BLUE LIGHT SPECIAL - Hammer use to hammer nails, with "bionic" prosthetic hand, poses tricky Catch-22 for Cybathlon 2020 [review]

The Cybathlon 2020 race rules confront us with two interesting Catch-22 aspects:

-hammering (if not other dangerous) activity that is not endorsed by "bionic" hand manufacturers

-use of damaged / perforated covers, not endorsed by Ossur [link]

A hammer, particularly a cheap or small one, even more so than a heavy dangerous "real" hammer, is an unlikely tool to use with an ~80 000 USD myoelectric "bionic" device that is specifically built to sustain only the lightest of work. And the subject of hammering, technically, as arm amputee with a prosthetic arm, has become relevant since the Cybathlon 2020 directors [link] have taken it upon themselves to make it a "discipline".


(C) MC Hammer

Before that, we hammered thoughtlessly and safely - but now 1? Now, if ever, the Cybathlon 2020 was intended to stage or simulate (but not actually perform, oh no, sweat, yikes) a true real men [see use of term "real men": link] competition, you know, with real work [link], like, some six hours of sweat bathed carrying, bike up Stelvio pass, and loading work, and the likes, then it would be obvious that we finally would get to see real prosthetic arms at work ("work", you know). Like, hooks or jaws [link], man. But: the Cybathlon 2020 is an explicitly declared "bionic" arm competition, the ultimate cosplay show-off [link], which is a clear contradiction to any real work performed by real men. Which is where it becomes interesting to ask, how is this possible?

And in a nutshell: it is not.

The Cybathlon 2020 is now a circus like disability freak show [which it was beforehand] that not only lacks scientific relevance for useful prosthetic arm development in the direction of real work. It now appears to have degraded to the level of some shady street car races, as the following circumstances and aspects appear to imply.

The Catch-22 of hammering with a commercial "bionic" prosthesis such as the iLimb is twisted and will be outlined as follows, and with that, it is certainly one of the most twisted Catch-22s we have seen in a while:

1 - Insurance is required for Cybathlon 2020 participation: from Discipline Registration Form for Teams Cybathlon 2020: "The registrant will be asked to submit further documents and forms to assure safety of the device and insurance of the technology provider and pilot". "Adequate proof of insurance for all team officials, namely against accidents, injuries, and personal liability. In any case, insurance is the team officials’ own responsibility. The team officials will be asked, onsite, to sign a registration sheet, including insurance statements. If that document is signed, the CYBATHLON organisers must and will assume that adequate insurance coverage has been obtained as requested." 2. The fine print is funny as it is in the circus directors' interest to make sure their "tasks" can be legally insured and thus performed. All other is putting devices and people at risk.

2 - The act of hammering with a "bionic" prosthesis does not appear to be endorsed by manufacturers and certainly does not appear to be covered by warranty. Much rather, I also have correspondence with Ossur that indicates that they do not one bit identify their iLimb device to be suitable for hammering,  just as the device is not built for using a drill hammer and such3. The device's user manual [link] clearly states that the iLimb revolution hand is not be used in any activity that "may cause injury to a natural hand". In direct words, the manual states: "Do not use for (..) activities that may cause injury to a natural hand".The related warranty statement clearly excludes any activity that risks to injure a normal human hand4. So directly against their own product use specifications in context of CE laws, Ossur has their representatives hammer away at Cybathlon events5, while the hammer itself constitutes an ill choice as well.

3 - So, no insurance should cover damages of a "bionic" hand as caused during any act of hammering (or light bulb breakage)That the initiators of Cybathlon 2020 clearly expect also broken light bulbs6, as well as generally risky behaviour of the participants7, is evidenced in their own writings.

4 - Hammering - just as handling a light bulb - is an activity that may cause injury to a natural hand. The one particular prosthetic design and build that has the capacity to withstand full force hammering is - and I am not any longer happy to say that here, as "painfully" obvious is also that (i.e., painful) - the body powered arm, and then only when built with an extremely sturdy wrist and when equipped with a metal split-hook. That setup can be used, generally, for real work, including hammering. For anecedotal reference, I identified these approximated accelerations as typical with my body-powered arm (strapped mobile phone to socket at wrist level, obtaining absolute values of maximal accelerometer readouts):

  • normal wear and activity such as making coffee causes a maximal wrist connector level acceleration of up to ~18 m/s2
  • when I type carefully and slowly and casually, accelerations at wrist level are up to ~16 m/s2
  • when I use a light hammer, accelerations up to ~24 m/s2
  • when I use a heavier hammer and more impactful hammering, up to ~45 m/s2 acceleration
  • when I type vigorously and fast, and move forward with speed, accelerations are up to ~34 m/s2 - explains how commercially sold wrists fell apart under my use for typing, which is why the declaration for accepted or not accepted use should contain results of proper physical testing

This will have me estimate that in excess of around 20 m/s2, accelerations risk to cause serious cumulative damage to typical body powered commercial wrist connectors. Myoelectric wrist connectors are at least a class lower in terms of robustness; they allegedly die in situations such as trying to stick shift a car.

