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Hard Bimanual Activities (HBM) [overview]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Hard Bimanual Activities (HBM) [overview]; published August 12, 2015, 20:26; URL: https://www.swisswuff.ch/tech/?p=5330.

BibTeX: @MISC{schweitzer_wolf_1561457470, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Hard Bimanual Activities (HBM) [overview]}}, month = {August},year = {2015}, url = {https://www.swisswuff.ch/tech/?p=5330}}


Hard manually hazardous work as unfortunate requirement to arrive at "overuse"

After reading research presented at the ISPO 2015 in Lyon, France, that contends that "overuse" is regarded as consequence of not having a flexible prosthetic wrist unit (link) and that texting is the apparent cause for "overuse" in arm amputees based on somewhat questionable data (link) and after reading that they now are trying to reduce "overuse" through quantification of compensatory motions in the clothespin test by having an amputee report "overuse" after placing clothespins (link), it occurred to me that the authors of these studies, and most likely most researchers in that field, lack tangible experience and knowledge as to what in fact constitutes manual work that lends itself to actual "overuse" (rather than normal strain that happens after a somewhat unusual but quite singular very light weight activity that equates to lifting a fork, a spoon or possibly a tiny plastic clothespin).

Overuse usually denotes problems of the order of magnitude that makes you cringe, cry out in pain, and despite being a really hard bugger, seek therapy. That, in a nutshell, is overuse. And let us be clear here - as opposed to clothespins or toy relocation, there do exist bi-manual tasks that, in fact, are so strenuous that they do require the particular support of a prosthetic arm. Not that the industry is rushing to build these arms - no. But the problem exists. And they should build such arms.

As I work in a field that contains a whole number of significant manual everyday risks (as further outlined below), and as I worked hard towards building and getting built a prosthetic arm that actually helps rather than impedes for situations of real overuse, I have direct experience in "hard work". Others have that experience too, and many of these also resort to body powered arms to solve their situations.

Quite possibly one of the issues for "academic research" is that these researchers never actually researched the term "overuse" themselves, or, because they never considered that an arm amputee would perform actually hazardous (see below) manual work, and of course, because they never read up on all things related to hard and extensive "manual work" and furthermore, because they quite likely never performed such activities regularly and repeatedly themselves and thus stand absolutely no chance of actually knowing "first hand" what, in essence, "hard manually hazardous work" means, entails, and requires. Also, in terms of prosthetic arms, training and regeneration.

There thus must be a sociological reason why one tries to perfect the motors and sensors of a prosthetic hand to hold a single olive without squeezing it, but why one denies and rejects any work towards developing prosthetic arms for those that just want to load hay all afternoon in summer heat at 40 degrees Centigrade.

Images (C) Copyright Cybathlon / ETHZ

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ETH Cybathlon rehearsal at the Swiss Arena in Kloten, Switzerland, July 14th 2015. (ETH/Alessandro Della Bella)

Way to go!

Hard work is probably so different, so much different, from what is done in academic research, that we effortlessly understand why I always say that arm amputees and insurances on one hand, and academic researchers on the other hand, live on totally different planets, in worlds that have no overlap - which also explains why there is really no dialogue.

Try working outside in summer (link).

Try scrubbing toilets (link).

Images (C) Copyright Wolf Schweitzer

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And, no. I am not alone in scratching my head here, how it came about, that some fine ladies and gentlemen do just not seem to work harder. In fact, insurance representatives and rehabilitation specialists alike wonder why that is, too. Probably for sociological and industrial reasons.

What are activities that are likely to cause overuse? What activities are therefore particularly relevant for a prosthetic arm to assist with?

The list of activities that are paraded around to sell "bionic" arms is long and funny, and usually does not cover any truly bi-manual things.

Overuse is not explained by any fancy list of, say, carrying a tray with some bits and pieces on it, or, hanging one bit of laundry for 3 minutes or so, or holding on to a bottle of beer or so.

None of that requires a prosthetic arm, either. But, cheers if you can sell that to the clients anyway!

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Here, we should address what I call real work, and, coincidentally, what others call real work. That is what I require the prosthetic arm for, what I need it for, what the prosthetic arm is indispensable for.

