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Biomedical subjects

T J Armstrong

Publications and source records attributed to T J Armstrong.

63 records · Page 4Linked to original sources
PubMed1980

Static work elements and selected circulatory responses.

It has been recommended that circulatory responses be used as measures of circulatory stress and as a basis of work-rest scheduling. The purpose of this paper is to show how statistical models can be developed and used to describe selected circulatory responses associated with static work elements. Heart rate, mean arterial pressure and cardiac work were modeled as functions of work duration and intensity for four subjects performing sustained static group exertions to exhaustion at 12.5%, 25%, 50% and 75% of maximum strength. Examples and considerations of predicted circulatory responses to static work elements are discussed.

Blood Pressure↗
PubMed1980

Establishing an industrial strength testing program.

This study was performed to develop and evaluate a scheme for matching the strength of workers to the strength demands of their jobs. Biomechanical analyses were performed on production jobs in an aluminum reduction plant to identify and quantify strength demands. These data were used to design a set of nine strength tests which simulated job activities with the greatest strength requirements. A cross section of plant employees assigned to these jobs was strength tested and monitored for medical incidents for a period of over two years. Significant relationships were found among job strength requirements, worker strengths, and medical incidents. Workers with strength abilities (as determined by the tests) less than job strength requirements suffered a higher rate of medical incidents than workers whose strength abilities matched or exceeded job demands. It was concluded that strength testing can be used to identify workers who would be at increased risk of suffering medical incidents if placed on jobs which exceeded their strength abilities.

Adolescent↗
PubMed1980

Intraneural connective tissue proliferation of the median nerve in the carpal tunnel.

Segments from the median nerve were removed from the distal fourth of the right forearm and the carpal tunnel area of 23 embalmed human cadavers (12 men, 11 women) to evaluate the proliferation of the intraneural connective tissue and its intrinsic vasculature. The findings suggest that: (1) The proliferative increase of the intraneural connective tissue, primarily, the epineurial layers, is a localized characteristic of the median nerve in the carpal tunnel; (2) this increase in a normal occurrence in males and females; and (3) thicker-walled arterioles and venules are common in the highly dense epineurial tissue; this condition, regarded as an adjunct protective feature, could oppose increased intratunnel pressure and lessen the chances of vascular collapse.

Arterioles↗
PubMed1979

Carpal tunnel syndrome and selected personal attributes.

Carpal tunnel syndrome has been reported to occur between two and ten times as frequently in women as in men. It also has been reported that this syndrome is often associated with the performance of certain manual tasks. Such cases can be considered an occupational disease. This study was addressed to the question: Why do some people develop carpal tunnel syndrome while others do not? Two matching female populations, one with a known history of carpal tunnel syndrome and one without a known history of carpal tunnel syndrome, were selected and differences in hand size and work methods were studied. Both populations were employed in the same production sewing jobs. While differences in hand size were not found, use of forceful exertions and of deviated wrists and pinch hand position - particularly during forceful exertions - were found to be associated with carpal tunnel syndrome.

Adult↗
PubMedDate not supplied

The effects of keyswitch stiffness on typing force, finger electromyography, and subjective discomfort.

The effects of keyswitch stiffness and key action on typing force, electromyography (EMG), and subjective preference were examined. Each subject's own keyboard (with an audible key click and key activation force of 0.72 N) and three keyboards with no key click that were identical in design but had different key activation forces (0.28 N, 0.56 N, and 0.83 N) were used. Subjects (24 female transcriptionists) typed on each keyboard for 15 min while typing force and left hand surface EMG of the finger flexor and extensor muscles were monitored. Subjects then used one of the keyboards at their workstations for 7 workdays and were monitored again. This procedure was repeated for all four keyboards. Typing force and finger flexor and extensor EMG activity were highest for the 0.83 N keyboard. Lowest EMG values were for the 0.28 N and the 0.72 N audible key click keyboards. Baseline (10th percentile) and median (50th percentile) extensor EMG values were significantly higher than flexor EMG values. Peak (90th percentile) EMG values were comparable for flexors and extensors. Mean subjective discomfort was significantly higher for the 0.83 N keyboard at the fingers (36% higher), lower arm (40% higher), and overall (39% higher). Seventeen of 24 subjects preferred the 0.72 N keyboard, 4 the 0.28 N keyboard, and 3 preferred the 0.56 N keyboard. Results suggest that increasing make force causes typing force and EMG to increase but that the ratio of 90th centile typing force to make force decreases as make force increases. Subjective discomfort was significantly higher for the keyboard with 0.83 N make force. Buckling spring keyboards have better feedback characteristics, which may be responsible for a decrease in the amount of typing force and EMG produced.

Adult↗