5 - The hammer type that is proposed for the Cybathlon 2020 in not even a good hammer for normal hammering! The circus directors of the Cybathlon 2020 require their hammer to have a wooden handle (painted BLUE), weighing 450 g, with a 21 x 29 mm cross section of handle size 8.

These hammer dimensions are not ideal for normal use, as it is a hard handle that imparts all vibration to the poor wrist and hand that has to hold it for hammering. Now, there is such a thing as the ideal hammer. Ideal weight: 900 - 1750 g. Ideal handle diameter: 65 mm.Ideal grip surface characteristics: foam rubber, suede or adhesive tape:

From Mital, A., & Kilbom, A. (1992). Design, selection and use of hand tools to alleviate trauma of the upper extremities: Part II—The scientific basis (knowledge base) for the guide. International Journal of Industrial Ergonomics, 10(1-2), 7-21 [8]: fatigue and discomfort have been related to handle angle and work orientation in hammering (Schoenmarklin and Marras, 1989), and to tool shape and work height in work with screwdrivers (Ulin et al., 1990; Ulin and Armstrong, 1991). Also, it is well established that poor design of the grip of a tool leads to exertion of higher grip forces (Cochran and Riley, 1986; Kilbom et al., 1991) and to extreme wrist deviations (e.g., work with pliers - Tichauer and Gage, 1977) and, therefore, to more fatigue. (...) Tool type. The majority of injuries (80%) are inflicted by non-powered hand tools due to the widespread use of non-powered hand tools. The four highest injury-causing non-powered hand tools are knife, hammer, wrench, and shovel. Among the powered hand tools, saws, drills, grinders, and hammers are involved in more injuries than any other hand tool. Type of accident/exposure. In the case of non-powered hand tools, 71.2% of all injuries are caused by 'striking by' or 'striking against' the tool. Overexertion is the second leading cause. 'Caught in' or 'betweens' and 'falls' contribute the least. The same types of accidents are responsible for most injuries in the case of powered hand tools. 'Struck by' and 'struck against' types of accidents are caused by saws, drills, hammers, and grinde (...) When large forces are exerted on the handle(s) of a straight tool, the wrist is deviated in the direction of the ulna. This causes reduced strength and endurance and leads to fatigue. In addition, the carpal tunnel is probably compressed and there is a risk of carpal tunnel syndrome. To avoid these situations, Armstrong (1983) recommends that large forces, when exerted by hand/arm on a workpiece through a hand tool, should be parallel to the long axis (length axis) of the forearm. The tool handle axis should be oriented at 80 ° from the long axis of the tool (pistol grip) whenever large forces are to be exerted on a workpiece (Fraser, 1980). For hammers, Konz (1986) concluded that a 10 ° bend is preferable to subjects. Both, Konz (1986) and Schoenmarklin and Marras (1989a), concluded that the angle of bend does not influence performance. Vertical hammering, however, was reported to be more difficult, less accurate, and more stressful and fatiguing  (Schoenmarklin and Marras, 1989b). (...) With many power grip tools (axes, hammers, saws), and with power tools (especially those with external power supply through pneumatic or electrical leads) weight is frequently a problem. In order to reduce fatigue, the tool should not weigh more than 2.3 kg (Greenberg and Chaffin, 1977; Eastman Kodak Company, 1983). However, if the center of gravity of a heavy tool is far from the wrist this weight limit should be further reduced. This is also corroborated by Johnson and Childress (1988), who observed that powered screwdrivers weighing about 1.12 kg or less do not produce significantly different magnitudes of EMG activity. The subjective assessment study of workers to determine the weight of the tool, conducted by Armstrong et al. (1989), also indicated that workers find tools weighing between 0.9 kg and 1.75 kg feel 'just right'. (..) For power grips, the recommended diameters are influenced by the hand size (Greenberg and Chaffin, 1977; Kilbom et al., 1991). According to a Swedish expert group (Jonsson et al., 1977), power grips around a cylindrical object should surround more than half the circumference of the cylinder, but the fingers and the thumb should not meet. Up to a certain grip diameter, grip strength increases with grip diameter, but beyond a certain point the grip strength starts decreasing as the grip diameter increases. The optimum grip diameter is 65 mm according to Hertzberg (1973), and 51 mm according to Ayoub and LoPresti (1971). (...) The grip surface should be slightly compressible, nonconductive, and smooth (Konz, 1990). Compressible materials dampen vibration and allow better distribution of pressure. The grip material, however, should not be too soft otherwise sharp objects, such as metal chips, will get embedded in the grip and make it difficult to use. The grip material should not absorb oil or other liquids and should not permit conduction of heat or electricity. (...) Foam rubber grip is preferred by users as it reduces the perception of hand fatigue and tenderness (Fellows and Freivalds, 1991). It, however, increases tool grip force. In general, metallic handles should be avoided or encased in a rubber or plastic sheath (Konz, 1990). Grip surface area should be maximized to ensure pressure distribution over as large an area as possible. Field and laboratory investigations suggest that excessive localized pressure sometimes causes pain that forces workers to interrupt their work. Pressure-pain thresholds of around 500 kpa for females and 700 kpa for males have been registered, the most sensitive areas being the thenar and the os pisiforme areas (Fransson and Kilbom, 1991). During maximal power grips these values are greatly exceeded. The frictional characteristics of the tool surface vary with the pressure exerted by the hand, with the smoothness and porosity of the surface and with contaminants (Buchholz et al., 1988; Bobjer, 1990). Sweat increases the coefficient of friction while oil and fat reduce it. When pinch force increases, the coefficient of friction is reduced. Adhesive tape and suede provide good friction when moisture is present, and would be good handle materials for reducing grip force requirements in workplaces with a lot of moisture (Buchholz et al., 1988). In addition to the surface material, the pattern of the surface influences the perceiued discomfort markedly, and is, therefore, a factor of significance in the acceptability of the tool. When the hand is clean or sweaty, the best (maximum) frictions were obtained with smooth or finely patterned surfaces (Bobjer, 1990). (..) The duration and repetitiveness of use of a hand tool profoundly increase the risk of occupational injury, either alone or in combination with factors discussed above (Hammer, 1934; Kurppa et al., 1979; Luopajarvi et al., 1979; Kuorinka and Koskinen, 1979; Cannon et al., 1981) [8].

