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What Is Suspension Trauma a.k.a. Harness Hang Syndrome? (dynamicrescue.com)
141 points by mhb 36 days ago | hide | past | web | favorite | 136 comments

A similar root cause issue is developing life threatening blood clots from sitting too long. Both suspension trauma and blood clots in the legs come from a clever optimization of our circulatory system. The heart can't actually pump blood out of the legs. It counts on muscle activity to make the flow happen.

If you sit for many hours, like on a cross country or cross ocean flight, or because you are a dev or gamer with tremendous concentration and focus, the blood quite literally just sits in your legs and eventually starts to coagulate. It doesn't matter how much exercise you get the rest of your day, those 6 or 8 hours of sitting can quite literally kill you through the creation of a blood clot that then flows through your system and blocks blood flow to the heart or brain (all learned personally when I developed such a clot from routinely sitting long hours in a coffee shop with my laptop and 100% focus).

If you're like me and can focus easily for many hours straight, get a Fitbit, turn on activity tracking, and when it tells you you haven't walked around recently get up and walk around. It's much less impactful to your concentration than an emergency ER visit followed by a lifetime of prescription blood thinners to reduce the now much higher risk of a second clot.

I also learned this the hard way after a 14 hour session of Diablo 3. I went to the doctor a couple of times because my leg felt swolen and it was hurting but they didn't think much of it for some reason - only after I developed extreme difficulty breathing did I end up in the ER. The DVT had migrated from my leg into my lungs and gave me a pulmonary embolism.

What a terrible game to almost die for. I'm so sorry.

Also, 14 consecutive hours? Did you literally not get up at all in that period? Did you have enough fluids and snacks nearby that you didn't have to?

It was consecutive but I did get up from time to time for bathroom breaks, but clearly not often enough. As for fluids I'm fairly sure I was pretty dehydrated at the time. This occurred in 2015. Since this occurred and after I learned from a nurse about the leg muscles being critical to get the blood moving out of your legs I have developed a habit of constantly moving my legs around any time they have not moved in a bit. When this episode happened I remember that I would keep my legs very still during the gaming session.

You're lucky to be alive. Pulmonary embolisms are often fatal.

That’s a common misconception.

Most are clinically silent. The ones that land you in an emergency room are dangerous.

Yeah, I suppose.

A few years back, I was blinded in one eye by a retinal vein occlusion (basically a stroke in the retina). They're actually pretty common, affecting 5-10% of the population, but unless it crosses your macula, you'll probably never know it happened.

I recently suffered an occular migraine. My first and only (so far). Scariest moment of the decade for me. Thought I was going blind, thought I'd have to adjust to this new normal. Got myself to the ER just in time for it to clear out.

Eye issues terrify me and I'm not sure mental state could handle a retinal stroke. That sounds truly horrible.

I've had ocular migraines my whole life, as long as I can remember (I clearly remember them happening before kindergarten, and was seeing doctors when I was six). Luckily, they've gotten far less common and intense as I've gotten older... they were completely debilitating during my early teens.

Is it curable? Has your eyesight been restored?

It's treatable, not curable. Treatment lasted about a year, consisting of monthly injections into my eyeball (yeah), and a laser surgery that cauterized about 50 tiny veins. I have a blind spot and some unevenness, but it's usable. My bad eye is better than many people's good eye. It's about 20/40-20/80 now, depending (my good eye is 20/20).

Hooray for modern medicine! It saved my eye. When the occlusion first happened, my vision went from 20/20 to 20/500 in moments.

If "Clinically silent" is jargon for "no symptoms at all", sure.

But if it gets the point of even minor persistent chest pain or one is aware that something is not right, it's time for the emergency room.

Chest pain is not to be trifled with. One clot may be followed by others which might be serious or fatal in a very short time.

PE is common enough among people that sit for a living (most of HN), that I think it's important for folks to be aware of them and that they're dangerous.

I've had mild chest pain for years. I'm not going to live in the ER.

Do you know if the chair you sat on was impinging the back of your upper thigh? Do you have any health risks associated with DVT e.g. Smoker, use birth control, overweight, etc.

Any family history? Crazy how this happened from one 14 hour session or were you regularly doing this?


When it happens, it will result from one session. Whether it happens in any given session is a statistical question.

