What forces can a body sustain?

In the last blog post on the [slaice] rope terminations I wrote that the forces being discussed were well above anything a human body could sustain without suffering injury. This statement of course begs clarification…

Quite a bit of research has gone into this matter, dating back to studies investigating injuries paratroopers were suffering back in WW2 when their parachutes deployed, seeking to better understand the mechanisms involved and prevent people from getting hurt. Also there is the research looking at injuries suffered by drives and passengers in car accidents, this is about impacts rather than falls, but of course there are parallels when it comes to the mechanisms involved.

In case of a fall, it is not necessarily the landing that will hurt you, but rather the deceleration.

Impact with a hard, immovable object (e.g. the ground and/ or structure) is one instance of deceleration, but falling into your climbing systems can equally lead to injuries caused by rapid deceleration.  Considering that we are all ultimately naught more than sacks of skin filled with bones and squishy bits and bobs, we do not suffer deceleration well – as the momentum of the squishy stuff wants to carry on moving it at the same speed. Sudden deceleration can therefore lead to significant internal injuries, such as haemorrhaging.

When using work positioning systems, European legislation requires that the Maximum Arrest Force (MAF) shall be limited below 6 kN (≈600 kg), for the US and Canada it is 8 kN (≈800 kg). During any activity liable to generate a MAF higher than that, the person shall be protected from a fall by use of a fall arrest system.

So far, so good. But of course this is not the whole story.

What is critical is how the force is exerted upon the body. A number of organisations and researchers have done work investigating this matter.

NCAP, of the crash test dummy fame, an organisation whose aim is to improve safety in cars, for instance, have shown significant spinal deformation as from side impact forces of 350 kg on upwards.

Also, the Mägdefrau report (“Human Bodies in Falls”) and Andrew Sulowski (“How Good is the 8kN Maximum Arrest Force Limit in Industrial Fall Arrest Systems?”) looked into the matter of how the direction of fall has an influence upon the severity of injuries sustained. When comparing X-, Y-, and Z-axis falls, both studies conclude that there are significant differences.

A +Z-axis fall could happen when a person is secured to a back up device on a ladder attached to a sternal attachment point on the harness. In this fall orientation, the resulting force compresses the spine. From a constructive point of view, the spine is well able to do so, with plenty of muscles and vertebrae to dampen the force.

A +Y-axis fall could happen as a result of attaching a lanyard to the same side D-rings of a harness (not recommended practice). The spine is less well equipped to deal with this kind of force – a shearing force across the spine. Yet there are large muscle groups to either side of the spine in the abdominal region which will help to dampen the force.

A +X-axis fall will occur when ventrally attached to a work positioning systems, e.g. when using a sit or work positioning harness. Our body struggles to handle this kind of fall, as there significant leverage exerted over the lower back in a whiplash motion in a direction lacking in structural stability (muscular or skeletal).

These mechanisms are reflected by the findings of both Mägdefrau and Sulowski.

As you can see in the chart above, whilst all six falls generated similar peak forces, falls one to four would have fractured a real person’s spine (a humanoid dummy was used for the tests, of course), falls five and six caused no visible damage. The difference between the falls? Falls one to four used a sit harness (resulting in a +X-axis fall), five and six a full body harness (resulting in a +Z-axis fall).

It is worth noting that the forces recored above are well below the 6 or 8 kN limit defined by legislation.

Sulowski’s findings are similar to those described in the Magdefrau report, where only in the instance of a +X-axis fall did the fall protection effectively limit the MAF to below 6 kN.

So what is the conclusion? Use fall arrest systems, attached sternally to our work positioning systems to ensure a +X-axis fall?

The answer to that is obviously no.

