also a clear representation problem. The review does not provide a consolidated women-men breakdown across the 747 participants. That absence is itself meaningful. In the summary table, two studies were male-only, with 93 and 31 men, respectively. One study included men and women without detailing the breakdown there. Another included 31 climbers and non-climbers without specifying participants’ sex. The others included both men and women, but the review does not always make clear whether results were analyzed separately.

That is not a minor statistical detail. The authors wrote that gaps in participant characterization matter because sex and sport experience can influence results. They called for better-balanced protocols, especially for analysis by sex and ability level. The same issue appears in the 2021 PLOS ONE study often cited on strength and rate of force development. It included 57 climbers, but no women, and its authors acknowledged that the results may not necessarily apply to female climbers at the same level.

Finger strength, then, is becoming easier to measure well. But the number still has limits. It isolates one physical ability in a strict setting, on a specific hold, with a specific protocol, under conditions that may or may not be controlled.

It does not see route reading, footwork, stress management, skin fatigue, movement efficiency, or the simple feel for a move. That makes it an excellent diagnostic tool. But we are still a long way from an algorithm for climbing.