"Deep Vein Thrombosis" is the term if anyone is looking for more info. https://www.cdc.gov/ncbddd/dvt/travel.html

Yep, flew from Phoenix to Atlanta, fell asleep until the end of the flight, woke to get off the flight, and immediately became blind in one eye as an embolism blew up inside the vitreous fluid.

Not a great way to start a new job. Boss was meeting me at the airport thankfully and he drove me to the hospital to get checked out. A few weeks of an eye patch was the short term outcome and a bunch of new 'floaters' that my mind has mostly learned to filter out.

Just very grateful that it detonated in my eye instead of my brain...

The link I posted mentions it's not just air travel, but car, train, bus, etc, also.

But I have to wonder if the shrinking coach seat pitch/size isn't a big factor. I'm fairly average size, but flying is miserable these days.

Perhaps also the relative awkwardness of getting up while flying...the visible sighs from your row mates that have to move around a lot to let you pass.

That's a fluke. PHX to ATL is only 3.5 hours. If sitting still for that long easily led to blood clots, people would be dying in droves.

I imagine sleeping is part of it though, when you're asleep your heart beats even slower than when awake.

Woah, I will fly from Atlanta to Germany soon.

Now I'm scared..

Wear compression stockings from ankle to thigh and pop an aspirin to thin your blood an hour before flight. These helped me as I'm at high risk.

Just get up and walk around every hour or two...

"just" is not the word to associate with "get up and walk around" on an airplane. Unless you have an aisle seat it's a notable hassle.

No, it's not. You say "pardon me" to your seat mate and they let you out or you climb over them.

That is the description of the hassle (skipping the parts where they are asleep, have drinks/food/laptops, etc). But if you feel better for denying any social anxiety or physical discomfort I or others feel while "climbing over" strangers periodically, don't let me stop you.

Aisle seats make up at least a third of all seats and don’t cost extra.

And they are my preference. But they aren't always available - per this topic, you're saying 2/3 of people have a harder time (despite the dismissive commentary from others) performing a routine task for their health.

It’s not a solution for the masses, but it works well for the individual.

Nah, screw your seatmates. If they didn't want to have to wake up every two hours they should have taken a window seat.

Even with that approach, I’m not sure there’s enough room for everyone to take the recommended stand breaks.

Thank you for your comment. I hadn't paid any attention to why sitting was bad for your health, I thought that my daily routine of exercise was sufficient to take care of this issue. Now that your comment has explained this really clearly - that it's the prolonged hours of the inactivity of the legs that's the issue, I will definitely make it a point to get up and move around more frequently. I can and have just sat at my desk for stretches as long as 4-5 hours just concentrating on code routinely. Your comment may have saved me from my work habits contributing to an early demise :-)

Does furiously bobbing one’s knee prevent this at all?

Been wondering the same thing: What manners of muscle movement work for circulating the blood?

According to (1) blood flow maximizes around 30% of max effort. So light contractions seem best.

1: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4591373/

I'm certainly not a medical professional, but my impression is that it's not so much movement as muscle tension that helps. If the muscle just moves without encountering any resistance, it doesn't create nearly as much pressure as it does when e.g. walking. So you really need to have weight or some other sort of resistance against the motion. I try to wedge my feet against something and use my calves to lift myself off the seat.

Maybe someone who actually knows can tell me whether I'm totally off-base here?

From the article, it says that contraction of the muscles pushes against the veins. Given that, the less resistance the better. You don't need the muscles to work harder, you just need them to be maximally shortened.

In other words, what you should really do is flail around wildly. As a bonus, this also slightly increases the heartrate of nearby coworkers.

You have to flex your calves to pump the veins deep in your legs, you can do seated calf raises. Standing up and walking around is ideal.

Article said movement helps, but the victim usually gets tired of it.

Or someone else does and insists they stop fidgeting and keep their legs still.

There is a theory that pregnant women sleeping on their backs can have serious complications due to a venous return being obstructed. Some get supine hypotension, and others get restless or sore legs. There appears to be an an atomic variation in venous anatomy, where some women can get return via the azygus vein if the inferior vena cava is compressed.

This is very relevant for HN. Most devs need to be aware of how dangerous sitting down for too long really is.

That's just the tip. Even casual reading through Wikipedia shows that like a half of health functions are tied to muscle work. E.g. anti-inflammatory function, because muscles act as endocrinal organs.

