Kazushi Taoda

Measurement of Whole-Body Vibration in Taxi Drivers

Measurement of Whole‐Body Vibration in Taxi Drivers: Mitsuhiko Funakoshi, et al. Kyushu Institute for Social Medicine—In a previous epidemiological study we reported that the prevalence (45.8%) of low‐back pain (LBP) and the two‐year incidence (25.9%) of LBP in 284 male taxi drivers in Japan was comparable with rates reported for other occupational drivers in which LBP frequently occurs. LBP was significantly related with the level of uncomfortable road vibrations, and, importantly, increased with total mileage. The aim of this study was to measure whole‐body vibration (WBV) on the drivers seat pan of 12 taxis operating under actual working conditions. The results were evaluated according to the health guidelines in International Standard ISO 2631‐1:1997. Finally, the relation between total mileage and WBV was investigated. The majority of the frequency‐weighted r.m.s. accelerations of the taxis fell into the “potential health risks” zone, under ISO 2631‐1:1997. It was clear that the taxi drivers were exposed to serious WBV magnitudes. Therefore, occupational health and safety management should be carried out to help prevent adverse health effects in taxi drivers. In particular, reduction of WBV in taxis and shortening of driving time to reduce duration of WBV exposure should be considered. Moreover, because many taxi drivers work 18 h every other day, the shortening of working hours and taking of rest breaks while working should be considered. Frequency‐weighted r.m.s. accelerations of taxis had a tendency to decrease as total mileage increased. The relation between total mileage and WBV should be investigated by taking measurements on the floor and the back rest in addition to the seat pan.

Work schedule differences in sleep problems of nursing home caregivers

Nursing home caregivers (n=775; 604 women; mean age 33.6 years) were studied to examine how work schedules affect their sleep. The shift group (n=536) worked under a rotating two-shift system (n=365), a rotating three-shift system (n=66), or other types of shifts (n=78). The non-shift group included 222 caregivers. Participants completed a questionnaire about working conditions, sleep problems, health, lifestyle, and demographic factors. The two-shift caregivers reported the highest levels of difficulty initiating sleep (DIS, 37.6%), insomnia symptoms (43.0%), and poor quality of sleep (24.9%) among the groups. Adjusted odds ratios for these problems were significantly greater for the two-shift caregivers than for non-shift counterparts: DIS (odds ratio 2.86, 95% confidence interval 1.57-5.20), insomnia symptoms (2.33, 1.36-4.02), and poor sleep quality (2.15, 1.09-4.22). Our data suggest that working under a rotating two-shift system, which has a longer night shift, is associated with an elevated risk of sleep problems for nursing home caregivers.

Application of a new, self-recording, vibratory sensation meter to measure temporary threshold shift of vibratory sensation caused by local vibration exposure

A new, self-recording, vibratory sensation meter measures temporary threshold shifts of vibratory sensation (TTSv) on a finger tip. After exposure to hand-transmitted vibration with exposure frequencies 63 Hz, 200 Hz and 500 Hz, and levels of acceleration 1 g, 2 g, 4 g and 8 g, fingertip measurements were obtained. Temporary threshold shift immediately after the vibratory exposure (TTSVv,0) was estimated for each exposure from the regression analysis by approximation of an exponential function. Time constant (tc) was also estimated at the same time by the analysis. The coefficients of determination were large. Thus, the fit of the exponential function is very good for each exposure. The tc corresponds to the recovering velocity of the temporary shift and implies the half-life period of TTSv. These parameters enable us to examine more generally the relationships of TTSv to the characteristics of exposure vibration, subject and other conditions. On this basis, the estimated TTSv,0 and tc were used to examine the dependency of TTSv on the characteristics of the exposure vibration and the subject. The most effective frequency under the level of 4 g is thought to be between 200 Hz and 500 Hz. TTSv,0 of each subject proportionally increased with power of acceleration. The coefficient of determination on regression analysis was large. This result enables us to estimate TTSv,0 at an arbitrary level of acceleration by use of a regression equation derived from experimental data.

Temporary threshold shift of vibratory sensation induced by a vibrating handle and its gripping force.

Abstract•Objective This study examines the effect of the force with which a vibrating handle is gripped on the temporary threshold shift of vibratory sensation (TTSv) induced by hand-arm vibration. •Methods Six healthy subjects gripped a handle vibrating with a 1/3 octaveband vibration, with a central frequency of 200 Hz and an intensity of 39.2 m/s2. Exposure was for 1 min and 10 min, respectively. Gripping forces for the 1-min exposure were 5 N, 10 N, 40 N and 80 N, respectively, with 0 N push-pull force. Gripping forces for the 10-min exposure were the same as for the 1-min exposure, but omitting 80 N. The vibratory sensation threshold at 125 Hz was measured before and after exposure of an exposed fingertip to vibration. The differences measured determine TTSv,t at timet. TTSv,t determines TTSv,0, that is, the temporary threshold shift of vibratory sensation immediately after exposure to vibration according to the estimate made on the basis of the preceding study. The same experimental conditions were repeated 3 times on different days in a soundproof and thermoregulated room. •Results Our findings show that TTSv increases significantly with increasing gripping force. We also determined the quantitative relationships between TTSv,0 and gripping force as described by the equation % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfKttLearuqr1ngBPrgarmqr1ngBPrgitL% xBI9gBamXvP5wqSXMqHnxAJn0BKvguHDwzZbqegm0B1jxALjhiov2D% aeHbuLwBLnhiov2DGi1BTfMBaebbfv3ySLgzGueE0jxyaibaieYlf9% irVeeu0dXdh9vqqj-hEeeu0xXdbba9frpe0db9Lqpepeea0xd9q8as% 0-LqLs-Jirpepeea0-as0Fb9pgea0lrP0xe9Fve9Fve9qapdbaqaae% GaciGaaiaabeqaamaaeaqbaaGcbaGaeeivaqLaeeivaqLaee4uam1a% aSbaaSqaaiabbAha2bqabaGccqqGSaaldaWgaaWcbaGaeeimaadabe% aakiabg2da9iGbcwgaLjabcIha4jabcchaWjabcIcaOiabbUgaRnaa% BaaaleaacqqGMbGzaeqaaOGaey41aqRaemOrayKaey4kaSIaem4yam% 2aaSbaaSqaaiabdAgaMbqabaGccqGGPaqkcqGGSaalaaa!5B91! {\text{TTS}}_{\text{v}} {\text{,}}_{\text{0}} = \exp ({\text{k}}_{\text{f}} \times F + c_f ),

