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.

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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.

    Parking sign re-design

    I’ll be the first to admit that I experience cognitive overload while trying to park. When there are three signs and the information needs to be combined across them, or at least each one needs to be searched, considered, and eliminated, I spend a lot of time blocking the street trying to decide if I can park.

    For example, there might be a sign that says “No parking school zone 7-9am and 2-4pm” combined with a “2 hour parking only without residential permit 7am-5pm” and “< —-Parking” to indicate the side of the sign that’s open. It’s a challenge to figure out where and how long I can park at 1pm or what happens at 7pm.

    Designer Nikki Sylianteng created new signs for parking in Los Angeles that incorporated all information into a single graphic.

    http://nikkisylianteng.com/project/parking-sign-redesign/
    http://nikkisylianteng.com/project/parking-sign-redesign/

    I still have some difficulty in going back and forth to the legend at the bottom, but probably just because I’ve never seen the signs before. Otherwise, one just needs to know the time and day of the week.

    An interview with her can be found in the LA Weekly where she describes mocking up a laminated example in NY and asking people for feedback on the street via sharpies. (Yay for paper prototypes!) An NPR story focused on the negative reactions of a few harried LA denizens, who predictably said “I like how it was,” but I’d like to see some timed tests of interpreting if it’s ok to park. I’d also like to suggest using a dual-task paradigm to put parkers under the same cognitive load in the lab as they might experience on the street.

    As for NY parking signs – I still can’t parse them.

    The Square Cash Disappearing Act

    Square Cash is a great service – it allows you to send money via an email with no service charge if you’re using your debit card. You can receive money without entering a PIN. I use it all the time to divide up restaurant bills among my friends. That said, I found a usability issue yesterday that I wanted to share.

    I needed to link my debit card to the app, so I followed their very simple instructions for entry. 

    The first screen asks for the card number. The number pad is telephone-order rather than number pad-order. This is on a phone, so that makes sense even if I’m much more used to entering these numbers using a keyboard.

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    Next, the expiration date. On my card, the expiration date is 09/16/2016*, so I start to enter it.

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    Here is the screen as you start to enter the date:
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    I then proceeded to enter 09/16 as I looked at my card, then the CCV, and got an error message about an incorrect card number. Tried again. Same. Did this four times before I realized that the expiration date was month/year. It isn’t as though I’d never seen this, or been asked to enter just the month and year from a card, so I thought hard about what tricked me.

    I concluded it was the difference between the second and third screens – the guidance is there before you start typing, but as soon as you put in any number for the date, the guidance disappears. Since I was looking down at my card, I just entered what I saw and didn’t think enough to check – especially since it called for ##/##, which matched the month and day on my card, not ##/####, which could only be a month and year.

    You are welcome to blame the user for this one, but it would be a small fix to keep the background guide visible during entry.

    *No, I’m not dumb enough to put my real card number or expiration date in the pictures for this post. :-)

    Short Course in Anthropometry

    NPR just ran an extremely detailed article on the importance and study of anthropometry. The topic is the undue stress nursing places on the spine, even when “proper” lifting procedures are followed. Highlighed is the work of Bill Marras (recent Editor of the journal Human Factors), who developed a sensor rig for the forces experienced by the spine. Read for yourself, but if you want the high points:

    “Moving and lifting patients manually is dangerous even for veteran nursing staff, Marras says, for several reasons:

    • The laws of physics dictate that it’s easiest to lift something when it’s close to your body. But nursing employees have to stand at the side of the bed, relatively far from the patient.

    • Nursing employees also often bend over the patient. That’s important, because there’s a chain of bones along the spine, called facet joints, hidden under the little bumps protruding under the skin. Those bones interconnect and help absorb loads when standing straight. Marras says that when nurses lift as they’re bending, those bones disengage and their disks take most of the force. Those forces are “much, much higher than what you’d expect in an assembly line worker,” he says.

    • When nurses keep working under these loads, it causes microscopic tears in the “end plates,” which are films as thin as credit cards above and below each disc. Those tears lead to scar tissue, which can block the flow of nutrients into the disks — until, eventually, the disks start to collapse. “You could be doing this damage [to your back] for weeks or months or years, and never realize it,” says Marras. “The event that caused you to feel the problem is just the straw that broke the camel’s back.”

    The final conclusion was that people cannot lift other people safely. Assistive machines are needed, and as the article points out, hospitals do not have them.

    Treemap sighting in the wild: U.S. Budget proposal

    imageI get pretty excited when I see my favorite infovis being used: The Treemap

    Just released today – the proposed U.S. budget as a treemap!

