Crimp grips explained: full crimp, half crimp and open hand

Three grips, one edge

Put four climbers on the same 20 mm edge and you will see three different hands. One has flat fingers, knuckles barely bent. One has the first joints stacked up at a right angle. One has the thumb folded over the top of the index finger, pulling hard.

They are not doing the same thing. They are not loading the same tissue. And most people pick between them by feel, without ever deciding, which is how you end up defaulting to the most aggressive option on holds that never asked for it.

Here is what the three grips are, when each one is the right answer, and what the research actually says about which is strongest.

What is under the skin

Your fingers have no muscle in them. The muscles are in your forearm, and they pull on tendons that run down the finger inside a series of fibrous rings called annular pulleys, numbered A1 to A5.

The pulleys hold the tendon tight against the bone. Without them the tendon would bowstring away from the finger every time you closed your hand, and you would lose most of your power. They are the reason a finger can hold body weight on a centimetre of rock.

They are also the thing that breaks. A 2021 review by Miro, vanSonnenberg, Sabb and Schöffl in Wilderness & Environmental Medicine describes pulley injuries as the most common overuse injury in rock climbers, and notes they are rare outside the sport, because almost nothing else loads a finger this way. The A2, A3 and A4 pulleys carry the highest risk, and the review names the crimp grip as the mechanism.

That is the honest starting point. The grip that lets you hold the smallest edges is the grip that hurts people.

Open hand

Fingers relatively straight, the first joints only slightly bent, the pad of the finger resting on the hold. No thumb.

It is the lowest-stress way to hold something, and on anything rounded it is the only thing that works. Slopers, big rounded rails, pockets, most outdoor granite and sandstone. If you can get the whole first pad of your finger onto the hold, open hand is usually available.

It feels weak when you are new, mainly because it is unfamiliar and because you have less feedback from the joint angle. That fades. It also recruits differently, which is why plenty of strong open-hand climbers feel oddly poor on small crimps and the other way round.

Half crimp

The first joints bent to roughly ninety degrees, the fingertips down on the edge, the last joint flat or close to it. Thumb not involved.

This is the position most training is built around, and for good reason. It works on small edges where open hand slides off, it holds a defined shape you can train and measure, and it does not add the extra load that comes with the thumb.

If you only train one position deliberately, train this one. It transfers in both directions better than the other two.

Full crimp

Half crimp, then the last joint of the finger bends backwards into extension and the thumb comes over the top of the index finger and presses down.

That thumb is doing real work. It clamps the stack together and adds force, and on a shallow incut edge nothing else comes close. Full crimp is why some holds are possible at all.

The cost is that it drives the tendon hardest against A2 in particular. It is the position most associated with the injuries in that 2021 review, and it is the one to spend deliberately rather than by habit.

Which is actually strongest

This is where climbers are reliably wrong about themselves.

Zihlmann and colleagues published a study in Current Issues in Sport Science in 2025 that tested 85 climbers, 38 intermediate, 36 advanced and 11 elite, asking them first to predict how their two grips compared and then measuring both. On a 23 mm rung, deep enough to take the entire last segment of the finger, every group and both sexes produced slightly higher force in open hand than in half crimp.

The predictions went the other way. Advanced climbers overestimated their half crimp relative to open hand by 9.8% on the non-dominant hand, with intermediates at 5.6% and elites at 6.3%. So the belief that half crimp is the strong grip is widespread, and on a deep rung it is simply not true.

The depth is the whole story. Earlier work by Winkler and colleagues, testing an 8 mm edge, found half crimp clearly superior. So the two findings do not contradict each other. They mark the ends of a spectrum: once the hold is too shallow for your finger pad, you need the joint angle, and below that the thumb. Above that you do not.

Which gives a rule you can use on the wall. If the whole pad fits, open hand it. You lose nothing measurable, and you spare the pulleys.

Choosing a grip mid-problem

Depth is the first question. Can you get the flat of the first pad on it, or only the tip.

Direction is the second. A hold you pull straight down on suits open hand. A hold you have to pull down and slightly out on, or one you have to hold while your body swings underneath, tends to want a crimp, because the closed shape resists the hold rolling out of your fingers.

Then there is what happens next. Crimping locks the hand in place, which is fine on a static lock-off and bad if you need to adjust, roll onto the hold, or take it in a different orientation than you arrived in. Open hand tolerates being wrong. Crimp does not.

The last question is how tired you are. Grip choice degrades under fatigue, and what it degrades into is usually full crimp, because it is the position that requires the least conscious effort to feel secure in. Sessions four hours long end with people crimping holds they open-handed happily in the warm-up, on worse skin and with less control. That is where a lot of injuries happen.

Training the half crimp without wrecking yourself

The half crimp is the one worth building on purpose, because it is the useful middle and the safest way to get strong on small edges.

Hang it on an edge deep enough that you can hold the shape properly, 20 mm is a sensible place to start, and stop the set when the shape starts to open rather than when you fall off. A half crimp that has quietly collapsed into a drag is no longer training a half crimp, and a half crimp that has crept into a full crimp is training something you did not intend to load.

Progress slowly. Tendon and pulley tissue adapts far more slowly than muscle does, so the forearm strength arrives first and tempts you into loads the fingers have not caught up with. Adding a couple of kilos a month is not timid, it is the actual rate the tissue moves at.

And do not train full crimp on a fingerboard. Use it on the wall where you need it, on real moves, in small doses. There is no version of loading maximally in the most vulnerable position on a static edge that is worth what it risks.

The mistakes worth fixing first

Full crimping everything. By far the most common. Watch your own hands on a warm-up circuit and count how many holds you closed the thumb on that did not need it.

Treating open hand as the beginner grip. It is the grip most of the world's hardest outdoor boulder problems get climbed in, because real rock is rarely a flat 8 mm rung.

Training only what you are good at. If half crimp feels strong you will keep testing it and keep avoiding open hand, and the gap widens. Train the weaker one.

Climbing through a pop. A pulley injury frequently announces itself with an audible crack and a sharp pain at the base of the finger. That is a stop-now, not a finish-the-session. Warm, swollen, painful to load in a crimp: get it looked at rather than testing it every day to see if it still hurts.

No warm-up for the fingers. Shoulders and legs get a warm-up and fingers get thrown straight at a small edge. Ten minutes of easy climbing on big holds first is the cheapest injury prevention there is.

What to do next session

Pick a circuit two grades below your limit and climb it entirely open handed. Every hold that physically allows it, no thumb, no exceptions. It will feel strange on the first four problems and normal by the tenth.

Then do the same circuit in half crimp. You will notice immediately which holds genuinely need a different grip and which ones you had just been crimping out of habit, and that list is the thing worth knowing.

Logging it helps more than it sounds like it should. If you note which grip a project's crux hold actually wants, you stop rediscovering it every session, and you can see whether the small-edge work you have been doing has moved anything. That is most of what we built the tracking in Sendit for, and grip is one of the details that quietly decides whether a hold goes.

Sources

• Miro PH, vanSonnenberg E, Sabb DM, Schöffl V. "Finger Flexor Pulley Injuries in Rock Climbers." Wilderness & Environmental Medicine, 2021;32(2):247-258.
• Zihlmann C, Ritsche P, Feldmann A, Reissner L, Keller M, Wolf P. "Open hand vs. half-crimp: Do climbers assume differences in their own maximal finger strength that do not exist?" Current Issues in Sport Science, 2025;10(1).