The interdependencies in this bag of organs are an unbelievable mess.

Refactoring is not an option, we don't have root access to production. We can either exploit bugs or deploy new versions.

Those new versions are creating by randomly selecting between files from two other installations.

>The interdependencies in this bag of organs are an unbelievable mess.

I choose to look at it as incredible optimization instead.

Smoking is a high risk associated with DVT as well, quitting smoking is also ideal to reduce risk

So true. Be aware that you may have no symptoms in your legs at all, and still develop pulmonary embolisms.

As an otherwise healthy and fit adult male, my first symptom of my PE was a sharp stabbing pain in my chest when inhaling. Thinking I was having a heart attack, I self-admitted to the ER. I had 12 PEs in my lungs, and with ultrasound they found a 3" long deep vein thrombosis under my left knee. My left leg had absolutely no symptoms or pain. My PEs and DVT resolved with a 6-mo course of blood thinners, but I was lucky. PE mortality rate is around 15-20%.

Set your "stand up" timer for every 90 minutes and actually pay attention to it! And it wouldn't hurt to take a daily baby aspirin (probably should ask your doc first).

> And it wouldn't hurt to take a daily baby aspirin (probably should ask your doc first).

This is a really interesting point.

Most people have probably seen the debate around daily aspirin, which largely simplifies to "does the decreased clot risk outweigh the increased bleeding event risk?" The math tends to come out very close, but that's largely because the people at high risk of heart attack and stroke are also at elevated risk of bleeding events.

Programmers, heavy gamers, and other people who sit all day seem like they might break that parity; the raised clot risk is circumstantial, not biological, so they're not necessarily at elevated bleeding risk. Changing that circumstance is definitely the winning move, but I'd also love to see a study on how aspirin performs in those populations.

The American Heart Association now recommends against daily aspirin use for most people.


I am haunted by DVT that took the life of a best friend who had a pulmonary embolism in her sleep and never woke up. I now take asprin regularly when I have to sit for prolonged hours. Stay safe everyone.

My former team lead had one of those standing desks. After he left, I toyed with the idea of using it. When the office moved, I decided to take it. It's pretty useful to keep me awake in the afternoons.

I've found there's another afternoon benefit. If I'm standing in the afternoons and struggling to stay awake, that's a really good push to take a short nap.

When I'm sitting in the afternoons it's easier to push myself and skip the nap, which actually results in worse productivity and me feeling worse the rest of the day. It's harder to skip a nap with a standing desk because it's harder to tolerate being sleepy when standing.

YMMV based on if afternoon power naps work for you or not.

Does your workplace have accommodations for taking a nap?

Right now I work from home most days so yes :)

In the past I've napped in my car. At one job they had a "multicultural room" that was basically an interior room with a comfortable chair. At another job (a startup that was collapsing) there was a couch in a vacant office on the same floor.

Note that I've many places did not provide standing desks.

I bet restless feet help a lot in preventing this, too.

I'm not sure why that's being dismissed. Standard advice for travelers to avoid thrombosis recommends leg exercises during extended sitting, including both toe and heel raises. "Shaking your legs" while sitting generally consists of either tapping your toes or bouncing your heels; heel raises in particular really are the same motion as fidgeting.

I wonder if standing desks can be just as dangerous as sitting if you are standing motionless for more than an hour or so.

I'd say it's much harder to stay perfectly motionless while standing than while sitting. Subtle shifts of weight from one leg to the other are enough to stave off DVT.

If you don't want to buy a FitBit, Workrave[0] is great computer software for this. Runs on Windows and GNU/Linux.

I know I should take breaks, but never end up doing so - the desire to just keep sitting and working is too great. The reminders from Workrave have been effective at actually getting me to stand up and move around.

The only issue is that if you are sitting at your desk but not using the computer, it will detect you as taking a break.

[0]: http://www.workrave.org/

Second the fitbit tip! Aside from not dying prematurely, you'll also enjoy increased energy and focus (assuming you actually do get up and walk around every hour) and, at least in my experience, you'll feel better at the end of the day. Just the few minutes of walking every hour makes the difference between a sore and achy back and comfort. Sleeping is easier, too.

I have privacy concerns with fitness trackers, so I did a search and found this: https://github.com/Freeyourgadget/Gadgetbridge

Seems very interesting, if this project is any good (certainly looks like it is) I may just get one of the supported devices.

