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Home Forums General Ergonomics Topics Lateral Epicondylitis and Forearm Pronation

This topic contains 26 replies, has 7 voices, and was last updated by  vino 16 years, 7 months ago.

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  • #37450

    admin
    Keymaster

    Is anyone aware of any research regarding the effect that forearm pronation has on lateral epicondylitis? I’m currently working with a female worker who will soon undergo a surgical resection/repair of her dominant elbow secondary to chronic lateral epicondylitis. She performs data entry for 50% of her work day (70% of the time using a mouse and 30% by keystroking on a standard keyboard)and handwriting tasks for 30% of her work day (on a flat surface).

    Also, is there any any research regarding writing style/instruments and lateral epicondylitis? Any assistance would be appreciated.

    #41430

    [private user]
    Participant

    Dear User:

    Its unlikely that her injury is just due to pronation. It’s more likely to be the finger flexion/gripping of the mouse and the whole arm compression that accompanies people working under time pressure. Environmental noise, auditory and visual also impact muscle compression.

    You could ask her to try moving the mouse to the other non-dominant side, with the accompanying changes to the keyboard tray, and/or provide a different type of input device, either a trackball or a touch screen surface.

    #41439

    broadwayergo
    Participant

    Please don’t also forget about the influence of the neck and shoulder girdle postural influences and the possiblity that there is an underlying radial tunnel syndrome. So look at whole body posture and work station fit as well as focusing on the hand and arm.

    #41446

    admin
    Keymaster

    Dear Colleague (User4366),

    Prolonged pronation can certainly cause muscle fatigue (and prolonged muscle fatigue can lead to overuse symptoms). My Masters thesis dealt with this topic. It can be found on the web at;

    http://www.goldtouch.com/about_rsi/ergonassesofkbd.pdf

    For this reason it is important to minimise the pronation due to prolonged mouse use. This article on pain from mousing might be of interest to you;

    https://ergoweb.com/news/detail.cfm?id=834

    A neutral posture is useful for minimising discomfort due to prolonged mouse work

    #41466

    [private user]
    Participant

    I would just like to point out a new treatment-alternative to surgical intervention; RSWT – radial shockwave therapy (http://www.ems.com or you search for “shockwave therapy”) has proven effective beyond cortison and made surgery 2nd choice in many cases.

    Rgds Roald Danielsen

    #41362

    vino
    Participant

    Pronation of the forearm enhances the muscle activity of the wrist extensors, especially at low forces, compared to a neutral position. There is also a gender difference: women produce a lower maximum force than men and require 5-10% MVC more of extensor activation at a force of 50 N. A link with musculoskeletal overload may be made.

    References:

    Mogk & Keir 2003. The effect of posture on forearm muscle loading during gripping. Ergonomics 46, 9, 956-75.

    O’Sullivan & Gallwey 2002. Upper-limb surface electro-myography at maximum supination and pronation? J Electromyogr Kinesiol 12 (4): 275-285.

    #41492

    admin
    Keymaster

    Do not understimate the potential success of good elbow support from the armrest of the chair when the worker is doing data entry and using the mouse. Proper armrest support eliminates static loading of the shoulder, neck, and forearm. Many times, especially with women of small stature, 50% and below, the armrest of the chair must be horizontally as well as vertically adjustable to prevent an abducted position of the shoulder. Additionally, if mouse and keyboard supports (preferrably gel) are not in place for support, there can be much more of a tendency to “cock the wrist” which not only causes more muscle activity at the lateral epicondyle, but activity of a longer duration than is necessary for the task. It doesn’t take equipment to detect when less muscle activity has been achieved, simple palpation of the lateral epicondyle while the worker performs the various task elements is adequate. Very often I will ask the worker to use the fingers of the other hand to palpate the difference on him/herself.

    Carole Hunter, MS, CPE

    Industrial Biomechanics, Inc.

    P.O. Box 35131

    Greensboro, NC 27425

    336-643-7706

    [email protected]

    #41505

    admin
    Keymaster

    Carole and co,

    Any of you who had trouble downloading my treatise as a PDF might be able to use this link to an HTML version;

    An Ergonomic Assessment of a Segmented Keyboard

    http://www.google.com.au/search?q=cache:NrU1dyZLdYUJ:www.goldtouch.com/about_rsi/ergonassesofkbd.pdf++%22segmented+keyboard%22&hl=en&lr=lang_en&ie=UTF-8

    Regards,

    David McFarlane

    Ergonomist,

    WorkCover Authority of New South Wales

    #41531

    admin
    Keymaster

    Is anyone aware of any research regarding the effect that forearm pronation has on lateral epicondylitis? I’m currently working with a female worker who will soon undergo a surgical resection/repair of her dominant elbow secondary to chronic lateral epicondylitis. She performs data entry for 50% of her work day (70% of the time using a mouse and 30% by keystroking on a standard keyboard)and handwriting tasks for 30% of her work day (on a flat surface)…

