Surgery – Truss – Pad
Patent
1987-04-10
1989-02-28
Coven, Edward M.
Surgery
Truss
Pad
307359, A61B 504
Patent
active
048076422
DESCRIPTION:
BRIEF SUMMARY
The present invention relates generally to devices for monitoring muscle tension and in particular the invention provides an improved device suitable for use in a work environment to monitor muscle tension of persons performing repetitive tasks and to provide a form of biofeedback, when training operators to minimize muscle tension while performing their allotted tasks.
Musculoskeletal pain in the workpiece (also called "Repetition Strain Injury", "RSI", or "Tenosinovitus" etc.) is currently a significant economic and social problem. Current opinion implicates the sustained low levels of muscle tension as the principal cause of musculo-skeletal pain, with repeated jerky movements being a secondary but still important cause of discomfort. If this condition is not attended to promptly it can also in some cases develop into a serious incapacity, which may effectively prevent an affected individual from following their chosen career.
For many years the method of electromyography (EMG) has been used to monitor muscle tension in the workplace and the information gathered by such measurements has been used to assess procedures in the workplace as well as the design of equipment used, and has proved to be of great value. However, a relatively unexplored use is as a method of training individuals to improve their workstyle. This involves the use of EMG equipment for "biofeedback", where the worker is given information about their muscle activity as they work in order that they may have the opportunity of trying different work methods and to determine quickly which of these methods produces the lowest muscle tension.
A small amount of work has been done in the area of work style biofeedback, both in Australia and overseas, however, a fundamental problem has existed to date in that the equipment used provides the person being trained with a large amount of irrelevant information, making their task of learning much more difficult. This situation has arisen largely because of the way in which the EMG signal is processed and presented to the user, the commonly used method of feedback being unsuitable for this particular purpose.
The EMG waveform is a rapidly fluctuating bipolar signal with an amplitude in the range of 1 to 1000 microvolts and a frequency in the range of several Hz to approximately 1 KHz. The signal in this application is picked up by adhesive surface electrodes placed on the skin covering the muscle whose activity is to be assessed and the signal produced by these electrodes is amplified and is also usually frequency limited to reject interference. The amplified signal is then rectified and passed through a low pass filter to extract the slowly varying (1 Hz or less) envelope of the wave form. It is this slowly varying wave form which has been shown to correlate highly with variations in muscle tension, and which is therefore used for workstation assessment and as the basis of biofeedback training. Most biofeedback EMG instruments process this signal further by comparing it to an adjustable threshold and displaying the difference on a meter or light bar display and may optionally also provide an audible tone whose frequency varies with the relative amplitude of the EMG signal. Usually when the EMG signal is smaller than the threshold level, no sound is heard, enabling the biofeedback device to be used as a "tension alarm", thus alerting the person being trained when their muscle activity exceeds a preset level. This type of signal is certainly of benefit in the case of muscles whose tension rises only when the person becomes too tense, such as with a person who is being trained to perform deep muscle relaxation in a clinic where they are not actually doing anything or performing a simulated work activity. However, real work involves occasional large movements which upset the operation of these simple EMG devices, such that if a typist reaches for a new sheet of paper, for example, the shoulder muscle tension will rise sharply, and the ordinary biofeedback instrument will produce a near maximum sound, wh
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Coven Edward M.
Lacyk John P.
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