| Introduction |
Four causes for too much force at work are
(1) Pushing a tool too hard,
(2) Gripping too hard,
(3) Co-contraction, where agonist and antagonist muscles contract simultaneously
e.g. making a tense claw of the hand without gripping anything,
(4) Maintaining awkward posture.
Handwriting can show these faults
(1) Pressing hard enough with a pen to indent paper resting on a cloth,
(2) Gripping so the index finger-tip is bent back and the skin blanches
over it (Fig 1a,b.),
(3) Co-contraction, with hardened forearm muscles, and
(4) Writing low down on a blackboard, with the wrist bent back forcibly.top
133 patients, clients of lawyers, and employees were referred with work-related pain in the arm and neck between 1982 and 1988 to a general surgeon with ergonomic interests.
Approximately 4500 other patients were treated in the same period, so this group constituted 3 per cent of the total. A former telegraphist was not a patient. Records were reviewed retrospectively in 1985 and again in 1988. With increasing experience, more details were recorded.
The main occupational groups were clerical and journalists (45), factory workers (38), and service workers in food, cleaning and sales (30). Others were switchboard operators, music teachers or students, and miscellaneous. The ones considered in this study are clerical, cleaners, and a labourer. In the clerical group the main factor related to pain was keyboard work in 35 cases and handwriting in 10 cases. top
Each record comprised information from other doctors and health workers, a clinical history, detailed job description, relevant examination, and progress notes. As the series grew, extra notes were made about techniques of work, as wells as results of the "Brachial Plexus Tension Test" for nerve compression in hunched neck postures (Elvey, 1981). Some cases were referred to rheumatologists, psychiatrists, and rehabilitation advisers.
Handwriting aspects noted were hand posture and how hard the writer pressed with a ball-point pen when writing on standard writing paper (75 gsm) resting on 8 thicknesses of a folded handkerchief. Observations were usually repeated a week later. Sometimes surface EMG studies were performed to help the patient understand the problem of excessive force applied.
A separate study of 23 different model of ball-point pen included measurements of how much force was needed to write legibly (3 to 25 g wt), to indent paper to different degrees (over 20 g wt) to tear it (over 60 g wt), and to make legible carbon copies (variable). Ink pens write with under 1 g wt.
In a few cases typing technique was assessed directly or by asking the patient to mime the actions of typing and observing the degree of wrist and finger extension, and by surface EMG. It was clear that dorsiflexion or ulnar deviation of the wrist when typing required much more activity of the forearm extensor muscles than with the wrist neutral or slightly flexed. top
Medical and psychological factors were managed appropriately, including further referral where indicated. Cases in whom Elvey's test (pinched nerves in the neck) was positive were advised about neck posture and exercises. Typists, writers, and musicians were shown the difference between tense and relaxed handwriting. Some typists were shown the effect on EMG of varying wrist posture. Writers were told of brands of pen which required little force to use. top
Of 35 keyboard workers, 25 were noted to write with excess force. 4 of the latter had neck problems or were seen and 8 were seen only once, leaving 13 cases treated and followed up. Of 6 who failed to improve, 4 were involved in protracted litigation, disputes at work, or had significant psychological problems, and the other 2 probably had psychological problems. The remaining 7 cases all improved to the point of cure following simple advice given. It is likely several of the cases seen only once also recovered. In 11 cases where Elvey's test was carried out (pinched neck nerves from bad posture), 8 were positive and 3 were negative.
All 10 clerks with pain from handwriting had a tense technique. Of this group, all except 2 lost their symptoms in one or two weeks. One was not followed up, and the other was angry with his employer over past events.
There were 2 cases of lateral epicondylitis. A work visit showed that a heavy commercial polishing machine had to be pulled up a step because there was no sloping ramp.
Two possible movement patterns (Fig 3) were defined.
(1) Keeping the elbow straight and balancing the machine on the step with the weight of the body (Fig 2a). This could be done with relaxed extensor muscles of the forearm.
(2) Bending the elbow slightly (Fig 2b). This posture was associated with strong contraction of the forearm extensors attached to the lateral epicondyle. Readers can confirm this by pulling on the edge of their seat with an open pronated grip of one hand while palpating the upper forearm muscle with the other hand, first with the elbow straight and relaxed, then with it bent.