    Forearm pronation has minimal effect on lateral epicondylitis. There are only two muscles that pronate the hand (pronator teres and quadratus), neither of which have tendon attachments to the lateral epicondyle. There is a slight increase (but only slight) in wrist extensor activity when pronating with an unsupported hand due to these muscles needing to activate to stabilize/hold the hand in a neutral/functional position. These wrist extensor muscles DO connect to the lateral epicondyle. This increase in muscle activity is minimized with hand support. In an office/computer workstation environment, the most common contributing factor to the development of lateral epicondylitis (aka tennis elbow) is static wrist extension. This is most commonly seen with a mouse that is located too far away from the user, requiring an extended elbow and wrist to manipulate. If the keyboard is positioned too low or angled too high in the back (tilted toward the user), this can also require the wrist and digit extensor muscles (that all connect to the lateral epicondyle) to statically contract contributing to strain on the tendon attachment to the bone. I will politely disagree with the poster who suggested gel wrist supports for mousing. I typically see users “planting” their wrist or heel of the palm on these and using wrist ulnar and radial deviation (side to side motions) to manipulate the mouse. The muscles that ulnarly and radially deviate the wrist/hand also attach to the lateral epicondyle. The best solution is to position the keyboard to allow neutral wrist posture first. Then position the mouse directly next to the keyboard so that the upper arm can be held “at rest” by the side of the trunk and the wrist can be maintained in a neutral posture. For handwriting, you will want to provide a writing utensil with an enlarged grip (such as a “Dr. Grip”) to decrease pinch forces. Higher pinch forces (flexion) require higher muscle contraction of the antagonist muscles (the digit and wrist extensors) to stabilize the position of the wrist, again, potentially contributing to the strain on the tendon attachments at the lateral epicondyle. Can you post a link to a picture of the workstation in question???

    #41533

    admin
    Keymaster

    Dear User3541,

    I suspect (after reading the National Library of Medicine abstract) that the gripping exercises performed in the Mogk and Keir paper would have little resemblance to the tasks performed by the office worker that you mentioned.

    I have tracked down a paper by Zipp and colleagues that might be of interest to you. They found that measurements of muscular activity by electromyography (EMG) indicated that ulnar deviation of the wrist at angles greater than 20 degrees causes the EMG signal from an extensor muscle (Flexor Carpi Ulnaris) to rise exponentially (Zipp et al, 1983). My own research showed that a combination of wrist pronation and dorsiflexion (extension) are associated with a greater level of activity in the Extensor Carpi Ulnaris muscle which might cause rapid tiredness in that muscle. Reducing the amount of wrist pronation and flexion greatly reduced the level of activity in this muscle.

    Like they say – straighten up and fly right!

    Regards,

    David.

    Reference:

    Zipp, P. Haider, E., Halpern, N. & Rohmert, W. (1983), “Keyboard design through physiological strain measurements”, Applied Ergonomics, 14.2, 117-122.

    #41542

    admin
    Keymaster

    I have had a number of private replies that mention the term ‘keeping the wrist straight’. This phrase is so variously interpreted as to be meaningless (and its use should be avoided for that reason).

    What is desirable is to keep the wrist in the natural posture that is least tiring for the task at hand.

    Regards,

    David.

    #41547

    admin
    Keymaster

    I agree that the admonishment to ‘keep the wrist straight’ needs more definition, but what is the meaning of the ‘natural position’ and ‘least tiring’?

    #41550

    admin
    Keymaster

    Thomas,

    This has always been a matter of contention and for this reason the natural position of the wrist was shown in an illustration in the Australian National Code of Practice for the Prevention of Occupational Overuse Syndrome (National Occupational Health and Safety commission, 1994). This is on the web. It is at: http://www.nohsc.gov.au/PDF/Standards/OOS_COP_NOHSC2013_1994.pdf

    See clause 7.16 and figure 9.

    Its use for mouse work is illustrated in a photograph in my article (on the Human Factors and Ergonomics Society – Europe Chapter website) describing the results of my web survey on strategies for minimising discomfort in the wrist and lower arm due to prolonged mouse work. This can be found at: http://utopia.ision.nl/users/hfesec/newslet/resultsrsi.htm

    My masters research indicated that it is the least tiring position for keyboard work.

    As you can see from the photo I rest my wrist!

    Regards,

    David.

    #41551

    admin
    Keymaster

    Hello David,

    I agree with you and would generaly support the position on wrists in which you’re resting; but the problem with which I think that we’re wresting in regard to wrists is what position would we quantitiatively define as a “natural” or ‘straight’ wrist posture?

    For example, in what range of angles is the wrist posture ‘natural’; in what range of angles is the posture ‘straight’?

    Best regards,

    Tom

    #41552

    admin
    Keymaster

    Tom,

    If you were to ask a physiologist you would probably be told that the position of neutral rotation is where the palm faces medially (Kapandji, 1982). This might well be true but in office work this is almost never a functional position (most tasks

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