    So, how well did this visualization work for its intended purpose:

    • Points awarded for using a treemap – it makes it so easy to see how massive social security and healthcare are.
    • Points deducted for the cluttered overlay text in the Transportation section.
    • Points deducted for making the areas clickable, but not actually providing more information beyond a platitude (“Military Personnel: When it comes to our service members and their families, America stands united in support. The budget helps ensure that those who serve our country receive all the support and opportunities they’ve earned and deserve.”)
    • Points deducted for making me click a link to “learn more” from a YouTube video of the entire State of the Union address when I could be learning more with a deeper treemap.

    I’d like to see more of the blocks broken down into the components they fund, making it as informative and transparent as my go-to example of a treemap: the stock market. My second favorite treemap is a program that will treemap your harddrive, making it easy to see where those giant spacehogging files are hiding, deep in directories you forgot were there. I treemapped my lab server with it as we ran out of space and found giant video files about 10 directories down in an unlikely spot that were eating up our GBs.

    Perhaps we could have a treemap that lets us change things in the budget to see how we would make it look, like the American Public Media interactive “Budget Hero” game from a few years ago (now defunct or I would link it)? I learned a LOT about what could budge and what couldn’t budge in the budget from that game.

    *All the points deducted are far outweighed by my support of the treemap being used in the first place! Brilliant!

    Nonagenarian designs for aging and inspires younger designers

    Barbara Beskind, 90, is a designer at IDEO who works with engineers on products that improve the quality of life for older people. Nicolas Zurcher/Courtesy of IDEO
    Barbara Beskind, 90, is a designer at IDEO who works with engineers on products that improve the quality of life for older people.
    Nicolas Zurcher/Courtesy of IDEO

    NPR published a great story on Barbara Beskind, a product and interface designer in her early nineties.

    My favorite excerpt:

    Gretchen Addi, an associate partner at IDEO, hired Beskind. Addi says when Beskind is in a room, young designers do think differently. For example, Addi says IDEO is working with a Japanese company on glasses to replace bifocals. With a simple hand gesture, the glasses will turn from the farsighted prescription to the nearsighted one.

    Initially, the designers wanted to put small changeable batteries in the new glasses. Beskind pointed out to them that old fingers are not that nimble.

    “It really caused the design team to reflect,” Addi says. They realized they could design the glasses in a way that avoided the battery problem. “Maybe it’s just a USB connection. Are there ways that we can think about this differently?”

    There are several wonderful take-home messages:

    • Creative and fulfilling work can extend late into the lifetime
    • Aging does not just bring limitations, it also extends perspective and wisdom
    • Designing for aging is doesn’t detract from a product but can enhance it for people of all ages
    • Having a person with such perspective on a design team changes the perspective and thoughts of the rest of the team, the core tenant of participatory design

    Apple Watch Human Factors

    watchThe big news in tech last week was the unveiling of the Apple Watch. I think it is a nice moment to discuss a range of human factors topics. (This topic may elicit strong feelings for or against Apple or the idea of a smartwatch but let’s keep it about the science.)

    The first is technology adoption/acceptance. Lots of people were probably scratching their heads asking, “who wears a watch, nowadays?” But you do see lots of people wearing fitness bands. Superficially, that contrast seems to demonstrate the Technology Acceptance Model (TAM) in action.  TAM is a way to try to understand when people will adopt new technology. It boils down the essential factors to usability (does it seem easy to use?) and usefulness (does it seem like it will help my work or life?).

    Fitness bands check both of the above boxes: since they are essentially single-function devices they are relatively easy to use and tracking fitness is perceived as useful for many people.

    Back to the Watch, it may also check off both of the above boxes: it certainly appears easy to use (but we do not know yet), and because it has fitness tracking functions plus many others via apps it certainly may be perceived as useful to the same crowd that buys fitness bands.

    The next topic that got me excited was the discussion of the so-called digital crown (shown below). Anne and I have previously studied the contrasts between touch screens and rotary knobs for a variety of computing tasks. Having both choices allows the user select the best input device for the task: touch for pushing big on-screen buttons and large-scale movement and knob for precise, linear movement without obscuring the screen. Using a knob is certainly easier than a touch screen if you have shaky hands or are riding a bumpy cab.

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    Two small items of note that were included in the Watch was the use of the two-finger gesture on the watch face to send a heart beat to another user–the same gesture many people intuitively think of when they want to feel their own heart beat.

    Finally, the Watch has the ability to send animated emoij to other users. What was noteworthy is the ability to manipulate both eyes and mouth in emoji characters. I couldn’t find any literature but I recall somewhere that there is some cross-cultural differences in how people use and interpret emoji: Western users tend to focus on the mouth while Eastern users tend to focus on the eyes (if you know what reference I’m talking about or if I’m mis-remembering, feel free to comment).

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    There’s so much I haven’t brought up (haptic and multi-modal feedback, user interface design, automation, voice input and of course privacy)!

     

     

    Not blaming the user since 2007!

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