So the "organizers" of Cybathlon 2020 love themselves a bit of hammering without reading nerdy hammer papers beforehand, but that aside, they are likely not that interested in the act itself.

6 - During the Cybathlon 2020, "spotters" that see "bionic" hand users about to "hammer" will dramatically intervene and save the day! The Cybathlon "organizers" seemn to shift the burden of responsibility of any remaining risk of injury to "spotters": they apparently have designated assistants (unpaid volunteers maybe?) on the scene of competition, that apparently are required to intervene at any impending act of hammering (or light bulb breakage). Those of the "spotters" that read the regulations and know the predicament of the "bionic" hand wearers will certainly have to intervene and stop any hammering or light bulb breakage at the latest some split seconds from occurring. Drama ensues! As intriguingly, they have to intervene at the moment of "risk" - not at the moment of already made damage. 9

With that, we have an elaborate six-step Catch-22. While it does not amount to excellent technical development or engineering, it certainly seems to enrich the already dense content that makes up for much of the sociological aspects that also seem to hover, like clouds, over the aspects of applied CE-norms in the context of prosthetic arms.


Insurance reactions

The Swiss Accident Insurance (SUVA) seems to be entirely unaware of the issues and posts this10 :

With that, the Swiss Accident Insurance (SUVA) seems to be unaware of the relevant issues - whose recognition is admittedly tricky and requires actual knowledge of "bionic" hand use problems - and posts this: "at the Cybathlon at Zurich main station athletes show how they "master" everday-situations with innovative assistance systems".

That is not actually true. They master "a very small selection" of problems, most of which are not everyday-situations. Grasping cubes or spheres is not at all an everyday situations. Hammering nails by holding a hammer with a "bionic" prosthesis are not everyday situations at all - no one hammers like that, hell, the manufacturer does not allow it! Also, swapping light bulbs is not routinely done with a "bionic" hand - far too dangerous, far too clumsy, far too inconvenient. So we can safely assume they were just taken away with the advertising.

So, SUVA representatives seem to have no qualms about the whole thing at all. Is that a sign that insurance representatives have issues with what they ought to know? Is this an instance of "in chaos, there lies chance"?

Critical comment

The subject of a particular task can be properly analyzed and discussed, even if one works as an academic.

And there, also the banal if not barbaric use of excessive blunt force such as "hammer against nail" can be subjected to proper analysis, and only if it is to alert everyone to the clear fact that use of a prosthetic device of myoelectric proportions for, say, hammering is pitch black off-label use and even though it is not forbidden by law, the damages can be overly expensive. More importantly, hammering usually is premeditated, planned and damages are cold bloodedly taken into account - such as here - so hammering usually does not come out of urgent necessity. Then, its risks can be weighed and a better plan (in theory) can be made. Hence, it is clearly not allowed or accepted by prosthetic arm manufacturers that build "bionic" hands such as evidenced by their writings both generally (see above) and specifically pertaining to hammering when asked directly (see, also, above).

Any "fool with a tool" (including, but maybe not restricted to, me) knows that holding the nail with the "bionic" prosthesis before trying to hit the nail hard is as dumb as a bag of hammers because hitting a pricey delicate prosthetic finger warrants pricey repair outside any warranty, but also and worse, hitting a nail by holding the hammer with the prosthesis risks to damage the delicate electric wrist connector and the one human own hand holding the nail as well, so using the hammer that way around is even dumber than a bag of hammers. My assessment is dead right, and if only I just refer to myself, if ever I had hammered in such a way this would be spot on.

In short (and that is the "dark logic" here), anyone that starts a sentence with "I will hammer a nail using a "bionic" hand and *" has lost all further polite explanations at the moment of "*". Instantaneously. Repairing a "bionic" hand finger is one thing (remove glove, remove screw, replace finger, replace screw, replace glove) but repairing a wrist connector can be a real bitch (socket works, etc.) not even speaking of hammering one's own biological finger. Anyone that understands prosthetic arms knows that, too. Which, on the other hand, means that those that figured, hey, "bionic" hands, "let's hammer", by inference, are entirely clueless when it comes to the domain of prosthetic arms. Which isn't exactly news.

