Climbing Notes
Holds and how to use them safely

Grip positions: open hand, half crimp, full crimp

How you bend your fingers on a hold changes where the load goes. The crimp positions feel secure, but they put far more force through the pulleys that hold the tendons against the bone.

3 min read 5 sections

In plain words

The tendons that bend your fingers run along the palm side of the finger bones, held in place by small bands called pulleys. When you bend the middle finger joint sharply, as in a crimp, the tendons pull hard against those pulleys, like a rope over a pulley wheel. In an open hand the joints are only gently bent, so the pulleys carry much less. The full crimp, with the last finger joint bent backwards and often the thumb wrapped over, loads the pulleys most of all.

Memory hook

The sharper the bend, the more the pulleys pay.

The three positions

Open hand A2 pulley Low pulley load
Open handFingers gently bent; skin and friction do the work
Half crimp A2 pulley Moderate pulley load
Half crimpMiddle joint near 90°, last joint straight-ish
Full crimp A2 pulley Highest pulley load
Full crimpLast joint bent backwards, thumb often wrapped over
The circle marks the A2 pulley; its size is a rough guide to how much load it carries, not a measurement.
Open hand

Joints gently bent. Least pulley load. Good on slopers, pockets and rounded edges; feels insecure on tiny edges at first.

Half crimp

Middle joint near 90°, last joint fairly straight. A common all-round position; noticeably more pulley load than open hand.

Full crimp

Last joint bent backwards, thumb often over the index finger. Most secure on tiny edges and highest pulley load.

Where the pulleys are

Finger seen from the side: bones, pulleys A2 and A4, and the growth plates Hand bone Proximal phalanx Middle phalanx Distal phalanx Flexor tendons run underneath, held to the bone by pulleys A2 A4 Growth plate at the base of the middle phalanx
The A2 pulley sits on the first finger bone and the A4 on the middle one. In young climbers the growth plate at the base of the middle bone is a separate weak point (see growth plates).

The evidence

Numbers from adults only.

  • Measured In the crimp position the A2 pulley carried about 3 times the force applied at the fingertip, and loads of up to 116 N were measured over it. A warm-up increased tendon bowstringing over the A2 pulley by 0.6 mm (30 %). Schweizer 2001: 16 fingers of 4 adults, measured in the living hand. J Biomech 34(2):217–223.
  • Measured A biomechanical finger model estimated forces on the A2 pulley 36 times lower in a slope (open) grip than in a crimp grip, and on the A4 pulley 4 times lower. Vigouroux et al. 2006: a three-dimensional finger model with measured inputs; the abstract doesn't give the number of participants. J Biomech 39(14):2583–2592.
  • Measured Pulley injuries are the most common overuse injury in rock climbers, and the crimp grip is the mechanism. Miro et al. 2021, a review. Wilderness Environ Med 32(2):247–258.
  • Coaching practice Learn to use open hand and half crimp on most holds, and keep the full crimp for when nothing else works.

Try it

Drill

Silent feet. Better footwork means less weight on the fingers.

Next read

Finger injuries, and Growth plates for young climbers.

Common mistakes

Crimping by habit

many holds work in half crimp or open hand with less pulley load.

Full crimping cold

the warm-up measurement suggests the finger changes as it warms up. Build up gradually before small edges.

Thumb-locking on every small edge

the most secure position is also the heaviest on the pulleys.

Teaching young climbers to full crimp

in growing fingers the growth plate is the weak point under crimping; see growth plates.