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Thermal stress and human performance
apparent mass of the legs, to predict the transmissibility of the seat with a person. Good agreement was obtained between measured and predicted seat transmissibilities.
22.2.32 (119129)
Messenger, A.J., and Griffin, M.J. Lumbar support in seating: Effects on erector spinae muscle activity, posture and discomfort. In: E.J. Lovesey (Ed). Contemporary Ergonomics 1990, Taylor & Francis, London, 1990, pp 2 9 3 - 2 9 8 , 6 refs. Fourteen male subjects were asked to sit in a helicopter pilot's seat fitted with five alternative lumbar supports varying in thickness from 0 to 80 mm. Electromyographic (EMG) activity and back posture were measured and discomfort ratings obtained. Increasing the lumbar support thickness from 0 to 80 mm increased lumbar lordosis. The thoracic region of the erector spinae muscles appeared to be the most sensitive to changes in lumbar support thickness: increasing lumbar support thickness significantly reduced EMG activity. In the lumbar region of the erector spinae muscles, EMG activity was lowest with no lumbar support. Increasing lumbar support thickness produced few other significant changes but a general increase in muscle activity in the lumbar region. Ratings for discomfort in the lower back and overall discomfort was greatest with the 80 mm lumbar support.
22.2.33 (119133)
Gagnon, M., Lortie, M., and Roy, R. The evaluation of the friction characteristics of different piques used for handling patients. Int J of Indust Ergonomics, 1990, 5 . 2 , 1 6 1 - 1 6 8 , 11 refs. The objective of this work was to examine the friction characteristics of the pique used by nursing aides for handling patients. The pique has been associated with a large number of injuries. Mechanical tests were administered to evaluate three different types of pique, two conditions of wear and the interactions with different types of sliding surfaces (two types of drawsheet) and weights (two conditions). Both the static and dynamic friction coefficients were measured. Factorial analyses of variance showed that: (i) the performance o f the pique, preferred by nursing aides, was superior, and (ii) the sliding conditions affected the friction characteristics. Several validity questions are raised to show the risk of extrapolating results to practical situations.
22.2.34 (119135)
Kumar, S., and Cheng, C. Spinal stresses in simulated raking with various rake handles. Ergonomics, 1990, 33.1, 1 - 1 1 , 5 refs. Five young male subjects performed a simulated raking task by pushing and pulling 14 different rake handles at 60 N and 110 N simulated soil resistance in a random order. The raking action was performed at a selfselected uniform pace over a 60 cm stroke length with initial, middle and final phases marked. During this action the raking force and the angle of the rake was measured by a load cell and a p o t e n t i o m e t e r respectively. The posture was recorded with a video cassette recorder. The posture and force values were used for the determination of the spinal compression load. In rake pulling, the 13 modified rake handles generated a spinal compression of only 20% to 50% of the straight handle, whereas in rake pushing the modified handles generated compression up to five times that of the straight handle. The compression generated with the straight handle never reached the action limit, whereas those o f the 13 modified handles rarely stayed within the action limit. Therefore, a straight handle is considered the handle of choice.