It is important to see actual hard work aspects, before discussing the requirements for prosthetic arms that have to be met, in order for these prosthetic arms to reduce overuse.

References

The text below was not invented by me, but instead, it heavily cites, per-uses and reflects content and text from these sources:

This is to prevent all of y'all from saying that I just made it all up.

Overview of particularly hazardous manual work activities

Manual handling that risks to particularly strain an asymmetric body and that risks to particulary cause overuse of a single upper extremity in an arm amputee means:
- repetitive or sustained application of force
- repetitive or sustained awkward posture
- repetitive or sustained movement
- application of high force
- exposure to sustained vibration
- handling of live people or animals
- handling of loads that are unstable, unbalanced or difficult to hold

Forces, postures, movements and vibration usually affect each other.

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For example, more force has to be exerted to pick up a load from the floor while bending over compared with picking it up from a bench at thigh height.

A vibrating hand-tool generally requires more force to use than one that doesn’t vibrate.

And more effort is required to handle an object with the fingers wide apart than when they’re closer together

Repetitive application of force

Repetitive application of force means using force repeatedly over a period of time to handle, manipulate, move or support an object. For example:
- lifting and stacking goods onto a pallet
- gripping and handling bricks when bricklaying
- using a nail gun to fix palings to a fence
- pressing a pedal or button to operate a power press
- typing and other keyboard tasks

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For typing, posture is best using a hook, and weight distribution is by far the best using a hook. Your mileage may vary.

Sustained application of force

Sustained application of force occurs when force is applied
continually over a period of time. For example:
- pushing or pulling a trolley around hospital wards
- holding down a trigger to operate a power tool
- supporting a plaster sheet while fixing it to a ceiling
- supporting a patient walking down a corridor
- continuing to hold a tool when not using it

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Repetitive or sustained awkward posture

An awkward posture is one in which any part of the body is in an uncomfortable or unnatural position.

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Repetitive awkward postures include:

  • reaching sideways to pick up goods from a conveyor belt and pack them
  • picking up items from a conveyor belt and turning them over for inspection and packing

Sustained awkward postures include:

  • crouching to service plant or a vehicle
  • lying underneath a vehicle and reaching upwards to service it
  • kneeling while trowelling concrete or laying carpet
  • leaning over a low bath while bathing a patient
  • continually standing while operating a power press with foot pedal controls

Repetitive or sustained movement

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Repetitive or sustained movement means using the same parts of the body to repeat similar movements over a period of time. Examples of tasks involving repetitive or sustained movement include:

  • painting
  • lifting goods from a conveyor belt and packing them in a carton
  • typing and other keyboard tasks
  • assembly work in manufacturing
  • using a socket and ratchet or spanner to unscrew long bolts

Application of high force

Application of high force occurs in any task that either most people, or the employees likely to do the task, would find difficult because of the effort it requires. For example:

  • lifting or carrying a heavy object
  • pushing or pulling an object that is hard to move
  • operating tools with squeeze grips that are too far apart
  • throwing or catching objects
  • lifting a heavy item from a high shelf

Look out for any tasks that your employees describe as very physically demanding. If an employee needs help to do a particular task, or if you have assigned a stronger person to do the task, this indicates that the task requires the application of high force.

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Exposure to sustained vibration

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Vibration transferred from tools or machinery to the operator’s body can increase the risk of musculoskeletal disorders. Exposure to sustained vibration occurs in tasks such as:

  • using impact wrenches, chainsaws, jackhammers, grinders, drills or vibrating plates
  • operating earth-moving plant
  • driving a tractor
  • riding a bicycle, particularly, fast downhill offroad riding

Handling of live people or animals

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Handling of live people or animals is hazardous because their movements can’t always be anticipated. As a result, very high accelerations or "jerky" movements may cause overload to muscles and tendons. Examples include:

  • assisting a rehabilitation patient to walk down a ramp into a swimming pool
  • treating a panic-stricken animal in a veterinary clinic

Handling of loads that are unstable, unbalanced or difficult to hold

Loads that are unstable or unbalanced can move or change shape suddenly, or are uneven and heavier on one side. Loads that are difficult to hold include loads that are very large, slippery, floppy, sharp, hot, cold, toxic or unpleasant. Carrying a tray with a bit of food on it is not hard. But carrying a very long and heavy furniture part box may very well be hard.