So, who approved that task for the Cybathlon 2020? Other than clueless individuals, I would say anyone that works in selling and repairing prosthetic arms and that serves as advisory on the board of the Cybathlon games, and that went "cool, hammering with "bionic" hands", I guess, directly may benefit from repairs or new builds, financially. Regardless of insurance status, someone often benefits from specific damages. Because once you have approved of hammering with "bionic" hands, you reside at a very specific point in time, content and space: and you did not get to that point in time, content and space without a painful long trail of, ups, well, say, blood or oil or maybe both. And we did see that coming: if all you have is a hammer everthing else looks like a nail. Or, differently put: there are defined holes in the conceptual safety nets of society - the same holes actually, that cause the year 2020 to come, and that STILL has real working men like me rely on prosthetic body powered hooks as ONLY actually useful option. There is nothing sweeter than to be able to say, I told you so.

As we all know, there are people that resist common knowledge as well as both mechanical and biomechanical understanding of "what it is prosthetic arms should be, but are not, built for". That aside, the organizers of Cybathlon 2020 still seem to uphold the ideal that delicate technology may be best used to shred, wreck, bash and hammer, regardless of insurance options vice versa actual engineering aspects, without actually building a device that also hammers well using good hammers (none if which we will see at that Cybathlon 2020, unfortunately) - and all without paying for any damage themselves. While that seems neither particularly adult, nor particularly responsible, and while that sure as hell is not good engineering, it nevertheless sets a new tone for this "circus event", and there, it puts the bar higher than previously: it now puts participants in harm's way - and there are designated "spotters" that participate in dramatizing this in public. "Waaahhhh caught him before he could hit the HAMMER!!! 2 points"

The future looks bright for something like a hypothetical "Cybathlon 2024 / Extreme Cyborging - the Blood games", where we might have "bionic" hand knife throwers or  people with "bionic" hands that would use these to hold a chainsaw which will be used to carve a pattern into a leather belt that is worn by someone the organizers wish to possibly sacrifice. Insurances, warranty, spotters galore! There are no "questions" at this level that can be sensibly asked any more. We freeze with the type of mindset that unfolds itself in front or our eyes - and while it is all there already now, it seems like no one actually "sees" this. After all they "sort" amputees already under the subject heading of "materials" [link]. How Otto Bock or Ossur cooperate here, is impossible to understand. They really should do their own showcase.

Proper hammer

A hammer should generally be chosen that is fit for the task. Using small hammers may be a convenience owed to storage or transport, but using small hammers also is a risk. If one goes public, if one goes competition, if one goes industrial, if one goes real work, then proper tools should be a relevant aspect.

Proper prosthesis - and what is cool

The iLimb and the Michelangelo hand including their wrists are not built for hammering as the manual clearly advises to not use it since there is injury risk for a natural hand. A Cybathlon 2020 that has participants use what appears to be a rather undersized hammer with their iLimb or Michelangelo hand, given current manufacturer information, appears to violate the commercial use restrictions for that device, and, it implies that using undersized hammers in an academically organised competition to show good prosthesis use is in any way cool.

No, cool is different. Cool is when I, as end user and amputee, that ends up with entirely insufficient declarations and assertions as to what is or is not proper use, finds his own way out of that mess. That is cool. When I, as a user or prosthetic arms, identify that body powered prostheses can be tuned and tweaked with a extremely durable wrist (etc.), then I may well wear a prosthetic arm that totally sustains hammering. My prosthetic split-hook does not suffer great damages from getting hammered upon either, I can use that device to clearly perform activities that otherwise do injure a normal hand and there are no problems with that. But I work in a different league, a league that has far lower control error rates and far higher physical durability. And building my own parts, getting these insurance funded, and patenting my own stuff to allow all that, that is definitely very cool.

But if Ossur / Touch Bionics as well as Otto Bock etc. support an academic ETH competition using hammers with their own devices, while they are not immediately opposing such race rules or regulations, while telling users in their manuals and product descriptions that they are not allowed to do the same because obviously there is a risk of damage, and if the Cybathlon 2020 organizers set up an obscure Catch-22 as outlined above, to trick amputees into participating in their circus freak show, that is not cool.

How hammer use with an iLimb looks like (free preview)

Holding a light weight "hammerling" at the grip end is not good to get a lot of energy going. The whole setup is too wiggly.

Using the same lightweight "hammerling" by holding it around the middle of its grip results in better aim and thus minimally better energy transfer but, still, useless.

Using a real hammer is far better, while holding that one at the grip end still imparts impediment through instability. The hammer head swivels in a type of figure-8 loop because grip and wrist cannot be stabilised. After all, the manufacturer prohibits this use from warranty coverage as more importantly as an insight, this hand (and wrist) are simply not built for that. With a clear use outside any boundaries, I can afford that because among many things, I do have explicit official ethics approval for self tests with prosthetic arms in clear sight of side effects, secondly, my prosthesis is way past warranty coverage, and thirdly, I am an advanced builder and constructor with thousands of miles of tool use under my belt.

And so only a very heavy hammer gripped at the middle of the grip can be halfway accepted as sensible tool to get a nail in.