As we are working in work positioning systems these should by definition not generate a MAF, as the aim is to prevent a fall from occurring in the first place. I do however think these are interesting figures to have in the back of ones mind, as they allow you to put other values in perspective, for instance when discussing MBS for personal protective equipment which are double, tripple or even quadruple the forces discussed above. Incorporating robust safety margins and allowing for wear and tear is all very well, but we must remember that the human body is fragile and likely to be the weak link in the chain.

Well, that, and the anchor points we select in trees – but that is a whole different story.

Full body load on slaice? YES!

Recently there has been some on-line discussion regarding Teufelberger’s [slaice] rope termination and whether it is suited to support a full body load, e.g. when base-anchoring a stationary rope to a base anchor.

In order to pass, EN1891, the European standard for low stretch kernmantle rope (AKA semi-static lines) requires a MBS (minimum breaking strength) of 15kN for three minutes in a static pull for type A lines.

EN1891 is a stationary rope standard, so the 15kN termination strength requirement for Type A has proven suitable and sufficient since at least 1998. [slaice] fulfils all requirements demanded by this standard.

But what about the 5’000 tensile strength requirement which the Z133 ANSI standard demands of all climbing equipment, you ask?

Apart from there being a degree of ambiguity regarding this requirement – it seems it is more of a perceived than a clearly stated one – , it certainly does not apply to terminations. In fact, there is no defined termination strength requirement for climbing lines in Z133. Further, I would suggest that we need to consider configured strength vs. component strength. Let’s assume you take a climbing line with a MBS of 25kN (≈5’000 lbs) and tie a figure of eight knot to attach it to your base anchor. The exact amount the tight bend radii in a knot reduce the breaking strength by is a matter of some contention, yet depending on where you look, you will find reference to a reduction from anywhere around 60 all the way up to 80% (and if we are talking high-tech fibre, this figure will be even higher!). Taking this into account, your configured, knotted line ends up well below 15kN right away!

Interestingly, all the Z133 standard has to say on the matter of terminations is that ’Splicing shall be done in accordance with manufacturer’s specifications’ (this would be a pass for [slaice] in that case), making no further requirements regarding knotted or configured strength of cordage.

Add to that the fact that the European standards for harnesses require an MBS of 15kN and the whole concept of requiring a 25kN MBS for terminations becomes a bit nonsensical. And the US? Similar picture to Europe: as from 1 January 2018, the fall protection attachment elements of arborist saddles in the US will also be required to withstand a load of 15kN for 3 mins (ASTM F887-2016).

To put all of these numbers in perspective, it is worth bearing in mind that your body cannot survive these kinds of loads, so I would suggest that you can be perfectly at ease using the [slaice] to attach to your base anchor.

But there was that safety warning a while back, you say?

Yes, Teufelberger issued a warning due to a couple of [slaice] turning up with inconsistent diameters behind the stitching. Mind you, despite that, the termination still passed the 15kN test – just not for the required three minutes. So this was less of a safety critical issue and more of a cosmetic matter. I believe Teufelberger were right to admitting to the fault and communicating in a pro-active, transparent fashion.

One strong point of the [slaice] construction is that it offers a tiered resistance to wear and tear: part of its strength stems from a Dyneema tape which passes through the eye of the termination and is included in the stitching.  So any abrasion or damage which occurs to the mantle of the line will have no adverse effect on the Dyneema, which is almost like a second line of defence. This makes for a highly robust, resilient rope termination. This technique is applied to all Teufelberger/ NER lines with a thin cover, e.g. Fly and Tachyon. The classic 16-strand construction lines, Arbor Elite and Braided Safety Blue, have a sufficient volume of material and hence strength in the cover for this not to be necessary.

I love climbing on lines with [slaice] terminations. They are low bulk, easy to pass through pulleys, thimbles and rings and do not get caught in tight forks. I also like the fact that the length which is stiffened due to the termination is very short, which lends itself to techniques like climbing in a loop. I find when I go back to a line with a standard splice on it, this seems very clunky and bulky in comparison.