A second factor was how nearly parallel the polisher was kept to the floor. Tipping it too much meant the operator had to "fight" the polisher and grip it more fiercely. Both cases were involved in litigation, and neither improved.
A third cleaner habitually kept the wrist flexed, whether holding a broom or a shopping bag (Fig. 3). top
Fig. 3
A male ex-clerk aged 36 developed pain in the forearms while cleaning tough grease from inside a large furnace with a chipping hammer. When asked to mime the technique he used, he pushed the hammer by extending the elbow with a short stroke and a stiff arm, instead of swinging in a loose movement including the shoulder. He resented his relegation from an office job (where there were some difficult inter-personal relationships) to a more menial and dirty task.top
At a local historic demonstration of telegraphy, two former operators showed distinct styles of hand-grip (Fig.4).
The operator with a tense grip, passively dorsiflexing the index and middle finger-tip, formerly had forearm pain when working. The operator with gently curled fingers had no such pain.top
Fig.4
All 4 in the series had unusually strong co-contraction when their handwriting style was tested.top
In this study, 15 out of 133 cases with work-related pain, or 11 per cent, had relief by relaxing their work habits. Incomplete follow-up means this success rate has been under-estimated.
Poor skill at work has received scanty recognition in theory or practice. A case of tenosynovitis in a shoe assembler, probably due to excessive force, was mentioned by Welch (1973), and 9 cases of work pain from tense habits were recorded by Patkin (1984), together with references to the condition in musicians.
Earlier writers on cramp in writers and telegraphists considered the muscular contraction to be involuntary. In this series conscious control was often possible. In sport and music it is common to re-train skilled movements to be more relaxed and efficient. Skill could be re-defined more broadly to include posture, choice of equipment at work, and its care. (An example is abattoir workers sharpening their knives). Review of the literature on skill is precluded by limited space. top
Tense work habits and other poor skills are a common cause of pain at work and can be remedied.top
Elvey RL (1981) Brachial plexus tension tests and the
pathoanatomical origin of arm pain, in Aspects of Manipulative Therapy,
Lincoln Institute of Health Sciences, Carlton, Australia
Patkin M (1984) Trying too hard, in Proc.21st conf. ESANZ, 298-301.
Welch R (1973) Ergonometrics of Tenosynovitis, in Occupational Injuries.
Seminar manual, Roy.Aust.Coll.Surg, 145-147.
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Contents
Material
Observations & methods
Treatment
Results
Keyboard workers
Writers
Cleaners
Using a hammer
Morse-key operators
Musicians
Discussion
Conclusion
References
Excess effort and pain at work:
the missing ergonomic factor,
Michael
Patkin, Whyalla, South Australia, in
Proceedings of the 2nd international conference of the International Ergonomics Association, Sydney, 1988
Abstract
Many people use excessive force at work and some of these develop pain. This study reports 44 cases using excessive force in 5 occupations. In 15 cases followed up, pain was relieved by advice on technique. All came from a series of 133 patients with occupational pain referred for treatment or medico-legal assessment.
This paper was presented at the 2nd international conference of the IEA (International Ergonomics Association) in Sydney, Australia in 1988.
This was during a time of national and international controversy, often bitter about whether RSI (Repetitive Strain Injury) was a physical injury, pscyhological or imaginary, or fraudulent.
My view, like that of some others, was that RSI was an unsatisfactory umbrella term for a number of different conditions, which could be identified by taking an adequate medical and personal history (including fine details of occupation and methods of work), and an adequate medical examination (including Elvey's test for brachial plexus tension, controversial and disputed by orthopaedists and neurologists)
I still think one of the major factors igrnoed is tense habits of work. For me a convincing demonstration was possible by merely feeling local tension in upper forearm muscle compared with the other side and by the more frequent beeping from a pocket-sized EMG (electromyograph) meter. This beeping could be demonstrated convincingly to an audience of 200 or more people at a time.
Seen over 15 years later my own dogma and prejudice shows later in this paper in the way I assert that patients not reviewed would obviously have been improved by the tretment described.
In an interesting aside the much maligned FW Taylor (of time and motion and Taylorism fame) said that labourers loading steel had to rest almost 50 per cent of their working day or they would suffer injury.
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