Environment 22.2.35 (119912) Hussain, S.G., Arens, J.B., and Parsonson, P.S. Effect of light sources on highway sign color recognition. In: Human Performance and Highway Visibility. Design, Safety and Methods, b y the Transportation Research Board, National Research Council, Washington, DC. Transportation Research Record 1213, 1989, pp 2 7 - 3 4 , 3 refs. A wide variety of light sources is used for externally illuminated highway signs. Some of these light sources change the colour appearance of signs at night. This study evaluates acceptable alternative light sources for illuminating highway signs. Light sources investigated included incandescent, fluorescent, metal halide, mercury, high- and low-pressure sodium lamps. The metal halide lamp performed best overall and is recommended to illuminate a broad range of highway sign colours. This also could include the use of metal halide lamps in future automobile headlights. Mercury lamps that are economical and provide good colour rendition on green, blue and white are recommended for overhead signs. With some compromise on the colour rendition, highpressure sodium is another cost-saving
alternative for overhead signs. Highpressure sodium is also the best choice to illuminate construction and maintenance signs. 22.2.36 (119145) Levy-Leboyer, C. Noise effects on two industrial tasks. Work and Stress, 1989, 3.4, 3 1 1 - 3 2 2 , 27 refs Very little is known about the effects o f noise on the quality and quantity of m o t o r task performance, particularly in natural work settings. The present paper describes a study of the effects of noise on the performance of two tasks: the assembly of car carburettors and car air conditioners. The tasks were carried out either under quiet conditions (65 dBA) or noisy conditions (75 or 90 dBA): four broadly comparable groups of workers were studied. The data suggested, among other things, that all ' f a u l t y ' behaviours involving a mental load were affected by noise although manual dexterity was not. It also appeared that noise impaired activities involving visuo-motor co-ordination. These findings, and others, are discussed in terms of information processing. 22.2.37 (119927)
Kjellberg, A. Psychological aspects of occupational vibration. Seand J Work, Environ & Health, 1990, 16. Supplement l, 3 9 43, 33 refs. A short review is given of the subjective responses to vibration (primarily whole-body vibration) and of its performance and psychophysiological effects. The subjective importance of the basic physical vibration parameters and the effects of whole-body vibration on performance of tasks requiring manual control and visual acuity have been well covered by research, whereas knowledge of the effects on cognitive performance is rather meagre. 22.2.38 (119934)
Enander, A.E., and Hygge, S. Thermal stress and human performance. Scand J Work, Environ & Health, 1990, 16. Supplement 1 , 4 4 - 5 0 , 58 refs. There is evidence that the thermal stress encountered in many work environments may negatively affect various aspects of human performance and behaviour. Evaluation of the empirical research is, however, complicated by differences in both the m e t h o d o l o g y and the definition of the basic stimulus. Effects of heat and cold stress are briefly reviewed, with particular regard to theoretical considerations.
Applied Ergonomics Apri/1991
133
22.2.32 (119129)
Messenger, A.J., and Griffin, M.J. Lumbar support in seating: Effects on erector spinae muscle activity, posture and discomfort. In: E.J. Lovesey (Ed). Contemporary Ergonomics 1990, Taylor & Francis, London, 1990, pp 2 9 3 - 2 9 8 , 6 refs. Fourteen male subjects were asked to sit in a helicopter pilot's seat fitted with five alternative lumbar supports varying in thickness from 0 to 80 mm. Electromyographic (EMG) activity and back posture were measured and discomfort ratings obtained. Increasing the lumbar support thickness from 0 to 80 mm increased lumbar lordosis. The thoracic region of the erector spinae muscles appeared to be the most sensitive to changes in lumbar support thickness: increasing lumbar support thickness significantly reduced EMG activity. In the lumbar region of the erector spinae muscles, EMG activity was lowest with no lumbar support. Increasing lumbar support thickness produced few other significant changes but a general increase in muscle activity in the lumbar region. Ratings for discomfort in the lower back and overall discomfort was greatest with the 80 mm lumbar support.
22.2.33 (119133)
Gagnon, M., Lortie, M., and Roy, R. The evaluation of the friction characteristics of different piques used for handling patients. Int J of Indust Ergonomics, 1990, 5 . 2 , 1 6 1 - 1 6 8 , 11 refs. The objective of this work was to examine the friction characteristics of the pique used by nursing aides for handling patients. The pique has been associated with a large number of injuries. Mechanical tests were administered to evaluate three different types of pique, two conditions of wear and the interactions with different types of sliding surfaces (two types of drawsheet) and weights (two conditions). Both the static and dynamic friction coefficients were measured. Factorial analyses of variance showed that: (i) the performance o f the pique, preferred by nursing aides, was superior, and (ii) the sliding conditions affected the friction characteristics. Several validity questions are raised to show the risk of extrapolating results to practical situations.