What you see here is, as stated above, neither insured nor insurable, nor is it covered by the warranty of any "bionic" hand manufacturer. Also the parts were not built for this use.

Disclaimer: Do NOT try any of this at home, at work, or at any Cybathlon event including 2020 unless you are sure this is explicitly allowed by manufacturer, and covered by both warranty and insurance.

Attention: And if any manufacturer such as Otto Bock or Ossur endorses or allows their "pilots" to (also) go hammer, particularly also in any attempt to also advertise for their products in that context [link], while banning that use from normal users, their CE-norm compliance (including the requirement that advertising must match device performance) should be very critically revised.

[1] H. Herr, G. P. Whiteley, and D. Childress, Cyborg Technology--Biomimetic Orthotic and Prosthetic Technology, SPIE Press, Bellingham, Washington, 2003.
  title={Cyborg Technology--Biomimetic Orthotic and Prosthetic Technology},
  author={Herr, Hugh and Whiteley, Graham Paul and Childress, Dudley},
  publisher={SPIE Press, Bellingham, Washington}
[2] [doi] P. Kyberd and A. Poulton, "Use of accelerometers in the control of practical prosthetic arms," IEEE Transactions on Neural Systems and Rehabilitation Engineering, vol. PP, iss. 99, pp. 1-1, 2017.
author={P. Kyberd and A. Poulton},
journal={IEEE Transactions on Neural Systems and Rehabilitation Engineering},
title={Use of accelerometers in the control of practical prosthetic arms},
keywords={Acceleration;Accelerometers;Elbow;Gravity;Motion segmentation;Prosthetics;Sensors;Accelerometers;Artificial Limbs;Prosthetic hand;Prosthetic limbs},
[3] C. M. Light, P. H. Chappell, and P. J. Kyberd, "Establishing a standardized clinical assessment tool of pathologic and prosthetic hand function: normative data, reliability, and validity," Archive of Physical Medicine and Rehabilitation, vol. 83, pp. 776-783, 2002.
  title={Establishing a standardized clinical assessment tool of pathologic and prosthetic hand function: normative data, reliability, and validity},
  author={Light, Colin M and Chappell, Paul H and Kyberd, Peter J},
  journal={{Archive of Physical Medicine and Rehabilitation}},
  publisher={American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation}
[4] A. Hussaini, P. Kyberd, and others, "Refined clothespin relocation test and assessment of motion," Prosthetics and Orthotics International, 2016.
  title={Refined clothespin relocation test and assessment of motion},
  author={Hussaini, Ali and Kyberd, Peter and others},
  journal={Prosthetics and Orthotics International},
[5] [doi] M. Sobuh, L. Kenney, A. Galpin, S. Thies, J. McLaughlin, J. Kulkarni, and P. Kyberd, "Visuomotor behaviours when using a myoelectric prosthesis," Journal of NeuroEngineering and Rehabilitation, vol. 11, iss. 1, p. 72, 2014.
AUTHOR = {Sobuh, Mohammad and Kenney, Laurence and Galpin, Adam and Thies, Sibylle and McLaughlin, Jane and Kulkarni, Jai and Kyberd, Peter},
TITLE = {Visuomotor behaviours when using a myoelectric prosthesis},
JOURNAL = {Journal of NeuroEngineering and Rehabilitation},
VOLUME = {11},
YEAR = {2014},
NUMBER = {1},
PAGES = {72},
URL = {},
DOI = {10.1186/1743-0003-11-72},
PubMedID = {24758375},
ISSN = {1743-0003},
ABSTRACT = {BACKGROUND:A recent study showed that the gaze patterns of amputee users of myoelectric prostheses differ markedly from those seen in anatomically intact subjects. Gaze behaviour is a promising outcome measures for prosthesis designers, as it appears to reflect the strategies adopted by amputees to compensate for the absence of proprioceptive feedback and uncertainty/delays in the control system, factors believed to be central to the difficulty in using prostheses. The primary aim of our study was to characterise visuomotor behaviours over learning to use a trans-radial myoelectric prosthesis. Secondly, as there are logistical advantages to using anatomically intact subjects in prosthesis evaluation studies, we investigated similarities in visuomotor