The one way to truly rest on a hand jam

Hey Cracksters,

Today I want to address a fundamental issue I've seen pop up in coaching recently: finger fatigue or pain whilst hand jamming

I’ve had a couple of people say recently that their fingers are aching or tired after crack climbing (specifically on hand sized cracks). This isn’t usually a strength issue, it's a pressure distribution mistake. If your fingers hurt, you are almost certainly relying too heavily on pressing with your fingers, rather than expanding with your thumb.

The Hand Jam: Why Your Fingers Hurt

Many climbers, especially when starting out, push hard with their fingers as using their fingers is what they are used to in normal climbing. By doing this they neglect the all important thumb muscle

The result: Hyperextension and painful strain on the back of the finger joints

The Hand Jam Percentage Rule (70/30)

For hand sized cracks I always say you want to be thinking about the pressure you are applying with thumb and fingers like this:

70% Thumb Expansion / 30% Finger Pressing

Your thumb is the powerhouse! It creates the expansion that locks your hand firmly into the crack. The pressure from your fingers should be minimal, it is there for the extra 20-30% to make the jam feel completely bomber. In a perfect hand jam you should be able to hang easily off the jam without the opposing pressure of the fingers.

If you feel like your fingers are hyper extending or feeling strained, the most likely reason is that you are pushing too hard with the fingers, and not giving enough attention to the thumb.

What About Cupped Hands?

As the crack opens up to cupped hands, the percentages change because you have a bigger space to fill and the expansion of the thumb alone isn’t enough to fill this effectively.

In this wider size, the lock becomes a more balanced system, roughly:

• 33% Thumb Expansion
• 33% Finger Pressing
• 33% Rotational Twist (Hand or Forearm)

Even here, the principle holds true: Never default to high-force finger pressing. Make sure you are balancing the strain by expanding the thumb pulp (as you would in any hand jam), but also twisting the hand and forearm across the crack.

If you’re noticing finger pain after a session, ease up on the ‘finger pressing’ and really think thumb, thumb, thumb.

I say it so often to any of the pupils that I teach “the thumb pulp in hand based jams (whether thin, paddle, perfect or cupped hand) is your friend, and you must use it effectively”

Happy jamming,