Rock Climbing Human Factors – Harness attachment points

A friend of mine was recently rappelling from a climb, meaning that she had the rope through a device that was connected to her belay loop on her harness. As she rappelled, she yelled that her harness broke, and the waistband of the harness slid nearly to her armpits. Fortunately, she remained calm and collected, and was still able to rappell safely, if awkwardly, to the ground. On the ground, her partner saw that her waistband with belay loop had become disconnected from her leg loops. The leg loops were intact, though a keeper-strap that helps the leg loops stay centered was no longer connected.

So, what happened?

First, for the non-climbers, a primer. A climbing harness is composed of three major parts, attached to each other in various ways depending on the manufacturer. The first part is the waistband, which is load-bearing, meaning that it is meant to take the weight of a climber.

The second part of the harness is the belay loop, a load-bearing stitched circle that connects the waistband and leg loops and is also used to hold a belay device, to hold the climber’s weight when rappelling, and for anchoring to the ground or a wall when needed.

The last part of the harness is the leg loops, which are also load-bearing in the parts that connect to the belay loop and around the legs themselves.

Figure 1 shows the general composition of climbing harnesses, with these three parts diagrammed in the Base Concept.

harness_leg_loop_error
Figure 1. Simplified diagrams of climbing harnesses.

On most harnesses, the leg loops are kept connected to the belay loop by a “keeper strap.” This is usually a weak connection not meant to bear weight, but only to keep the leg loops centered on the harness (shown in blue in figure 1). In the case study that prompted this blog post, the keeper strap was connected through the belay loop, rather than the full-strength leg loops (figure 2.) When loaded, it came apart, separating the leg loops from the waistbelt. My own tests found that the keeper strap can be very strong, when it is loaded on the strap itself. But if the leg loops move so that the keeper buckle is loaded by the belay loop, it comes apart easily.

errorharness
Figure 2. Harness assembled with keeper strap bearing weight via the belay loop.

There are two ways to mis-attach leg loops to the belay loop of a harness. The first way is by connecting the leg loops back to the harness, after they were removed, using the keeper strap. The video below demonstrates this possibility. Once connected, the harness fits well and gives little indication the leg loops are not actually connected to bear weight.

The second (and I think more likely) way is by having the leg loops disconnected from the back of the harness, usually for a bathroom break or to get in and out of the harness. The leg loops are still connected in the front of the harness, but if a leg loop passes through the belay loop, suddenly the keeper strap is load bearing when the leg loops flip around. However, the harness does not fit differently nor does it look particularly different unless carefully inspected. Video below.

The non-load bearing parts of the harness are what determine the possibility for this error. In figure 1, some harnesses either do not allow disconnection of the leg loops in back or only allow their disconnection in tandem. When the leg loops are connected in this way, the front of the leg loops cannot be passed through the belay loop. Video demonstration below.

Back to figure 1, some harnesses allow the disconnection of leg loops for each leg. If these are disconnected, a loop may be passed through the front belay loop, resulting in the error in figure 2.

In sum, this error can be examined for likelihood and severity. It is not likely that the error occurs, however if it does occur it is likely it will go undiscovered until the keeper strap comes apart. For severity, the error could be lethal, although that is not likely. The waistbelt will hold the climber’s weight and having leg loops and a waistbelt is a (comfortable) redundancy. However, the sudden shock of suddenly losing support from the leg loops could cause loss of control, either for an un-backed-up rappell or while belaying another climber.

What are the alternatives?

  • Climbing is exploding, particularly climbing in gyms. The “gym” harnesses, with fewer components and gear loops (Figure 1), are a good option for most climbers now. However, there is little guidance about what harness one should buy for the gym vs. outdoor versatility so few probably know this harness is a good option.
  • Some harnesses are designed to be load-bearing at all points (i.e., “SafeTech” below). It is impossible to make an error in leg loop attachment.
  • safetech

  • Harnesses with permanently attached leg loops or loops that attach in the back with a single point are unlikely to result in the error.
  • Many climbers reading this are thinking “This would never happen to me” or “You’d have to be an idiot to put your harness together like that” or my usual favorite “If you wanted climbing to be perfectly safe, you shouldn’t even go.” Blaming the victim gives us a feeling of control over our own safety. However, there are other instances where gear was assembled or re-assembled incorrectly with tragic consequences. No one (or their child) deserves to pay with their life for a simple mistake that can be prevented through good design.

    5 thoughts on “Rock Climbing Human Factors – Harness attachment points”

    1. This is a very nice post, both clear and detailed. In addition to the failure mode you show, where the load is more heavily on one leg, this failure is very likely during rappelling. The reason is that the cyclic load in rappelling (the “bouncing” one feels if the rappel is not completely smooth) tends to cause webbing to “walk” through buckles. This is a large part of the reason that standard non-locking buckles must be doubled back to be safe. Of course, doubling back the buckle on the keeper loop would not solve the problem because that loop is still not load-rated.

      Luke

    2. If the harness maker wants to keep the removable leg loop feature rather than sealing it off via a full strength keeper, another design-side solution would be to use different color webbing for the keeper, like bright orange. This is already something Arc’teryx does inside their belay loops to indicate wear. It’d be an easy and cheap solution.

    3. Timely…almost!

      Last semester, I taught a human factors class. As part of the class, we had a couple field trips. The first field trip was to Burger King where we had a manager give us an in-depth look at the Coke Freestyle dispensing system. (Pepsi also has one, the Inspire, but it is not in our market yet.)

      The second field trip started with an experienced rock climber who took us to the campus rock wall and explained the equipment and climbing techniques. Then we went back to the classroom where he gave a presentation with analysis of human factors and climbing accidents. We used the HFACS process (The Human Factors Analysis and Classification System (HFACS) was developed by Dr Scott Shappell and Dr Doug Wiegmann) throughout the semester as each student presented an analysis of the “Crash of the Week”. The students then applied the HFACS process to the accidents that were presented. This made lively discussion.

      Even though the semester is over, I will be sending the link to this blog entry to my [former] students and our guest speaker.

      Thanks for a great post!

    4. Very nice post. I just wanted to jump in here as well.

      Misty Mountain stopped making the removable leg loop feature in roughly 2013 specifically for the reasons stated in this excellent blog post. The Big Wall Harness, Titan, where it is nice to remove the leg loops for extended stays on a big wall does still have this feature but may undergo a redesign without it in the near future.

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