For example:
• lifting a sack of flour
• carrying an open cooking pot full of soup
• carrying a large sheet of plasterboard
• carrying a laundry bag full of dirty linen

Repetitive or sustained postures and movements

Different types of postures and movements can contribute to musculoskeletal risks if they are repetitive or sustained. Generally, as the pace of work increases, postures and movements become more repetitive. As a general guideline, repetitive means done more than twice a minute, and sustained means held for more than 30 seconds at a time.

Tick YES on the risk assessment worksheet if the task requires any of the following to be done more than twice a minute or for more than 30 seconds at a time:

  • twisting the back more than 20 degrees
  • backward bending of the back more than 5 degrees
  • bending the head forwards or sideways more than 20 degrees
  • twisting the neck more than 20 degrees
  • bending the head backwards more than 5 degrees
  • bending the back forwards or sideways more than 20 degrees
  • reaching behind the body
  • squatting, kneeling, crawling, lying, semi-lying or jumping
  • working with one or both hands above shoulder height
  • reaching forwards or sideways more than 30 cm from the body
  • standing with most of the body’s weight on one leg
  • twisting, turning, grabbing, picking or wringing actions with the fingers, hands or arms
  • working with the fingers close together or wide apart
  • very fast movements

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Repetitive or sustained forces

Forces can contribute to musculoskeletal disorder risks if they are repetitive or
sustained. Generally, as the pace of work increases, forces become more repetitive. As a general guideline, repetitive means done more than twice a minute, and sustained means done for more than 30 seconds at a time.

Tick YES on the risk assessment worksheet if the task requires any of the following to be done more than twice a minute or for more than 30 seconds at a time:

  • lifting or lowering
  • carrying with one hand or one side of the body
  • exerting force with one hand or one
    side of the body
  • pushing, pulling or dragging
  • gripping with the fingers pinched together or held wide
    apart
  • exerting force while in an awkward posture
  • holding, supporting or restraining any object, person, animal or tool

 

Does the task involve long duration?

You have examined the repetitive or sustained postures, movements and forces that are present in the task. The next step is to look at the duration of the task. The duration of the task is how long the task is done for over a whole shift or continually at any time during a shift. Tick YES on the risk assessment worksheet if the task is
done for more than 2 hours over a whole shift or continually for more than 30 minutes at a time. In the comments section of the risk assessment worksheet, note
any aspects of the task that are causing it to be done for more than 2 hours over a whole shift or continually for more than 30 minutes at a time.

Does the task involve high force?

A manual handling task that involves high force is one that either most people, or the employees likely to do the task, would find difficult because of the effort it requires. High forces can be MSD risks even if they are not repetitive or sustained. This means that any task involving high force must be assessed as a risk, even if it is only done occasionally or for short periods. The longer and more often high force is
applied, the greater the risk. Some high force tasks involve the whole body – for example, lifting, lowering and carrying heavy weights. Other high force tasks involve only some parts of the body, such as the hands and arms.
Tick YES on the risk assessment worksheet if the task involves any of the following high force actions:

  • lifting, lowering or carrying heavy loads
  • applying uneven, fast or jerky forces during lifting, carrying, pushing or pulling
  • applying sudden or unexpected forces (for example, when handling a person or animal)
  • pushing or pulling objects that are hard to move or to stop (for example, a trolley)
  • using a finger-grip, a pinch-grip or an open-handed grip to handle a heavy or large load
  • exerting force at the limit of the grip span
  • needing to use two hands to operate a tool designed for one hand
  • throwing or catching
  • hitting or kicking
  • holding, supporting or restraining a person, animal or heavy object
  • jumping while holding a load
  • exerting force with the non-preferred hand
  • two or more people need to be assigned to handle a heavy or bulky load
  • during the application of high force, the body is in a bent, twisted or otherwise awkward posture

Tick YES on the risk assessment worksheet if any of the following information is reported about the task:

  • pain or significant discomfort during or after the task
  • the task can only be done for short periods
  • stronger employees are assigned to do the task
  • employees think the task should be done by more than one person, or seek help to do the task
  • employees say the task is physically very strenuous or
    difficult to do

Is there a risk?

