Report on Ergonomic Issues - Case Study Example

The ergonomic issues involved The ergonomic issues involved are the musculoskeletal disorders of the hands, arms shoulder, and back of rangers from riding snowmobiles up to 10 hrs. This musculoskeletal disorder is caused by the pressure on the joints and vibrations experienced by the body when riding a snowmobile. A factor which increases vibrations experienced by rangers is because of the roads traveled when patrolling around the park. The roads used by rangers, especially from the west entrance to old faithful, had become washboard roads caused by the large volume of travelers in these areas. 2. The research conducted (and what type of study) An ergonomic study was conducted by National Institute for Occupational Safety and Health (NIOSH) on the rangers of Yellow Stone Park. Several tests were used such as the Rhythmic Test, Tremor Test, and the Vibroactile Test, to determine the reason why the rangers are experiencing musculoskeletal disorders and to find a way to prevent this kind of disorder. The first test used was the Rhythmic test. This test is used to determine the reaction time and coordination on the right and left hands. The rhythmic tests required the participants to tap a circular pad (4–inch diameter) in time with a steady metronome beat (1.0 Hertz [Hz] slow test, 2.5 Hz fast test), either alternating palm side of hand to back of hand (supination/pronation) or tapping with the index finger. At the end of the test administration a numerical coordination index is calculated, which can be compared to the normal coordination index (CI) range provided with the test battery documentation (NIOSH Health Hazard Evaluation Report, Yellow Stone Park, 2001). With this data, the reaction time and hand coordination of the rangers can be easily compared to the normal reaction time index. The difference will determine the effect of the vibrations experienced while riding a snowmobile on hand coordination. The second test used was the Tremor Test. This test used the Tremor 3.0 software for data analysis. The data collected were: (1) Tremor intensity, often called amplitude or vibration power, calculated as the root–mean–square (RMS), measured in meters per second per second (m/s2) of acceleration in the 0.9 to 15 Hz band during the 8–second test; (2) Center frequency, which is the average frequency of acceleration in the test band, so that 50% of the energy that drives the tremor is produced at frequencies above the center frequency and 50% is produced below; (3) Tremor Index, calculated for each hand from five parameters (e.g., tremor intensity, center frequency, standard deviation of the center frequency, harmonic index, and standard deviation of the harmonic index.); and (4) Combined index for both hands (NIOSH Health Hazard Evaluation Report, Yellow Stone Park, 2001). This test measures the vibrations experienced by the rangers in riding the snowmobiles and the intensity of the vibration that will likely cause the musculoskeletal disorder. The third test used is the Vibroactile Sensitivity test. This test was selected to determine the effect of the hand–arm vibration produced by snowmobiles on vibration perception thresholds. The test device used was the Bruel & Kj?r Model 96–27 Vibrometry System. This fully automated system produces a mechanical stimulus (sinusoidal vibration) at a chosen frequency to the pulp of a finger tip; the participant indicates perception of the vibration by means of a hand–held button similar to that used in a hearing test. The software was configured to test vibration at four frequencies: 31.5 Hz, 125 Hz, 250 Hz, and 500 Hz. Participants placed their right arm on an ascending armrest with the palm lying open on a circular pad, allowing the fingers to hang freely above the vibrating post. The test finger was then placed on the vibrating post with the finger slightly curved and resting lightly on the post. Participants controlled the intensity of vibration with the hand–held button, tracking back and forth between levels of stimulus perception and non–perception (NIOSH Health Hazard Evaluation Report, Yellow Stone Park, 2001). The data gathered in this test will determine the effect of the vibrations experienced by the hand-arm to the perception of the ranger. 3. The findings and recommendations The finding The average tremor indices for the right hand (99.5–95.4), the left hand (96.2–90.4), and the combined index for both hands (97.8–92.9) all decreased from the a.m. to the p.m. tests and were less than a normal score of 100, but the decreases were not statistically significant. The lower the score on the tremor index test, the poorer the performance on this test. One of the tremor measurement components (center frequency–right hand) showed a statistically significant change from a morning value of 7.4 Hz to an afternoon value of 6.5 Hz (p=0.003), likely contributing to the index decreases from a.m. to p.m., but this measurement has no particular relevance when considered by itself. Nonetheless, it is noteworthy that the right hand activates the thumb–controlled throttle on the snowmobile. No vibrotactile measurements showed a significant change, and only one coordination measurement (pronation/supination–right hand) showed a significant change (p=0.04). The pronation/supination frequency score increased from 3.8 to 4.9, which is an indication of better performance, likely due to a learning effect. There was no similar learning effect for the left hand. The right hand index score and the combined mean tremor index score for the 17 Park Service employees used in this analysis were, respectively, 100.4 (range: 61–158) and 98.6 (range: 69–133). The majority of the test scores were close to the normal mean of 100 and within the range of one standard deviation (SD) of 20 (NIOSH Health Hazard Evaluation Report, Yellow Stone Park, 2001). The results of the vibrotactile sensitivity tests, the coordination tests, and the tremor tests were not conclusive, but were consistent with the symptoms reported by the YNP personnel. The test results suggest that snowmobile use, particularly depressing the throttle control with the thumb, fatigues the muscles of the hands and arms. The main reason why rangers experience musculoskeletal disorders is because of the adjustment issues they have with the respective snowmobiles they use. This adjustment problems such as suspensions and the handlebar reach causes awkward postures which cause the muscle pains experienced by the rangers. Therefore, the park should provide customized snowmobiles to each ranger, which should perfectly adjust for their comfort and to lessen the vibrations experienced. The park could also consult with snowmobile manufacturers about the design flaws of their machines which causes musculoskeletal disorders. Another solution for the park is to fix the heavily used roads which cause additional vibrations, train their rangers on the proper handling of snow mobiles and to limit the use of these machines. 4. Any other significant point. A significant point to think about in this case is the fact that only Yellow Stone Park rangers are experiencing this kind of disorder comparing it to other parks or to people who frequently use snowmobiles. The only logical answer for this question is that Yellow Stone Rangers are not well trained in handling snowmobiles, thus, the reason for their disorders. The park should, before the start of every winter season, train their rangers in handling these machines to lessen the health related problems they are experiencing. The park should, if snowmobiles are causing this much problems to the rangers, find another alternative means for rangers to patrol around the park during winter. In the long span of time of the park having this kind of problem it did not bother looking for alternative transportation for the rangers. References: NIOSH Health Hazard Evaluation Report, Yellow Stone Park, (2001). Retrieved July 13, 2011 from http://www.cdc.gov/niosh/hhe/reports/pdfs/1999-0283-2855.pdf Off-road Vehicles, Air Quality, and Human Health, (n.d.). Retrieved July 14, 2011 from http://www.prtvt.org/orv-emissions.htm Peterson, J. (2009). Why You Must Ditch The Snowmobile. Retrieved July 14, 2011 from http://planetgreen.discovery.com/travel-outdoors/good-reason-ditch-snowmobile.html Tostrup, B. (1994). Retrieved July 14, 2011 from http://www.ncbi.nlm.nih.gov/pubmed/7710592 Read More