Back in 2013 or so, I had privacy concerns, so I got a device that was popular for folks that wanted to put free software on it. Hacking on it (both for fun, as well as frequent buggy behavior) served to keep me at the desk instead of working out :(

You should stop using HN. I can tell that 4 hours ago you were awake, using your computer, not taking steps. Are you really comfortable with this loss of privacy?

The best thing I ever did for myself recently was getting a Swiss ball as a seating implement. It fixed my posture and every so often I can just bounce "locally" to unwind and get blood going. Good thing nobody can see me acting weird at home.

Plus as the ability to slouch is gone, I've got no incentive to stay seated and get up more often.

My manager sits on one at work. He also rolls it around the office as he goes to meetings, etc. Nobody thinks he's acting weird, and recently I saw that someone else had brought one in.

When I got an Apple Watch I quickly learned that for me the hardest ring to close was to stand up at least once in the hour for 12 hours in the day. Now it has become habit, but it's something I never really noticed since I went to the gym every day and am generally healthy.

Could standing for too long also result in blood clots? Gravity is going to keep more blood in your feet. Am I gonna have to start doing regular squats at work?

The people that I know who have to scrub into a long surgery in the OR typically wear compression socks as they may need to stand for 9+ hours straight.

If you want to do squats go for it, but compression socks are passive & much harder to forget doing.

If you are sitting down for lunch & meetings during your work day it's probably not as much of a big deal.

So you sacrifice your privacy to buy a device that tells you to get away from another device?

I don't understand this way of solving problems.

What's not to understand? Op uses a Fitbit to keep track of how much time they spend sitting to help avoid injury.

Not sure how devices or privacy have anything to do with the problem.

That's what I don't understand. Devices are the problem. You're solving one problem and creating several more.

When you could just set an alarm on your computer to get up and walk around in and hour or two.

I'm a #FitbitEmployee but don't speak for Fitbit.

The advantage of the device is that it doesn't interrupt you if you've already taken 250 steps that hour.

I take it you own a smartphone based on this previous comment: https://news.ycombinator.com/item?id=19688327

Even if you don't own a smartphone, the loss of privacy to Fitbit is minimal, in my personal opinion. If you do own a smartphone, adding a Fitbit to the picture means an infinitesimal loss of privacy, too small to even be worth talking about. Fitbit has a financial incentive to keep your data private. Can you say that about every app on your phone?

When this phone dies I probably won't get another one. Someone gave me their old cracked phone. It would otherwise be garbage and I won't buy a new phone because the whole system is killing the planet and human beings in places we can't name.

It's so gross, I don't want to be part of it anymore.

So I think you're not going to change my mind about this.

Until we start saying no this can't happen anymore. It will keep on.

We are all culpable.

Sitting for too long is the problem not devices. I agree a timer would probably work just as well, but the number of devices has nothing to do with fixing the problem of sitting too much (especially a device intended to help increase physical activity).

I am currently building a house, and there are large portions of it that have a >25ft drop from rooftop to the ground below. That means the workers on the roof or upper floor need to wear proper fall protection. Depending on the job that can often by a harness system.

I was surprised that because of the height of the potential fall, we needed a "rescue plan". In other words: arresting the fall is only half the job.

The result was quite a bit of extra expense for us (because of the site conditions, we need to keep a hydraulic lift available), but when I read about how quickly suspension trauma becomes an issue, I could understand why the safety regulations are written as they are.

It's always surprising to me how fall risks operate in the world of OSHA compared to rock climbing. There's an entire domain where people take good-sized falls as an everyday event, just sort of sitting in parallel with the domain where they're considered a major risk needing emergency-response measures.

Obviously, some of that is a real difference in situation. Construction falls are unplanned and happen under all sorts of odd circumstances, and people are quite often injured during their falls. Climbers have someone managing the other end of their rope at all times, on a system that makes lowering them to the ground straightforward.

But other differences seem absolutely pointless. The "suspended by your groin, legs hanging straight down" posture of construction harnesses massively accelerates suspension trauma, while climbing harnesses pull the legs up and keep pressure on large muscles. And there are companies starting to use that design for safety gear, so it's not a regulatory issue - it just somehow took decades to cross the gap.