The task involves a risk of muscoloskeletal order if the task involves repetitive or sustained postures, movements or forces, and it involves long duration, or, if the task involves high force.

Are environmental factors increasing the risk?

If a manual handling task involves a risk of musculoskeletal disorders, environmental factors can increase that risk. Environmental factors include
vibration, heat and cold.

Vibration

One can be exposed to two types of vibration: hand/arm,
and whole-body. Hand-arm vibration can occur when using vibrating tools or
equipment such as:

  • chainsaws and other mechanised saws
  • impact tools, including jackhammers, vibrating plates, chippers and pavement breakers
  • digging tools, including spade and ditch diggers and small augers
  • hand-tools, including pneumatic nut runners, impact wrenches and grinders
  • lawnmowers and brushcutters

Whole-body vibration occurs when the employee is seated or standing in plant or equipment such as:

  • tractors and heavy transport vehicles
  • cranes, forklifts and road-making plant
  • ride-on mowers and skid-steer loaders

Operating this kind of plant may also expose the employee to hand-arm vibration if the controls of the plant are vibrating as well.

Heat and cold

Your employees will be at greater risk of musculoskeletal disorders if they carry out
the manual handling task while exposed to:

  • high air temperatures (for example, in foundries, laundries, bakeries, kitchens, or working in hot weather)
  • radiant heat (for example, from the sun or from processes such as smelting or plastics extrusion)
  • high humidity caused by processes such as steam cleaning or the weather
  • low temperatures (for example, in cool rooms, cold stores, or working outside in cold weather)
  • Employees may also be at increased risk when:
  • wearing heavy protective clothing while working in hot conditions
  • wearing thick clothing that restricts movement while working in cold conditions (for example, gloves)
  • handling very cold or frozen objects
  • working in hot conditions if they are not used to it

Generally, the more boxes you tick on the risk assessment worksheet, the greater the risk. Similarly, the more often the task is done, or the longer it is done for, the greater the risk. Risk is also increased by the presence of environmental factors. In addition, a report of musculoskeletal disorder associated with the task usually indicates increased risk.

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It’s important to bear in mind that the above are general guidelines only. Manual handling occurs in a wide range of tasks and workplace situations, and muscoloskeletal disorders may be caused by a number of factors. For these reasons, some employees may be at risk even when working within these guidelines.

You must control any risks that you have found.

Examples

Risk assessment example 1 – Stacking boxes onto a pallet

Sue picks up boxes from a conveyor and stacks them onto a pallet on the floor at the rate of 5 boxes every minute. Because of the position of the conveyor and the pallet, Sue has to bend and twist her back more than 20 degrees each time she handles a box. She also has to reach forwards and sideways more than 30 cm from the body to do the task. She does this continually for 50 minutes. The task is done in a large, open warehouse near an outside loading bay.

Step 1a Does the task involve repetitive or sustained postures, movements or forces? Yes. The task involves bending and twisting the back, and reaching forwards or sideways more than 30 cm from the body. The task requires these actions to be done more than twice a minute (that is, 5 times a minute).

Step 1b Is the task done for more than 2 hours over a whole shift or continually for more than 30 minutes at a time? Yes. The task is done continually for 50 minutes at a time.

Step 2 Does the task involve high force? No.

Step 3 Is there a risk? Yes. The task is assessed as a risk because it involves repetitive and sustained postures and movements, and long duration (yes in step 1a and 1b).

Step 4 Are environmental factors increasing the risk? Because the task is done near an outside loading bay, how hot or cold it gets depends on the weather. During hot and cold weather, the risk will increase.

