How to Self Arrest with an Ice Axe: This Could Save Your Life!

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Self arrest keeps us safe. It’s the snow-climber’s and snow-hiker’s last means of protection and self-preservation. Like the airbag in our car, it’s there for when the crumple zones fail and seatbelts go slack.

Have I ever had to self-arrest? Yeah, but not in the “looks like an action-adventure movie” sort of way that makes for a good story and an even better visual.

All of my self-arrests came from taking small slips on low-angled terrain (about 30 to 35 degrees). One was because I hit some hard, alpine ice underneath some sugar snow, and the compacted snow between my boot and the ice kept me from getting very good traction with my crampons. One was - similarly - a slip when a bunch of wet, heavy snow had balled up and stuck to my crampons and kept my spikes from reaching the surface and engaging when I took my next step.

The reasons these self-arrests didn’t become very note worthy is because I was well practiced, and I arrested very early in my slide. Almost instantly. So, they looked more like: feet come out, I get onto my chest (because I am weighting my chest over the pick of my axe), I slide a few feet, and come to a stop. It looks almost like an uncoordinated pratfall from a bad romantic comedy than some epic alpine maneuver from the latest spy film.

But that’s the point. You have to have this stuff trained into your muscle memory so that you can just react without thinking. The time lapse to your reaction is a very important factor.

In the video, I mentioned that, on a 45 degree slope, I need to exert about 225% more force to stop my slide after three seconds than I would have to after one second. I promised to lay out the figures, a bit. So, here it is:

In a free fall, you are gaining speed at 9 meters per second per second. So, using rounded figures just to make the point, that means that after 1 second of fall, you’d be going about 10 m/s. After two seconds, that’s 20 m/s, and after three seconds, that’s 30 m/s.

Well, let’s now think about momentum. Momentum equals mass times velocity. I weigh about 140 lbs. Let’s throw in the weight of a backpack and my clothing, and all that; so, let’s call it about 155lbs, or 70 kilograms.

That means that after one second of fall, I am producing 700 kg*m/s of momentum. After two seconds, that 1400 kg*m/s, and 2100 kg*m/s.

So, I need to produce 300% more force to overcome the momentum of my fall after three seconds than I do at the one second mark… in a free fall.

But I’m not in a free fall; I haven’t accounted for the slope of the incline. on a 45 degree incline with a zero friction surface, I’m still getting almost 7 m/s/s acceleration (as opposed to the 9 m/s/s of acceleration in a free fall.

Okay, but what about the friction? There’s got to be some significant friction, right!? But here is the surprise: snow is a pretty low friction surface, with a friction coefficient of only about 0.03. So, at 45 degrees of incline, on snow, you are still getting over 6.7 m/s/s of acceleration, or about 75% of the same acceleration rate as you would in free fall.

75% of that (roughly) 300% additional force needed in my freefall scenario is 225% additional force.

The rub is that with these acceleration rates that are very near free fall acceleration, the momentum adds up so fast that you have to stop the fall before you really get going. So, if you get more than a handful of seconds into your snow slide, it may already be too late to arrest.

That’s where the muscle memory and the goofy looking-, comical slip- type of self-arrests come into play. They are the only type that work. Forget the movie versions.

So, how do you get that muscle memory so that you can have those needed reflexes? Practice: every year as the snow season comes around; when you see a safe slope (meaning gentle and with a good “runout”: no rocks, trees, or other objects to run into should you fail to stop) and are ahead of schedule on a day hike; with your climbing team before a big objective.

As I mentioned in the video, you are probably going to want to tape your adze or get a pick guard. For those of you are interested, we use the Black Diamond Axe Protector and just cinch the elastic straps way tight so that the pick end of the protector is snugged up against the shaft. This leaves the axe’s pick clear to be used for practice while keeping the adze well cushioned.

I also mentioned a helmet. If you are a climber, mountaineer, or alpinist of any sort, you already have one. If you are a hiker, just know that you can borrow or rent one for practice. REI rents helmets, as an example.

And if you want my particular endorsement for a non-technical axe for snow walking and low-angled mountaineering, I like my The Camp USA Corsa Alpine.

Those three items, waterproof clothes, a snow slope that kids would be willing to sled on, and a desire to get really good at this… that’s what you need to up your safety margin in the snow covered hills the way airbags improved the safety margin in cars.