But hey, à chaqun son plaisir, this is simply a further tool to add to the toolbox. If it suits your style and you like it, use it – if not, don’t.

So let’s be clear: [slaice] is absolutely safe to be used as a termination on arborist climbing lines in a PPE context for both stationary and doubled configurations.

No flow, no fun

There are a number of factors which will have a direct influence on levels of risk a person is exposed to…

How competent is the operator who is exposing themselves to the risk? How long is the exposure time? How serious are the potential consequences? Is the operator aware of the risks involved with the activity? What mitigating actions are in place to reduce the risk?

The first day of vertical-connect was dedicated to discussing various facets of risk. To me the emerging mosaic of aspects was truly fascinating, as it showed clearly to me how complex this topic is. Yes, it is true that we are often not very good at recognising risk and objectively assessing the actual risk we are exposing ourselves to and are prone to falling prey to biases which can cloud our vision in regards to real risks, yet at the same time it is possible to diligently manage risks in a efficient fashion, allowing people to survive in extreme environments

Jeanette Büchel from SUVA, the Swiss health and safety organisation explained how perception of risk can differ significantly from person to person and also how there can be a mismatch between the probability we identify of an incident occurring and the likelihood of it actually affecting us.

The chart above illustrates research conducted by Lennart Sjöberg and shows how we are able to identify risks, in the graph above with spikes when it comes to death due to alcohol and smoking, yet at the same time cannot correlate this likelihood with a probability of it also affecting our family – or even less so us personally. This is a classic case of It won’t happen to me. In turn this can have an adverse influence on our overall risk perception and ability to assess potential negative outcomes.

One person whom one cannot be accused of not considering risk down to the n-th degree is Hans Meier, another speaker at vertical-connect.

Hans is a cave diver and specialises in very, very deep dives. I was blown away by the degree of risk management that this intensely inimical and hostile environment requires. The water is a couple of degrees above freezing, space is often very confined, accesses are very difficult and long and decompression time can be up to eight hours for deep dives.

In the dark.



When diving in caves, Meier use a rebreather, which stores the exhaled gas in canisters (see images above), also he is constantly manually adjusting the mix of gas he is breathing. Due to the cold he heats the air he is breathing, wears a wet suit with heating coils and any number of layers – as well as a Therm-a-Rest mat wrapped around his torso, further he monitors his core temperature to avoid becoming hypothermic. On top of that he needs to constantly monitor his environment, his breathing and mental state as well as having a very clear idea of his orientation in space, which can be a challenge due to darkness and lack of reference points.

The truth is though, despite this very elaborate and dilligent process of risk management the environments that Hans is diving into, the smallest error of judgement or unforeseen incident would have immediate, serious or even fatal consequences.

Needless to say, by the end of Hans’ talk I felt more than just a bit claustrophobic and out of breath!

What did I take away from this?

Umm… what we perceive as being intensely risky is not necessarily what is going to harm or kill us, viewed from a statistical point of view.

Yes, of course, what Hans Meier does involve a very high risk, yet he is aware of this, is highly competent and goes to extraordinary lengths to mitigate these risks. Yet viewed from a greater distance, the guy sitting on his couch stuffing his face with crisps and downing one beer after another whilst watching a program on TV program about base jumpers (These guy are nuts! I won’t feel sorry for them if one of these silly sods kills themselves, they are asking for it!), is probably unknowingly exposing himself to greater risk of dying of a coronary condition associated with a sedentary life stile as well as a unhealthy diet and consumption of alcoholic beverages than the very base jumpers in the program his is watching. Statistically, more people die of heart attacks than B.A.S.E. jumping.

So I suppose what I took away from a day discussing risk is the need to be aware of what I am doing, of being attentive, methodical and diligent in monitoring my surroundings for unforeseen or changing parameters – no earth shattering insights, admittedly. One point I was struck by though was the opening question which Tom put to the participants of a panel discussing whether there is a different risk acceptance in professional and recreational contexts, when he asked them what they think of the motto No risk, no fun.