Risk assessment example 2 – Word processing

typingfast

Ahmed’s job involves word processing at a computer. The papers he is reading from sit flat on the desk, requiring him to bend and twist his neck more than 20 degrees to read them. Because of reflections in the computer screen and anuncorrected visual problem, Ahmed juts his chin forwards and bends his head backwards more than 5 degrees to read the screen. The height of the keyboard causes him to bend his
wrists backwards while typing. He spends about 4 to 5 hours a day word processing and often works continually for more than an hour at a time.

Step 1a Does the task involve repetitive or sustained postures, movements or forces? Yes. The task involves bending and twisting the neck, bending the head backwards, and bending the wrists. All of these actions are done for more than 30 seconds at a time.

Step 1b Is the task done for more than 2 hoursover a whole shift or continually for more than 30 minutes at a time? Yes. The task is done for 4 or 5 hours a day, and also for more than 30 minutes at a time.

Step 2 Does the task involve high force? No.

Step 3 Is there a risk? Yes. The task is assessed as a risk because it involves repetitive and sustained postures and movements, and long duration (yes in step 1a and 1b).

Step 4 Are environmental factors increasing the risk? No.

Risk assessment example 3 – Cleaning rooms in a hotel

Damien cleans 7 to 8 rooms in a hotel during a shift. The task involves vacuuming the room, cleaning the bathroom and making the beds. The beds are heavy, queen-sized beds, and must be pulled across the room for vacuuming.

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Step 1a Does the task involve repetitive or sustained postures, movements or forces? Yes. The task of cleaning the rooms requires the postures, movements and forces in the table below to be done more than twice a minute or for more than 30 seconds at a time.

Step 1b Is the task done for more than 2 hours over a whole shift or continually for more than 30 minutes at a time? Yes. Damien cleans rooms for more than 2 hours a day.

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Step 2 Does the task involve high force?Yes. Damien has to move each bed away from its position in the room to vacuum under it, and then move the bed back again. Because the beds are hard to move, this task involves
high force. Damien also has to bend and twist his back while using high force to move the bed.

Step 3 Is there a risk? Yes. The task is assessed as a risk because it involves repetitive and sustained postures, movements and forces, and long duration (yes in step 1a and 1b). It is also assessed as a risk because it involves high force (yes in step 2).

Step 4 Are environmental factors increasing the risk? No.

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Risk assessment example 4 – Loading a roll of plastic film on a wrapping machine

Jim operates a wrapping machine. Once in each shift, he fits the machine with a new roll of wrapping film. To do this, he must pick up the roll of film, which weighs 22 kg, from the floor, and lift it over a conveyor belt to its position at about head height on the wrapping machine.

The only access is from the front of the machine and Jim needs to twist to fit the roll. The diameter of the roll is 70 cm, and the width 30 cm, making it too big to hold close to the body when lifting. Jim finds the task very difficult and has tried to get assistance with the lift, but there is no room for a second person to fit in front of the machine because of the angle of the conveyor.

Step 1a Does the task involve repetitive or sustained postures, movements or forces? No. It’s done once a shift and takes less than 30 seconds.

Step 1b Is the task done for more than 2 hours over a whole shift or continually for more than 30 minutes at a time? No.

Step 2 Does the task involve high force? Yes. The roll is heavy and has to be lifted from the floor while bending forward. It must be positioned while in an awkward and twisted posture, with the load at arm’s length and head height. Access to the machine is blocked by the conveyor belt. All employees who have performed this task find it very difficult and strenuous.

Step 3 Is there a risk? Yes. The task is a risk because it involves high force.

Step 4 Are environmental factors increasing the risk? No.

How to improve resistance to hard work and to hazardous manual tasks

Resistance to hard work with hazardous manual tasks can be improved. Alone that however usually is greatly aided by a suitably built prosthetic arm - one that also withstands heavy (manufacturers, academics: I probably mean "extreme") activities.

  • Build core strength.
  • Build extremity coordination and balance.
  • Build proprioception and speed.
  • Build technical skills.

Once I started to swim serious butterfly, many "overuse" problems had only become an issue when I would perform hard work for days without break - not when I would clean the house or just paint a fence or so.

Both preparing for hard manual work, and conducting hard manual work, requires a suitably sturdy and reliable prosthetic arm.

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