| Summary: | 碩士 === 國立臺北科技大學 === 工業工程與管理系碩士班 === 104 === Common scrubbing cleaning tasks usually associate with repetitive motion, awkward postures as well as high physical load. These risk factors make cleaning workers become a high-risk group of upper extremity musculoskeletal hazards. However, relatively few researches were focused on cleaning work in comparison with other occupations, and most of the relevant studies emphasized on improving the cleaning tool. So far, information about hand force required to operate different cleaning tools are still limited. This experimental study is to investigate the psychological and physiological load of participants conducting scrubbing tasks under combination conditions of 3 force levels and 3 surface heights, by using a long-handle brush and a sessile brush. A projector and 4 WiiFit balance boards were integrated to set up the control environment for simulation experiment. The WiiFit boards were placed on a hydraulic wheel cart with adjustable height to simulate different height of work surface. Each participant was asked to scrub on the boards using a long-handle brush or a sessile brush. The WiiFit boards continuously measured exertion forces and center of resultant force of each participant, sending the measured data to a computer via Bluetooth. The computer then controlled the projector to project color image onto the board surfaces to provide visual feedback. The images, originally black, turned whiter as the computer program continuously read in data and translated force magnitude into color depth and superimposed its “magnitude” onto the corresponding board location. The images finally turned green when the entire region reached the force setting level. Data collected in experiments include individual subject’s WiiFit board force brush handle force, upper extremity EMG, average heart rate, and VAS fatigue scale. All data were used to compare the workload difference in long-handle brush and sessile use and to explore the effects of working posture, tool use and force level on physiological stress. We expect the derive results can be applied in cleaning work arrangement and tool selection.
Experiment result shows the participants use a long-handle brush will maintain a significantly higher force on WiiFit surface and time efficiency than that use a sessile brush. But, the sessile brush use caused less muscle strain in subjects’ arms than the long-handle brush use while scrubbing floor and toilet-height surface. Force level and working posture, affected by working surface height and tool use, significantly affect participants’ subjective (VAS) and objective (heart rate) workload and their preference of tool use. Most participants (73.3%) prefer using a long-handle brush for floor cleaning with low-medium force requirement, but 46.6% prefer using a sessile brush for high exertion requirement. When the cleaning force demand increased or the surface raised to a toilet-height, most participants (73.3%) switch their preference to a sessile brush use. The logistic regression analysis indicated that VAS was the most significant predictor, followed by surface height, in predicting participants’ preference tool use. Accordingly, we suggest the prescription of tool use should consider the working height, force demand, and even subjective feeling of workload.
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