behaviours between anatomically intact users of a trans-radial prosthesis simulator and experienced trans-radial myoelectric prosthesis users.METHODS:In part 1 of the study, we investigated visuomotor behaviours during performance of a functional task (reaching, grasping and manipulating a carton) in a group of seven anatomically intact subjects over learning to use a trans-radial myoelectric prosthesis simulator (Dataset 1). Secondly, we compared their patterns of visuomotor behaviour with those of four experienced trans-radial myoelectric prosthesis users (Dataset 2). We recorded task movement time, performance on the SHAP test of hand function and gaze behaviour.RESULTS:Dataset 1 showed that while reaching and grasping the object, anatomically intact subjects using the prosthesis simulator devoted around 90% of their visual attention to either the hand or the area of the object to be grasped. This pattern of behaviour did not change with training, and similar patterns were seen in Dataset 2. Anatomically intact subjects exhibited significant increases in task duration at their first attempts to use the prosthesis simulator. At the end of training, the values had decreased and were similar to those seen in Dataset 2.CONCLUSIONS:The study provides the first functional description of the gaze behaviours seen during use of a myoelectric prosthesis. Gaze behaviours were found to be relatively insensitive to practice. In addition, encouraging similarities were seen between the amputee group and the prosthesis simulator group.},
[6] R. M. Bongers, P. J. Kyberd, H. Bouwsema, L. P. Kenney, D. H. Plettenburg, and C. K. Van der Sluis, "Bernstein’s levels of construction of movements applied to upper limb prosthetics," JPO: Journal of Prosthetics and Orthotics, vol. 24, iss. 2, pp. 67-76, 2012.
  title={Bernstein’s levels of construction of movements applied to upper limb prosthetics},
  author={Bongers, Raoul M and Kyberd, Peter J and Bouwsema, Hanneke and Kenney, Laurence PJ and Plettenburg, Dick H and Van der Sluis, Corry K},
  journal={JPO: Journal of Prosthetics and Orthotics},
[7] P. J. Kyberd, A. Murgia, M. Gasson, T. Tjerks, C. Metcalf, P. H. Chappell, K. Warwick, S. E. M. Lawson, and T. Barnhill, "Case studies to demonstrate the range of applications of the Southampton Hand Assessment Procedure," The British Journal of Occupational Therapy, vol. 72, iss. 5, pp. 212-218, 2009.
@article {kyberd2009,
  author = "Kyberd, Peter J and Murgia, Alessio and Gasson, Mark and Tjerks, Tristan and Metcalf, Cheryl and Chappell, Paul H and Warwick, Kevin and Lawson, Sian E M and Barnhill, Tom",
  title = {{Case studies to demonstrate the range of applications of the Southampton Hand Assessment Procedure}},
  journal = {{The British Journal of Occupational Therapy}},
  volume = "72",
  number = "5",
  year = "2009",
  abstract = "The Southampton Hand Assessment Procedure (SHAP) was devised to assess quantitatively the functional range of injured and healthy adult hands. It was designed to be a practical tool for use in a busy clinical setting; thus, it was made simple to use and easy to interpret. This paper describes four examples of its use: before and after a surgical procedure, to observe the impact of an injury, use with prostheses, and during recovery following a fracture. The cases show that the SHAP is capable of monitoring progress and recovery, identifying functional abilities in prosthetic hands and comparing the capabilities of different groups of injuries.",
  pages = "212-218",
  url = "",
[8] A. Mital and A. Kilbom, "Design, selection and use of hand tools to alleviate trauma of the upper extremities: Part II—The scientific basis (knowledge base) for the guide," International Journal of Industrial Ergonomics, vol. 10, iss. 1-2, pp. 7-21, 1992.
  title={Design, selection and use of hand tools to alleviate trauma of the upper extremities: Part II—The scientific basis (knowledge base) for the guide},
  author={Mital, Anil and Kilbom, Asa},
  journal={International Journal of Industrial Ergonomics},