As a fellow climber, a first-time(but long-time climbing veteran) lead climb partner taught me a valuable lesson about this: Always carry an ascender, even if it's not for you.

They are inexpensive, and the 10 seconds you spend feeding it above your harness can save your life. Tying a prusik is easy, and you should be able to do it in your sleep before even thinking about lead climbing outside of a gym. However...tying a Prusik with a fractured arm and bleeding head after a 15-50 foot lead climbing fall before you smack against the face is less-than-easy. In those situations, being able to grab the ascender with whichever hand/arm is not fractured, is far easier than starting a Prusik.

I big difference between a climbing harness and a construction harness is the tie in point. Climbing it is fine to have that point in front of the user. For construction, having the rope constantly in front of you would be a real inconvenience. By tying in on the back, the harness will hold the user in a different orientation just due to the way weight is distributed.

That's definitely part of it; climbing harnesses tend to support you in a position that's great for suspension trauma, but involves a pretty inconvenient rope. They're also waist-and-hip only, and while they'll reliably hold a climber through a flip, it doesn't sound great for chaotic, confined-space falls where you might stay upside down.

The newer generation of construction harnesses are still back-clipped and full-body though - a short strap runs from the waist to the back clip to redistribute weight without normally being in front of you. Presumably getting that working smoothly and safely was an extra engineering hurdle, but I'm still surprised harnesses went so long without even including waistbands.

It's partially a quirk of OSHA, and possibly a temporary one. Analogous safety standards in Europe, I'm told, allow for either the dorsal or sternal D to be used for fall arrest.

That's why you would never catch me on a rope without at least a pair of loops of smaller diameter rope that I could tie into Prusik knots and self-rescue. Those pieces of rope are almost weightless. There's no reason not to have a pair with you when you get on rope.

Featured in a James Bond stunt:


(The clip is from "For Your Eyes Only" but has music from some other bond film dubbed over it)

Wow, apparently you can pull yourself up by your own bootstraps!

Try getting a prusik system set up when your tie in point is in the middle of your back as most construction harnesses are set up. It makes it much harder to self rescue.

Side note, one of my favorite ways to get up a rope when hanging in free space is to walk the rope. https://www.youtube.com/watch?v=gAzXYVdskFE

Also, in those times when you need a prusik, there is a less-than-tiny chance you are hurt. EG: you're trying to place your cam, and instead you take a 40 foot drop before your last cam arrests your fall by sending your body directly into the face. Prusiks are more difficult to tie(and ascend!) when your hands are coated in your own blood, etc.

Yeah for sure, injury changes things. You see rock climbers needing rescue often enough when they could have self-rescued by a pair of Prusiks and ascending the rope. I've heard of a rock climber using an ATC (rappel device) as an ascender, by kicking off the wall and moving the rope up a few inches. They were near complete exhaustion when they got up to the top - Prusiks would have made the job so much easier. Of course a pair of ascenders/Jumars is best, but add some weight.

Most people (outside of cavers) don't plan on climbing up a rope with single rope technique, so it's not something that is practiced very much. I'm not really sure why. I'd be super nervous as a climber if I only could go one way on a rope. I guess alpinists practice it some for self-rescue out of a crevasse.

Cavers use the rope as a nylon highway, so you know how to switch from rappel to climb, climb to rappel, and how to pick-off an injured party from the rope (all of those in space, where you can't take your weight off the rope at all).

I have, thankfully, never had to try to tie a prusik with my hands covered in blood. If you had to do that, it sounds like a brutal fall.

Why not tie an Alpine Butterfly in advance? Isn't that more secure than Prusik or Klemheist? Or does it weaken the main rope too much?

Or are you saying to use a pair of Prusik knots to self rescue, by climbing the rope?

Yeah, the parent comment is talking about using a pair of Prusiks to ascend (or to at least make loops you can use to stand).

An Alpine Butterfly can't be moved, so it's not especially useful in many applications.

Yep exactly. I'm talking about a pair of Prusiks to climb the rope. Of course ascenders/Jumars are even better. :)


So when I was a kid, they made us climb a ~3 cm rope about 20 meters. With no aids, and just a padded mat for protection.

20m? That's a fatal fall...

OK, upon reflection, more like 8-10 meters. The ceiling height in the gymnasium. It was a long time ago, and what I mostly remember is the fear of falling. And the rope burns.