Personally, I believe that the aim cannot be to eliminate all risks from our lives. Apart from this not being possible, risk is an important evolutionary motor forcing us to become better at what we do, work out solutions and apply our creativity. So in my perception when I am confronted with a challenging climb, it is not the frisson of risk I am chasing, it is that sense of flow which lends the situation a sense of almost crystalline clarity, where one action flows into the next, where all else becomes a bit less significant and I am totally immersed in the moment.

So I would argue that it should actually be No flow, no fun.


Planning ahead

Living in the future? It certainly feels like it sometimes. These past few days I seem to have been planning ahead rather a lot. On the one hand we met in Hamburg last weekend to discuss next year’s Climbers Forum in Augsburg, which is shaping up nicely.

On the other hand I was very glad to finalise the graphics for the poster for next year’s vertical-connect. Thanks to Knut Foppe for the original photo which inspired the image.

Also, we decided upon the two day topics: Resilience and Access.

The event is now planned for Thursday and Friday, leaving the weekend free people to offer supplemental workshops and events in the area, such as mountain or canyoning tours, tree climbing or rescue workshops etc. …

I am looking forwards to working towards this event, certainly a date to put in your diary. Again, we will offering simultaneous translation between French, German and English.

In due course, further info will be published via our website, www.vertical-connect.ch, as well as via the vc Facebook page.

Novel pruning technique

Everybody seems to be talking about drones at the moment. Either getting excited about them – or hot under the collar. Tree care is not escaping this trend, for example to visually inspect trees from aloft or to install a throw line, as Nick Arraya demonstrated the other day in a video, to name but two examples…

This pilot in Connecticut however took it all to another level when demonstrating this novel way to prune a tree. Not so sure about some of the angles on those cuts though.

Ah, I’ve got it! Maybe he or she was pruning for habitat? 😂 Extreme retrenching, anyone?

Rather elaborate and costly mind you, if you intend to invoice the client for a Cessna for every tree you prune!

Yin. And Yang

I was watching one of Richard Delaney‘s videos the other day, where he discusses coiling a rope…

A, I thought he makes a number of interesting and valid points, such as layering the coils, allowing you to reverse the process cleanly or also leaving the ends longer so that they cannot get trapped in a coil causing a tangle – and B, this demonstrated how, given some thought, you can discuss matters that some might discard out of hand as blindingly obvious. Which obviously they are not, QED. Small things do indeed matter.

The other thing it reminded me of was the splicing workshop with Stanley Longstaff in the fire brigade station up in Glottertal in the Black Forest back in 2000. Or was it 2001? Be that as it may… we were wrapping up a major splicing session, moving the gear downstairs, when Dirk managed to stumble and fall down the steps with a box containing a kilometre of rope, spilling it all the way down the steps.

If Richard’s take on coiling a line is yang, the resulting mess of the lobbing a thousand meters of rope down stairs was most certainly yin. Talk about a major mess… nothing controlled about that unravelling!

Stanley of course passed away ten years ago this year and is sorely missed. He leaves a big hole in our community and deserves to be remembered for the passion, humour and music he brought us over the years – not to mention his deep understanding and love for all things rope.

Not forgetting you, big man.

vertical-connect 2017: Friday evening, Saturday and summary

Friday evening

The Friday evening is an integral part of the event, allowing people time and space to meet, chat, network and generally let their hair down. The evening kicked off with a dinner, accompanied by Dani Vonwiller’s photos of the day being projected, followed by general socialising, over by a fire bowl and a bar the lads from Vertic put up for the event.


Saturday’s topic was Connections and Connectors. The first speaker was Renè Comin from Italy talking about the work they are doing on the Bosco Verticale in Milano, a pair of residential towers designed by Stefano Boeri with a shrubs and trees integrated into their facade. This work requires arborist as well as industrial rope access skills. It was fascinating hearing Renè describing the planning process, the challenges they faced and the solutions they found.