Keywords: IV, Invalidenversicherung, bionische Armprothese, bionic arm, bionic prosthesis, cross label use, unauthorized use, illicit use, warranty, repair, damages, SUVA, insurance, coverage, claim


  1. Task rules

  2. From the registration text:

    (c) Copyright Cybathlon

  3. Von Wolf Schweitzer an Ossur am 26 April 2019 - "Mich hatte interessiert, ob es Sinn Macht dass ich das iLimb im Bereich Werkstatt / Werkarbeiten einsetze. Dabei verwende ich Holz oder Metallteile, Bohrer, Hämmer, Akkuschrauber, Stichsäge, etc.; es scheint mir, als ob die Frage bezüglich der Hand selbst mit Ihrer Dokumentation wenigstens indirekt beantwortet ist wo Sie schreiben, dass "extreme" Aktivitäten bei denen eine normale Hand verletzt werden kann nicht durchgeführt werden sollen, nicht geeignet sind. Da bei Stichsäge, Hammer, aber durchaus bei relativ hohem Drehmoment beim Akkuschrauber/bohrer ein solches Verletzungsrisiko für jede normale Hand ganz sicher und jedenfalls vorhanden ist ("man muss immer aufpassen") würde ich daher schliessen dass Sie davon abraten / bzw. diese Aktivitäten nicht als sinnvoll erachten. Immerhin tut nach aufwendigem Hämmern, auch Schlagbohren, oder auch Akkuschrauberbohren oder -schrauben (demnächst mache ich wieder ein paar Dutzend Verstärkungsschrauben in unseren Holzzaun) das "normale" Handgelenk oft etwas weh, indem die Vielzahl der Belastungen doch eine gewisse Schädigung des Gewebes des normalen Handgelenks nach sich zieht. Sogar beim "nur" viele Texteingaben auf Tastatur machen lockert sich bei meiner Eigenkraftprothese über Wochen immer die Verschraubung es dort extrem stabilen Handgelenks im Eingussring, so dass daraus heraus klar wird, dass die Tastaturan"schläge" effektiv Schläge im mechanischen Sinne darstellen, die daher für die Anwendung zu berücksichtigen sind. So dass ich mich frage, ob das iLimb für derartiges gebaut ist, würde vermuten eher nicht aber ganz sicher weiss man es natürlich leider nicht. Während ich das für das iLimb (also die Hand) dieses vermutet hatte, dass es für Werkstatteinsatz mit viel Arbeit weniger gut ist, war ich bezüglich des HANDGELENKS also des elektrischen Konnektors Hand-Schaft völlig im Unklaren. Da ich auch einen Otto Bock Greifer habe, der jedenfalls starke Belastungen aushält, und der hervorragend an  das Handgelenk drauf passt, wäre der schwache Link das Handgelenk. Dazu finde ich in der Dokumentation nichts aussagekräftiges leider. Würde ich davon ausgehen, dass es ein starkes Rückschlagen wie beim Bohrhammer gut verträgt, dass Hämmern OK ist, oder andere starke Schläge, würde ich mal lustig loszimmern. Aber da ein Bekannter ein (vermutlich baugleiches / konstruktionsgleiches) Handgelenk anderen Fabrikates (entweder eine US-Firma, oder Otto Bock) nur beim Handschalten eines alten Autos ruiniert hatte, hätte ich vermutet dass diese Art konzentrische Steckverbindung, was es  im Grunde ist, dazu führen würde, dass Sie diese Aktivitäten auch fürs Handgelenk als "nicht OK" vermerken würden. Aber: ich weiss es nicht sicher. Daher meine Frage. Vielleicht könnten Sie daher Belastungsangaben zu den Passteilen der elektrischen Handgelenksverbindung suchen? Ich habe da dieses passive Konnektorteil, ohne Motor. Wo man die Hand draufsteckt und sie (manuell) verdrehen kann." --- Von Ossur an mich - 29 April 2019: "Die i-Limb Prothesenhand ist eine hochfunktionelle, multiartikulierte Vollhandprothese, die durch ihre vielseitigen, einfachen und schnellen Ansteuerungsmöglichkeiten sowie hochpräziser Griffmuster besticht. Wie Sie schon richtig erkannt haben, ist die Prothesenhand für handwerkliche Tätigkeiten, wie Sie sie beschreiben, nicht ausgelegt. Die Prothesenhand sollte nicht in Verbindung mit Maschinen mit beweglichen Teilen verwendet werden, die Sach- oder Personenschaden verursachen können, nicht für extreme Aktivitäten verwendet werden, die zu Verletzungen einer natürlichen Hand führen können, keinen Vibrationen ausgesetzt werden, keinen übermäßigen oder hohen Kräften aussetzt werden, insbesondere nicht an den Spitzen und an den Seiten der Finger und vor Staub, hohen Temperaturen und Stoßen geschützt werden. Diese Sicherheitshinweise beziehen sich sowohl auf die Prothesenhand als auch auf die zugehörigen Komponenten, zu denen auch der Koaxialstecker gehört, nach dem Sie explizit fragen."
  4. iLimb Revolution user manual: (..) Do not use with machinery with moving parts that may cause personal injury or damage (..) Users must comply with local regulations on the operation of automobiles, aircraft, sailing vessels of any kind and any other motorized vehicle or device (..) Do not use for extreme activities that may cause injury to a natural hand e.g. rock climbing
  5. The hammering is indeed approximated despite urges and clear product declaration warnings of Touchbionics/Ossur to not use the iLimb for exactly that activity, as video footage of the Cybathlon Karlsruhe Reha Care Trade Fair suggests. As the participation there is clearly endorsed if not paid for by Ossur, they enable a contradictory "advertising" of their own product use which is definitely questionable in context of the CE norms [link].

    Despite that, the Ossur representative wearing an iLimb undeniably hammers away, wearing official Ossur clothing of the same company that in no unclear words forbids us users to hammer away. And while you could say, cool they got us suckered - overadvertise, then hit us with the fine print: the CE marking legal texts do not allow companies to do that and pretend they sell a CE conforming medical device. People that pay for repairs etc know that, and that includes my insurance - they know that things are not what they seem with regard to CE labels. We all are not like a bit hm, unsure, or ambivalent, no. Sooner or later, we know.

    But they all seem to believe we don't. As it appears, not even a "spotter" seems to be stopping her.