22.2.34 (119135)
Kumar, S., and Cheng, C. Spinal stresses in simulated raking with various rake handles. Ergonomics, 1990, 33.1, 1 - 1 1 , 5 refs. Five young male subjects performed a simulated raking task by pushing and pulling 14 different rake handles at 60 N and 110 N simulated soil resistance in a random order. The raking action was performed at a selfselected uniform pace over a 60 cm stroke length with initial, middle and final phases marked. During this action the raking force and the angle of the rake was measured by a load cell and a p o t e n t i o m e t e r respectively. The posture was recorded with a video cassette recorder. The posture and force values were used for the determination of the spinal compression load. In rake pulling, the 13 modified rake handles generated a spinal compression of only 20% to 50% of the straight handle, whereas in rake pushing the modified handles generated compression up to five times that of the straight handle. The compression generated with the straight handle never reached the action limit, whereas those o f the 13 modified handles rarely stayed within the action limit. Therefore, a straight handle is considered the handle of choice.
Environment 22.2.35 (119912) Hussain, S.G., Arens, J.B., and Parsonson, P.S. Effect of light sources on highway sign color recognition. In: Human Performance and Highway Visibility. Design, Safety and Methods, b y the Transportation Research Board, National Research Council, Washington, DC. Transportation Research Record 1213, 1989, pp 2 7 - 3 4 , 3 refs. A wide variety of light sources is used for externally illuminated highway signs. Some of these light sources change the colour appearance of signs at night. This study evaluates acceptable alternative light sources for illuminating highway signs. Light sources investigated included incandescent, fluorescent, metal halide, mercury, high- and low-pressure sodium lamps. The metal halide lamp performed best overall and is recommended to illuminate a broad range of highway sign colours. This also could include the use of metal halide lamps in future automobile headlights. Mercury lamps that are economical and provide good colour rendition on green, blue and white are recommended for overhead signs. With some compromise on the colour rendition, highpressure sodium is another cost-saving
alternative for overhead signs. Highpressure sodium is also the best choice to illuminate construction and maintenance signs. 22.2.36 (119145) Levy-Leboyer, C. Noise effects on two industrial tasks. Work and Stress, 1989, 3.4, 3 1 1 - 3 2 2 , 27 refs Very little is known about the effects o f noise on the quality and quantity of m o t o r task performance, particularly in natural work settings. The present paper describes a study of the effects of noise on the performance of two tasks: the assembly of car carburettors and car air conditioners. The tasks were carried out either under quiet conditions (65 dBA) or noisy conditions (75 or 90 dBA): four broadly comparable groups of workers were studied. The data suggested, among other things, that all ' f a u l t y ' behaviours involving a mental load were affected by noise although manual dexterity was not. It also appeared that noise impaired activities involving visuo-motor co-ordination. These findings, and others, are discussed in terms of information processing. 22.2.37 (119927)
Kjellberg, A. Psychological aspects of occupational vibration. Seand J Work, Environ & Health, 1990, 16. Supplement l, 3 9 43, 33 refs. A short review is given of the subjective responses to vibration (primarily whole-body vibration) and of its performance and psychophysiological effects. The subjective importance of the basic physical vibration parameters and the effects of whole-body vibration on performance of tasks requiring manual control and visual acuity have been well covered by research, whereas knowledge of the effects on cognitive performance is rather meagre. 22.2.38 (119934)
Enander, A.E., and Hygge, S. Thermal stress and human performance. Scand J Work, Environ & Health, 1990, 16. Supplement 1 , 4 4 - 5 0 , 58 refs. There is evidence that the thermal stress encountered in many work environments may negatively affect various aspects of human performance and behaviour. Evaluation of the empirical research is, however, complicated by differences in both the m e t h o d o l o g y and the definition of the basic stimulus. Effects of heat and cold stress are briefly reviewed, with particular regard to theoretical considerations.
Applied Ergonomics Apri/1991
133