This was followed by Ursula Briner talking about self-coaching in stress situations, about maintaining connections to what is going on around you. She was able to communicate this rather abstract topic in very clear and concrete terms involving the audience.

Next up were three talks on karabiners and connectors, with Martin Zgraggen discussing properties of aluminium, Albert Wenk sketching the evolutions of karabiner design and Puk sharing his thoughts on karabiner maintenance and lubrication as well as fail criteria.

Meanwhile Knut Foppe had set up a major gear fest under the circus tent outside, where he discussed a differentiated approach to connectors, comprehensively explaining the qualities, strengths and weaknesses in the various options of connectors we have when establishing connections.

The final talk was by the Fauchère brothers of Air Glaciers, a helicopter outfit with a number of bases all over Switzerland which performs a lot of transport and rescue operations. They discussed requirements and design considerations they make of connections when flying equipment of persons on longlines or winch lines. Fascinating stuff…


OK, I will admit to having been rather upset, after weeks of uninterrupted sunshine and heat, for the weather to turn right on the day of the event, for driving rain for most of Friday and Saturday, for the sun then to come out on Sunday morning, which almost added insult to injury.

Having said that, we had a good turnout, we managed to weatherproof the event as much as possible and people just generally mucked in. This is the flip side of doing this event in the mountains. Mountains do not do things in half measures: the weather is either stunningly beautiful – or abysmally horrible. I was glad of the sunshine on Sunday morning, as it showed once again, that this really is the ideal location for this event, with all the possibilities which the training centre of the cable car association offers – amongst others.

One thing which stood out for me was working with Sasha Köhler, who moderated the event. Sasha was witty, engaging and professional in the way in which he led the audience through the days. Interestingly though, he never put himself in the foreground, but rather used his position to create a stage for the speakers.

I am confident that vertical-connect can continue to grow. The whole dynamic and breadth of topics covered is unique and I look forwards to evolving it further. A number of changes have already been discussed for next year which will make attending even more attractive – more about this in due course.

The dates for next year are Thursday and Friday, 30 and 31 August 2018, more info in due course under vertical-connect.ch. Next year again with English and French simultaneous translation. Consider yourself warmly invited.

Photos courtesy of Dani Vonwiller and Tom Nickel.


vertical-connect 2017: Set-up and Friday

I am always amazed by how fast events you work towards come and go. The same holds true for this year’s third edition of vertical-connect, an interdisciplinary event we run in Meiringen in the Bernese Alps (yes, the same place where Sherlock Holmes fell down the waterfall with Professor Moriarty… it would seem they were not tied in).

What distinguished this year’s event?

A lot of water. We were battling serious amounts of rain from Thursday afternoon, during set-up, through the event – until the sun came out again during tear-down. Huh. We managed to get the event fairly weather proof, rigging a large tarp over the spectator space and putting up a large tent for the vendors. Still a bit of a pity, but there you go.

The weather-proofing  required some interesting rigging… it is amazing what you can do with a large tarp and 200 meters of Dyneema, plus a miscellaneous bunch of odd bits of lines and devices to tension them with.

The audience

We had a great turn-out of people from a wide range of on-rope disciplines from Friday morning onwards. As we were offering French and English simultaneous translation, the crowd was also very diverse in regards to where people came from. One of the things that stood out for me was how the line between people attending the event and generally mucking in was blurred. A big shout goes out to Peter and Jan from the treemagicbeers-fame. They were there from start to finish and did a stunning amount of work.

I was blown away by the over-all quality of the talks. The day-topic of Friday was Risk, Saturday was Connections and Connectors. It was one of those occasions when you gain real insight during an event. Part of the reason for this was the different angles and perspectives of the same topic.