The temporary threshold shift of vibratory sensation induced by composite-band vibration exposure.

wherekf andcf are constants andF is gripping force. •Conclusion This study revealed the importance of ergonomic design in reducing the force with which a vibrating handle is gripped to prevent an adverse effect of local vibration. The equation devised may help in the quantitative assessment of the effect of reduced gripping force.

A field study of exposure to whole-body vibration due to agricultural machines in a full-time rice farmer over one year

Effect of Nursing Assistance Tools on Preventing Musculoskeletal Pain among Staff in Schools for Disabled Children: Shigeki Muto, et al. Seirei Center for Health Promotion and Preventive Medicine—Objective is to clarify whether nursing assistance tools (a mat with attached handles, a pair of trousers with knee pads and a waist holding belt) prevent musculoskeletal pain, such as low back pain and upper arm pain, and depression, and improve the burden on the lower back and upper arm among staff in schools for disabled children. This study design was a non‐randomized intervention trial. The subjects were 41 staff in two schools for disabled children in Japan. Nursing assistance tools were used with the intervention group to help with their nursing activities. We investigated the one‐month prevalence of low back pain and the degree of burden on the lower back using a questionnaire at the baseline and at the end point 4 to 6 months later. The prevalence of low back pain did not change significantly in either group. In the intervention group, the prevalence of upper arm pain decreased from 47.6% at the baseline to 23.8% at the end point (p=0.063). The percentage of participants with a high level of burden on the lower back from excretory nursing activity decreased from 57.1% at the baseline to 33.3% at the end point (p=0.063) in the intervention group. These results suggest that nursing assistance tools may prevent upper arm pain and improve the burden on the lower back among staff in schools for disabled children; however, these tools did not significantly prevent low back pain and depression.

Exposure to Whole-Body Vibration of Forklift Truck Operators in Dockyards

Eight healthy subjects were exposed to three 1/3 octave-band vibrations (63, 200, and 500 Hz) by hand clasping a vibrated handle in a soundproof and thermoregulated room. The vibratory sensation threshold at 125 Hz was measured before and after the vibration exposure at an exposed fingertip. According to a preceding study, we first determined the relationship between the acceleration of the vibration and the temporary threshold shift of vibratory sensation immediately after the vibratory exposure (TTSv, 0) induced by 1/3 octave-band vibration. We then measured TTSv after the exposure to a composite vibration composed of two 1/3 octave-band vibrations that might induce an equal magnitude of TTSv, 0 on the basis of the above relationship. The TTSv, 0 induced by the composite vibration was not larger than the TTSv, 0 induced by the component vibrations. This result suggests that the component of the vibration inducing the largest TTSv, 0 determines the TTSv, 0 by broad-band random vibration.

Improvement of the Sitting Position of the Computer Operator Using theToes

A field study of exposure to whole‐body vibration due to agricultural machines in a full‐time rice farmer over one year: Hiroji Tsujimura, et al. Division of Occupational and Environmental Health, Department of Social Medicine, Shiga University of Medical Science

Dependency of Temporary Threshold Shift of Vibratory Sensation in Fingertip on 1/3 Octave-Band Hand-Arm Vibration Exposure Period

Low-back disorders are well documented as occupational hazards among forklift truck operators. The potential risk factors that may lead to low-back pain include exposure to whole-body vibration (WBV). In Europe, test methods were developed to evaluate WBV in industrial trucks, and the European Standard which defines the methods has been published. We measured the vibrations of forklift trucks operated in the Hanshin harbour area adopting procedures based on the CEN test and report the evaluation results. If the WBV magnitudes of the ride on forklift trucks in the workplace were less than or comparable to those in the CEN test, the CEN test could be considered useful for the risk assessment of forklift truck operators exposed to WBV. In order to verify the applicability of the CEN test to the evaluation of WBV exposure in the field, we conducted measurements of the WBV of four forklift trucks for 19 d. The trucks had already been examined by the CEN test. The truck velocity, driver position (sitting or not), and gear lever position were also measured, and video footage was obtained for the study. The results indicate that the vertical WBV magnitudes of the four forklift trucks were below the CEN test values. No dominant WBV direction was observed on any of the measurement days. The Health value (obtained by combining the values determined from the vibration in orthogonal coordinates) was comparable to that from the CEN test for one truck. The values for the other three trucks were lower. The data obtained for three forklift trucks were analyzed in each operating condition. The vertical WBV magnitudes and Health values for the three trucks were below the CEN test values when the trucks were travelling forwards with a load. The WBV in the anterior-posterior direction had the largest adverse effect on the human body of the three orthogonal directions when the trucks were used for loading and unloading. The results suggest the CEN test can be applied to the evaluation of exposure to WBV from forklift trucks operating in the vicinity of the Hanshin harbour. It was observed that the anterior-posterior WBV is considerable, mostly through exposure occurring in the lifting mode. However, the CEN test is based on the travelling mode, and further WBV measurements under real working conditions with exact descriptions of detailed work situations and operating conditions are required.