Falls from far less than that height can kill. If it is safe to be at 10 feet without that equipment, then it is safe to be at 1000 feet without that equipment. IMHO, the cutoff is just what the construction industry was willing to tolerate. The whole thing is a lobbyist battle between the construction industry and the safety equipment industry.

I think that at a lower height, a rescue is considered to be easier.

10 ft would still require a safety program, it just wouldn't be fall arrest, more likely prevention (scaffolding)

Wow, I had no idea this was a thing. I nearly blacked out the first (and only) time I went skydiving. Tandem jump with instructor. Free fall was fun. After parachute deployed the harness started feeling tight around my chest and legs. I got dizzy and it felt like I was having a panic attack, difficulty getting enough oxygen. When we landed I immediately fell to the ground where I couldn’t get up for a few minutes.

My friends who jumped with me were all laughing and having a great time, they thought I was being dramatic or something.

A web search brought up tons of hits of this being discussed in skydiving forums. Apparently it’s related to older harnesses. Some skydivers don’t believe it’s real.

Thanks for posting this.

Its interesting to me as a rock climber that I've never heard of this. Its not unusual for someone to hang in their harness at an anchor for quite a while while their partner is climbing the pitch before and after. Are climbing harnesses that much more comfortable than safety harnesses that its not a problem?

As a climber who saw OSHA warning sheets about this, I had the same question and found several major differences.

1. This is almost exclusive to sustained free hangs. Bouncing against a wall or otherwise working your thigh muscles circulates blood with minimal effort, so standard climbing circumstances raise the safe time - potentially by hours. (Notably, Alpine climbing guides and specifically Alpine rescue guides do cover this syndrome in case someone falls and hangs while awaiting aid.)

2. OSHA-style harnesses are over-the-shoulder devices anchored between the shoulderblades. Many don't even have waistbands, just leg and armpit straps. That's useful for unpredictable falls, but it's the worst possible configuration for suspension trauma. Your legs hang straight down and the straps pull up at the edge of your groin, cutting off blood flow. Even hanging free, the climbing harness posture (elevated legs, pressure on hamstrings) is much safer.

3. Safety harnesses are mostly cheap and ill-fitting because you're not expected to hang in them; they're the same unpadded straps you get on the worst climbing gym rental harnesses. The time to initial risk apparently varies a lot with harness fit and padding, so comfy climbing gear is also much safer.

The ad below has a good visualization of the difference; it's from a company selling OSHA-compatible harnesses which pull you into a climber-like sitting position for exactly this reason.


Safety harnesses you mention in 3 are also often for fall prevention* not fall protection. Fall protection harnesses aren't much better but typically will at least have padded leg loops.

*: Prevention: when tied in you can't make it to a place you can fall such as a system that prevents you from getting within a few feet of a roof

Edit: the link you provide seems to be a lightweight fall protection harness and certainly one I'd like using as I prefer a lighter harness when working at height because it means less fatigue and less chance of a mistake leading to a fall.

As others have mentioned, this is mostly not a problem because climbers are usually concious, and moving about and whatnot. Hanging in a harness for too long is quite uncomfortable if you don't move at least a little bit.

Where this starts to really matter though, is in the event of an accident, particularly if you're above, and belaying a second, and the second is hit by a rock or something and falls unconcious. In this case, you often can't easily lower them, especially if you're more than 60 meters off the deck; you usually can't raise them unaided either, unless you're unhumanly strong. Setting up a z-pully in a timely manner, and hauling the second up is the best option.

Unfortunatly, these sort of skills are not often practiced in the climbing community.

Edit: also, I think it's less of a practical issue in a climbing harness, unless you also have a chest harness on, or a full body, which is pretty uncommon.

Raising an unconscious climber is potentially not viable.

1. You probably don't have time. As the article says, you have less than 14 minutes. If the climber isn't within view, you may not even realise they are unconscious for a few minutes, perhaps thinking they just can't hear you.

2. If you don't have efficient pulleys, friction will be a major issue. Hauling a person up a long pitch on a Z drag is going to be a challenge. More mechanical advantage would just add more friction and time.

3. Raising the climb could cause them injury, or make their injuries worse, and could potentially kill them. Their body or the gear attached to it is likely to jam against something or snag on the way up unless it is a completely clear path.