For risk, for instance, where was Jeannette Büchel, a psychologist who works for the Swiss Health and Safety discussing how people perceive risk and why we respond to it differently. Jeannette’s talk gave a very comprehensive and lucid introduction to the topic.

This was followed by Hans Meier, an extreme cave diver… what can I say? I was gasping for air by the time he had finished. Talk about managing risk down to the n-th degree, yet the environments he is exposing himself to are so intensely hostile that the smallest miscalculation would likely have fatal consequences (I will write more about this at a later point in time).

After lunch break there was a podium discussing the whether risk is perceived the same way in a professional or recreational context. The panel was made up of Stefan Siegrist, one of the top Swiss alpinists, Patrick Zürcher, an arborist, trainer and work safety expert, Pit Bangeter, the president of the adventure park association and Christian Bollinger, also a work safety expert who works for a large insurance company. Tom Hofmann who was the moderator kicked off the discussion round by asking how the participants felt about the statement No risk, no fun. I thought that the statements by the people sitting up front, as well as opinions offered by people in the audience were fascinating. This could certainly have been discussed further or in greater depth, but suffice to say that whilst we may all agree that we can manage risk, I am not sure we are all talking about the same thing. Again, I will write more about this in due course.

After that, due to the weather going atrocious on us, I did my That’ll be alright talk, featuring Chabris’ and Simon’s invisible gorilla. I always enjoy doing that talk, also, for me it is a constant process of stripping it further down to the essential point you are trying to make, i.e. this time I removed all of the numbers and statistics out of the presentation – ultimately all this does is introduce unnecessary noise and distract from the message.

Next up were the two outdoor presentations…

First off we did a theatre illustrating three scenarios which ended in a system failure – in the pouring rain. But it was a blast! I won’t give away too much, as I would like to do this again at some stage, but my impression is that theatre is a very suitable medium to illustrate mechanisms that everyone is familiar with – without falling into the trap of moralising. Somehow it is easier for people to identify with what is being portrayed without feeling they have been rumbled. The challenge from planning the scenarios is not to simply turn it into a slapstick-number. Of course there are funny aspects, but what you are trying to communicate is anything but. After each scenario we analysed with help of a spiderweb diagram what the main factors were which caused the system failure.

The final scenario, where the climber and the groundie are embroiled in some serious conflict, ends in the climber accidentally dropping a sizeable log on the groundie. We replaced Florim, who was acting the groundie with a mannequin – for obvious reasons. The log knocked it’s head clean off, which then went bouncing away 🤢… grooooooss, I felt vaguely traumatised.

Which leaves us with this pic by Tom Nickel, which made me laugh as it feels a bit like a Stihl calendar photo shoot gone seriously wrong!

The second practical demo looked at the question whether there are situations where best practice requires double tie-in, yet where it may be better to use only one. Three short demos for this by the mountain guides, arborists and the Geneva high-angle rescue group.

vertical-connect challenge #1

The challenge took place on Friday evening and was the result of discussions regarding how to encourage a bit more participation by the audience. Michel Bischoff and Freddo Hunzicker came up with the goods, creating a course allowing two teams of three to demonstrate proficiency in a number of on-rope skills.

  • Throwline across shark-infested waters,
  • ascending onto the tower,
  • hauling a 100 kg log up the tower,
  • lowering it down the slide-line, and
  • finally using a grappling hook to place a line back across the shark-infested waters to then travers them in three tiny nutshells.

All this took place in the driving rain, a very impressive show by both teams…

Thanks to Dani Vonwiller and Tom Nickel for the photos.

vertical-connect… what a blast!

Back down from the mountains, gear dried, sorted and stored – and so vertical-connect 2017 becomes history.

What can I say?

If you weren’t there, you missed something (apart from the weather, that is). As I am feeling a bit weary right not, you will have to bear with me and be a bit patient for more pics and thoughts. These will follow in due course – but for right now, here is a first taste, a rather lovely video which Vito filmed and edited.

Thank you very much, Vito.