Better Backs 2007 Speakers Notes – ULDs

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Slide 1

This presentation is part of the Better Backs Campaign 2007. The presentation will give you some background information on ULDs and help you better understand the questions in the ULD checklist that comes in the stakeholder pack.

Slide 2

Upper Limb Disorders (ULDs) is not a widely used term.  It is merely descriptive of where these aches and pains are in the body. There is no single disease called “ULD”. And in fact there are over 40 recognised complaints that might be called a ULD.

This presentation covers some of the risk factors associated with ULDs;  and some of things to look out for when using the check list. 

Slide 3

ULDs are best thought of as Disorders of the tissues of the upper limbs.  The vast majority of these complaints are non-specific – that is the symptoms do not form part of recognised illness – and most of them will go away in time.  Some complains are symptomatic of an illness – e.g. vibration white finger – and if the pain persists then a doctor should be consulted.

Slide 4

These are some names by which ULDs are known.  Work-related Upper Limbs Disorders (which means the person thinks work could have caused the pain and certainly makes it worse).  RSI, Repetitive Strain Injury usually used in connection with keyboards.  Cumulative Trauma Disorders and Occupational Overuse Syndrome are descriptive of what the doctor thinks has happened.  MSD is Musculoskeletal Disorders, less specific than work-related MSDs, WRMSD the last on the list.

Slide 5

This is HSE’s priced publication.  It is the most comprehensive guide to preventing and controlling ULDs in the workplace. There is a free leaflet Aching Arms.  The ULD checklist in the stakeholder pack concentrates on the 3rd and 4th steps – assessing and reducing the risks.  This presentation covers that area as well.

Slide 6

When assessing manual handling or ULD risks in the workplace a useful thing to remember is TILE – Task, Individual, Load and Environment.  Although moving heavy loads can cause ULDs, they are better assessed as manual handling risks, so Load is not looked at when considered ULDs themselves. 

Slide 7

These figures show that in simple terms, the larger the joint / muscle group, the lower the frequency of movements which can be tolerated without increasing the risk of injury – for example, if a worker had to flex or raise their arm at the shoulder at the same rate as say someone moves their fingers using a keyboard, they would quickly develop pain in their shoulder, whereas in the fingers, that higher frequency is tolerated.

Slide 8

Fixed posture relies on constant muscle use to hold it.  This can lead to restricted blood supply and a build – up of waste products. It can also cause joints to stiffen if pre-existing conditions are present.

Slide 9

Awkward postures can strain muscles and joints simply to achieve them. Awkward postures – or in fact any posture away from neutral – reduces the available maximum strength capabilities. So any force exertion becomes a greater percentage of maximum strength the further you move away from a neutral posture. And the greater the percentage of available strength which is used on a repetitive basis, the greater the risk of injury.

A nice simple example of how this works – get people to put their forearms out straight and with neutral wrist grip a pencil as hard as poss. Now get them to flex the wrist (bend hand backwards) and whilst flexed grip as hard as possible – it will be clear to people that they cannot grip as hard and it soon becomes uncomfortable at the carpal tunnel. This illustrates how movement away from neutral reduces available strength.

Slide 10

Forces have effects on the various elements of the Musculoskeletal system

It can be difficult to measure force exerted during upper limb intensive tasks (e.g. how do you measure the pinch force a sewing machinist uses to grip fabric). Sometimes it is possible though, if not the new ART tool has a straightforward graph to estimate forces. It will rely on asking workers how much effort is needed to do their tasks.

Slide 11

Forces - if excessive for the posture which is adopted during use can cause muscles to tear. Intensive use can cause tiredness and soreness and it is important people allow sufficient time to recover this. It results from small tears and / or lactic acid build-up in the muscles due to restricted blood flow.

Tendons pass through areas where joint use causes them to rub against surrounding tissues. In normal course of events we are designed to tolerate this. In cases of overuse, the tendons and the tendon sheaths become damaged by the continual contact and friction. Posture is again an important element in this – think back to gripping exercise, in the off-neutral position, pain was caused by tendon under tension pressing against carpal tunnel, if movements are added into the mix, potential for injury.

Inflammation of tendon tissues and muscles through overuse etc. can cause them to impinge on important nerves. The pressure on the nerves can result in pain and loss of sensation.

Slide 12

As a general rule of thumb, these are the forces which can be treated as guideline figures. Obviously the detail of the type of movement will be important – but these are the figures we can generally think in terms of for movements / actions generated by joints and muscle groups from the elbow ‘down’ (to the fingers).

Slide 13

Short frequent breaks should allow for tissues to recover and relax before any ‘tipping point’ is reached in build up of inflammation / waste products / micro-tears etc. Longer work periods risk creating damage which cannot fully recover even during a longer rest break, resulting in people starting to work again after their break - from an already less than ideal situation.

Slide 14

This was an example of a study in which a short frequent rest break regime was tested. The new system gave hourly breaks of 9 minutes. This led to reduced discomfort for the lower extremities and better sustained production rates (indicating that fatigue was being controlled better).

Slide 15

A range of environmental factors can affect upper limb risk levels.

Excessive cold can restrict blood flow to muscles – so less available energy / strength, and less efficient removal of waste products. This can cause reduced grip – so people will effectively need to grip harder (using a greater percentage of their strength).