    (C) Copyright video sequence Reha Care Fair Link

    So in short: this woman as representative of Ossur demonstrates the act of hammering - in a rather clumsy and not well trained way, but hammering it is. The Cybathlon demonstration is used as advertising or promotion by Ossur. In their mail to me, Ossur clearly said their device including the wrist was NOT meant to do that. Their warranty conditions and product use instructions do NOT allow hammering. CE-mark norms require that product advertising MATCHES what the product actually can do and does. So with a few strokes of a hammer, just a few seconds, and the problem is here and large. After that, it is interesting to see who recognizes that as such and more importantly, who does not recognise this. This rather elegantly tests the intellectual sharpness and knowledge base of all involved players within the narrow field of prosthetic arms. Do they really know what they are doing? And the results of that intellectual test of sorts are clear: we have a list of names of who all did not prevent this. They all have no clue about the realities of wearing a purchased device under product use instructions, warranty restrictions and insurance conditions given their delicate and fragile nature. - From the Cybathlon webpage (link) (link), we can see who is listed as actively involved in this: The CYBATHLON Strategic Board is composed of eight voting members. Members are: Robert Riener President [3], Roger Gassert, Vice-President [3] Joël Mesot (ETH President) Amina Chaudri (ETH Zürich Foundation) Christoph Joho (Meeting Director Weltklasse Zürich) Joe Manser (Local Councillor) Peter Wolf (Senior Scientist) - Ambassadors: The following people significantly support the CYBATHLON: Sarah Springman (Rector ETH Zurich) Frank Bodin (Advertiser) Kyu Jin Cho (Professor) Michel Fornasier (Give Children a Hand - [1] ) Heinz Frei (Parathlete) Thomas Heiniger (President Swiss Red Cross) Hugh Herr (Professor) [4] [1 René Huber (Mayor of Kloten) Jongbae Kim (Professor) Corine Mauch (Mayor of Zurich) Joachim Schoss (President MyHandicap) [3] Yoshiyuki Sankai (Professor) David Weir (Parathlete) - - Advisory Board The CYBATHLON Organising Committee is supported by an Advisory Board consisting of representatives from research, medicine, business and politics: Roland Auberger (Prosthesis Developer), Rüdiger Böhm (Motivational Coach), Thomas Böni (Prosthetist - he is head of a unit that also build prosthetic limbs) [3], Rainer Burgkart (Professor) [3], Lukas Christen (Former Parathlete and Coach), Gery Colombo (CEO), Rory Cooper (Professor), Armin Curt (Chief Doctor Paraplegia), Nicolas Gerig (Robotics Researcher), Moritz Grosse-Wentrup (Professor), Michael Harr (CEO), Ken Hunt (Professor), Masahiko Inami (Professor), Fabian Just (Robotics Researcher), Hanni Kloimstein (Head of Sport & Development), Peter Kyberd (Professor) [4][2, 3, 4, 5, 6, 7] , Christian Lohr (National Council and Member of the Commission of Social Security and Health), Patrick Mayer (entrepreneur and innovator), Brian McGowan (Equality Officer), José Millán (Professor) [3], Gernot Müller-Putz (Professor), Shuro Nakajima (Professor), Peter Neuhaus (Researcher), Domen Novak (Professor), Alex Oberholzer (Film Critic), Claudio Perret (Head of Sports Medicine), Mark Pollock (Explorer & Collaboration Catalyst), Abassia Rahmani (Paralympian), Raffaele Ranzani (Robotics Researcher), Georg Rauter (Professor), Markus Riesch (Project Manager Accessibility), Thomas Schauer (Professor), Kai Schmidt (Robotics Researcher), Diana Sigrist-Nix (Manager Therapy Management and Rehabilitation), Karin Suter-Erath (Paralympian), Kyoko Suzuki (Deputy Head S&T Office Japan), Simon Voit (Prosthetics Expert and Parathlete), Conor Walsh (Professor), Christian Wenger (Lawyer), Dominik Wyser (Robotics Researcher). Partners are: Maxon [2], EKZ, Schulthess Klinik, BNP Paribas, Ernst Göhner Stiftung, Swiss Paraplegic Foundation, Stadt Kloten, Cerebral Stiftung, MBF foundation, Pro Infirmis, Plusport [3], Hocoma.. Media partner is: Tages Anzeiger. Benefactors are: ZKB, Global Strategic Capital, Sandra Thoma, IASTED [3], 3M (Switzerland), Braingroup. Partnerships supported by: ETH Foundation. As patronage are listed: Daisy consortium, Zugang Fur Alle, MyHandicap [3], Procap, Swiss Handicap, Fragile Suisse, Mark Pollock Trust Org, Michel Fornasier Charity, Kanton Zürich Gesundheitsdirektion, Eidg. Büro für die Gleichstellung von Menschen mit Behinderungen, Inclusion Handicap, FMH, Schweizerische Multiple Sklerose Gesellschaft. They even claim, possibly outrageously, that "The above mentioned organisations and institutions support CYBATHLON with shared values and their expertise". - Labels: [1] This person has access to an iLimb and is a user [2] Appears to have experience building prosthetic arms or relevant components as a provider [3] Appears to be well networked to identify this as a problem [4] Appears to perform research in conjunction with prosthetic arms - The  other people or entities that were not highlighted appear to contain no relevant knowledge or exposure to prosthetic arms.

  6. From the race regulations (C) Copyright Cybathlon 2020: Bulb lights up after it is screwed into the bulb holder. If the blue lightbulb breaks into pieces, the task is failed.
  7. From the race regulations (C) Copyright Cybathlon 2020:

  8. (c) Copyright Cybathlon

  9. From the race regulations (C) Copyright Cybathlon 2020:

Cite this article:
Wolf Schweitzer: - BLUE LIGHT SPECIAL - Hammer use to hammer nails, with "bionic" prosthetic hand, poses tricky Catch-22 for Cybathlon 2020 [review]; published 20/04/2019, 10:28; URL:

BibTeX: @MISC{schweitzer_wolf_1643211655, author = {Wolf Schweitzer}, title = {{ - BLUE LIGHT SPECIAL - Hammer use to hammer nails, with "bionic" prosthetic hand, poses tricky Catch-22 for Cybathlon 2020 [review]}}, month = {April}, year = {2019}, url = {} }