Another option in that scenario is going down to the injured climber after escaping the belay. If you have enough rope out of the system, you can abseil down. Otherwise, you will need to descend the taut rope down to the hanging climber.

From there, I suppose you would need to manipulate their body to get blood flowing.

...and that is only the first step of the rescue! I hope I never have to face such a scenario.

It will still happen in a climbing harness if you are hanging in space. On a hanging belay, you try to get your weight off the harness and get your weight on your feet on the wall as much as possible. This alleviates the problem.

Cavers will spend a long time hanging in space on rope when climbing out of deep pits (over 100 meters / 300 ft) with single rope technique. That doesn't lead to harness hang, because you are engaged in aerobic activity with your legs.

That is true. A free hanging belay would not be very useful! I did find some discussion on mountain project about it in the context of rescuing an incapacitated climber.

Could one possible protection mechanism be to keep an ascender clipped to the back of your climbing harness, even if you don't normally use it? Then, as long as your were conscious and not too injured, you could attach it above you, and hang from it at intervals to get the weight off your legs, (while waiting for rescue) and to help with rescue?

Many climbers keep a loop of accessory cord with them to make a prusik knot for this reason. Much lighter and cheaper than an ascender but not as efficient.

At a hanging belay, one typically does not remain motionless. People move their legs around, either just while fidgeting or balancing, or bracing their legs against the rock, or aiders.

I cannot speak to any differences between climbing harnesses and safety harnesses.

There are lots of relevant differences between climbing and safety gear and posture, but you're spot on about motionlessness as the key element.

Even for safety-gear falls, suspension trauma is somewhat overhyped for "slip and your harness catches you" accidents. The natural reactions - fidget, adjust for comfort, move your legs if they feel tingly - increase the safe time a great deal, so the main risk is falling into a hard-to-recover spot and getting tired.

That said, construction incidents are far more likely than climbing falls to be worst-case events: a substantial fall paired with injury or unconsciousness. When that happens, the impact pulls the harness tight and the victim doesn't adjust it or otherwise move around at all. That's where the stats about trauma starting in minutes enter the picture.

I think the lack of movement (especially if unconscious or barely conscious) and full suspension is key. When climbing, do you typically maintain contact with the wall, especially with you feet?

Barring injury, you wouldnt be hanging in free space for very long. I didn't realize that would make such a difference.

After my comment I did some more searching and found plenty of discussion of harness hang syndrome in the context of rescuing an incapacitated climber though.

Have you read much about prusik mistakes and accidents? I feel like this is mentioned quite a bit when talking about whether to put your third hand above or below your belay device.

I think I've only heard of a single accident when this has happened and involved death, though.

(hint: put it below or you could get stuck if you can't escape the prusik)

Are you typically hanging with all your weight in the harness, or are you leaning off the wall?

Interestingly - all your weight is on the harness, but the wall is still what makes the difference. Suspension trauma is basically a bloodflow issue, so resting against a wall lets you keep your feet elevated and your quads active, stopping blood from pooling. The catastrophic case for suspension trauma is hanging limp and unconscious, since it lowers your feet while stopping muscle use or even fidgeting to boost circulation.

The vast majority of your weight is in the harness, but there is some portion of the force vector that's going into the wall as well.

But you're right, the weight distribution isn't really what matters in this case.

If the belay stance is a ledgeless hanging belay and the climber above you is slow, you can be hang as much as you end up wanting. I'll end up putting a hip into the wall to give my feet a rest.

But even during super long belays, it's unlikely for the belayer to be motionless for even ten minutes.

I would assume the average rock climber is lighter and more athletic than the average tower worker, and they’re probably not also carrying heavy tools and hardware.

We're carrying more tools and hardware - unless we're top-roping, and in that case none of these issues exist.

Whenever i'm climbing outside i have a few lengths of dyneema or cordelette that i can rig into a prussick or kleinheist for self-rescue or for staying comfy at multipitch belays that don't have nice ledges.

I don't hangdog all that much, so i was actually unaware of this risk, but it's worth keeping in mind!

Dyneema is not the best choice for friction hitches due to its low melting point. This is primarily a concern when using it as a backup for abseiling or lowering, or in any situation where you may take a fall onto the friction hitch.

I know. I don't use it for raps, but it's just fine as a static or static-ish anchor.