Another risk could be created by wearing gloves.  Gloves increase the force that workers need to apply through their hands to achieve the same grip efficiency.

Vibration is another significant risk factor – it can cause grip forces to increase (to achieve better control and to reduce immediate surface discomfort) – it is strongly associated with CTS.

Poorly arranged lighting can cause people to stoop or lean forwards / to one side, adopting poor static postures to compensate and see as clearly as possible the work items.

Slide 16

When someone lacks control over the speed at which they have to work there are psychological and physical implications.

Physically it can result in a lack of variation in movement frequencies, and if machines are poorly set up, it can result in excessively high work rates.  Involving staff in the design or redesign of the workplace if possible when an opportunity arises can eliminate this problem.

Psychosocial factors such as poor social interaction with co-workers or a lack of co-operation with managers or poor management-worker relations are linked to a greater incidence of ULDs and increased chronicity (longer sickness absences)

Long shifts and overtime can cause people to build up injuries simply through greater exposure to the risks

Slide 17

Individual factors are very important.

One key issue is that new employees may need to build up their strength in order to do work without over-exerting themselves. The strength they need may be quite task specific so they may need to be phased into work. This also applies to competence and skill level – as people become more skilled and competent they may be able to develop and use techniques which reduce the amount of exertion needed to do tasks.

Body size is important in relation to workstation design – for example tall people at a fixed workstation may need to flex their heads forwards at a more pronounced angle to view the work items. On the other hand shorter workers may need to work with their upper arms raised for extended periods if the work surface is too high for them

Vulnerable groups (preganant or young workers) may need to have special risk assessments carried out to determine if they are more at risk. For example in later stages of pregnancy, posture can be compromised as someone may need to stand further from work items. Younger workers will be at particular risk from the factors explained in relation to competence, experience and skill level. They may also be less willing to take the initiative and adapt work situations themselves to make jobs easier and be less willing to report their symptoms early on.

People with previous injuries and pre-existing musculoskeletal conditions may be particularly at risk. The reason why certain individuals may be predisposed to MSDs are not clear-cut.  It may be related to joint structure / strength etc.

Slide 18

Multiple risk factors work together to create an overall level of risk. In particular physical and psychosocial risk factors exacerbate each other and have been shown to be linked to a greater risk of injury.

Slide 19

These points are fairly self explanatory. These are the factors that a ULD risk assessment should look at.  They have been grouped into TILE – a mnemonic used for assessing MSDs with Force replacing Load.  

Slide 20

So far we have looked at the risk factors in tasks that can cause problems for workers. The last few slides give some guidelines and suggestions about changes that could be made to the work environment, if your assessment indicates there are problems. 

The first thing to take into account is the limitations of the human body.  The place where people work should be adapted to them and the task they do. 

Work surface height is one of the most important ergonomic factors. This slide shows work surface heights and recommended ranges for different types of work – earlier on we talked about what is considered light / moderate forces etc. The recommendation is that the lighter and more precise the task is the higher the work surface should be. Heavier work tends to require higher forces which, particularly for vertical force direction, can be applied more easily if the surface is below elbow height. Light work is done higher up as it tends to be finer in detail requiring better visual accuracy. In addition finer control may require the arms and fingers to work on the task for longer and the higher surface gives a neutral position to the forearms. 

Slide 21

Reach distances can cause discomfort and shoulder problems if they are excessive for the frequency of action and the forces being applied. This diagram illustrates the functional normal and maximum reach distances which are recommended. Where items are positioned in the work area should depend on how often they are used and the forces required.

Slide 22

The last two slides gave the information you needed to improve the layout of a work station.  Make sure the working height is appropriate to the sort of work being done.  Look at how far the person has to reach for each task and put the most used equipment closer to them.  Use deflectors on conveyors so that workers have some control over the speed they work.

Slide 23

Lighting as mentioned previously, important in helping operators maintain good posture. Similarly, jigs / lifting work surfaces etc can also allow work items to be positioned where they can be easily viewed and worked on.

Good tools which are well maintained are essential: By tool, could mean anything from a knife to a power drill. Both of those also happen to be examples of tools where maintenance is highly important (e.g. to maintain knife sharpness to keep gripping forces as low as possible, or to maintain / replace drill bits to prevent operators having to push to help force drill through work item). Tools shouldn’t be excessively heavy if they are held frequently or continuously for long periods

Slide 24

If the work rate is machine / line paced and workers have no control over it, this can be a problem physically and mentally for operators.  They may be unable to give themselves natural breaks when they begin to feel fatigue. Ideally work should not be machine paced or it should be paced at a rate which does not strain workers / allows breaks etc. The slide gives some suggestions for changes.

Limiting forces – sometimes in production or packing tasks, workers will try to perform several duplicate task cycles at the same time e.g. waiting for several items which need to be handled in the same way and doing them all together. This will inevitably come down to a force frequency trade-off, but it should be examined whether multiple task cycle working is putting people at risk and whether it can be controlled, if need be.

Slide 25

A reminder of the HSE priced publication shown on slide 5 which contains HSE’s wisdom on ULDs.  There is also Aching arms, a free publication available as a pdf on this CD.  Another very popular publication is Working with VDUs also downloadable from this CD.  And don’t forget A pain in your workplace HSG121, which contains solutions to some upper limb intensive tasks.

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