This is less of a risk in a climbing harness due to the location of the tie in point. With the point in front of you at your waist, it is possible to shift your legs around even when free hanging. Think about doing a rappel on a long free hang. For me, I keep my legs in front of me and more or less above my waist. If you were tied in at a point on your back, as construction harnesses use, your center of mass is below the suspension point and the only position you can grab the rope is with your arms above and behind your head. Try doing a pull up in that positions, it is extremely hard.

I once was indoors as a "training dummy" who got stuck on-rope rapelling and waited for someone to come up from the bottom to pick me off. My "tie in" point was a rack at my waist on the front. It takes a while to do this as it's not easy to climb past someone in single rope technique. I definitely felt my legs starting to go numb, even when I was kicking them around to keep blood flowing. I was hanging in space. That experience hit home to show the reality of harness hang syndrome.

Last time I went skydiving I experienced something like this. I was doing a pair jump and you do it in a harness that’s attached to the skydiver with the parachute. When the chute opens you slide down/into the harness and it compresses around your thighs. The first time I jumped, the instructor told me to step on his feet so he could put some slack in the harness, but this time the instructor didn’t do that, so for the whole time between opening the chute and landing I was stuck motionless in the tight harness. I almost passed out, it was pretty scary.

About a year ago, I was flying a hang glider and accidentally had a parachute deployment, and I ended up suspended in a tree, waiting for a grounds crew to come cut me down. The first thing that my friend said when I called him was "stand up if you can". Suspension trauma is a real risk for pilots who get stuck in trees, and it's a subject covered during parachute education clinics for that reason.

Coincidence or what? I attended a Safety Course (Construction) this very day and was introduced to the term orthostatic trauma which is also called suspension trauma. It so happens that I also do tree climbing with ropes and am familiar with prusik knots for ascension. Everyone should experience the sensation of climbing a single rope - it is magic. And finally I suffered bilateral pulmonory embolisms that I am putting down to excessive sitting while developing. My consultant told me that "20% don't make it to hospital"! Chilling memories. This article struck me thrice.

Interesting to see this pop up here! I'm in the process right now of getting my team Tower Safety Certified by Comtrain and this is one of the things they learn about. They also have to practice both being rescued from a tower (while hanging limp as though they were unconscious) and rescuing someone else from a tower. Gotta stay safe out there!

Given the address in your profile I'd suggest you might also want to have your team have access to non-cell communications. Sometimes you're at a tower that doesn't have great cell reception and even if the team is able to rescue an injured member they won't be able to safely transport them and be stuck sending someone to find cell coverage and call for an ambulance.

That's very true! Fortunately in our case (at least with the company I work for currently) we don't do any work outside of cell coverage or more than a few miles from a hospital. Part of the tower safety process though is to decide before climbing the tower where you will take someone if they get injured and how you'll get them them, or who/how you'll call if they can't be transported.

Is this somehow related to feeling uneasy from skydiving once parachute is deployed as well? I sometimes feel like I am going to pass out. I had a scary situation while practicing multiple tailspins and free-falls on a sailplane and almost blacked out after the last one (basically couldn't feel anything and landed just by vision and mechanical yoke movements I couldn't feel at all.

> as you inhale, the mediastinal intrapleural pressure becomes more negative, leading to expansion of the lungs, and pressure drops in the RA, RV, SVC, and IVC. Right Atrial expansion increases the pressure gradient for venous return

So you're saying my lung volume has implications for the chance of deep vein thrombosis or possibly even for varicose veins? Great engineering right there.

A climber can reach the rope, put in a prussik and stand on it. No can do with construction harnesses. The rope's out of reach.

There are products available which enable one to self-rescue from a lanyard at your dorsal.

I started looking into a suspension system for Virtual Reality to increase immersion. I thought it was surprising that no one had made a harness type device. Then I came across suspension trauma and realized how complex an issue it would be to make something like that and take it public.

This happens also to hunters that fall from hunting in tree stands and are wearing a safety harness.

This is the stuff I think about when I find myself in an overly tight airline seat.

I am constantly and intentionally contracting my leg muscles when in an airplane. Mainly due to comfort issues, but I figure it is probably also helping blood flow.

Yeah, interesting timing. It also seems quite similar to the effect of high (downward) G-forces.

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