An ergonomics approach to refrigerator design for the elderly person.

The objective was to determine a set of refrigerator design guidelines for independent living elderly women. The study was conducted with a refrigerator mockup with interchangeable internal features. Twelve elderly women participated, both in a standing and seated (wheelchair) position. The participants were videotaped as they simulated use of shelves and drawer, and they rated these components and their positions for acceptability of reach, visibility of contents, and personal preference. Participants then used a variety of mockup items to configure the refrigerator to their own preferred design. These were then analysed and synthesised into three 'consensus' designs combining the features of most of the others.

An evaluation of a weightlifting belt and back injury prevention training class for airline baggage handlers.

This study evaluated the efficacy of a commercially available weightlifting belt in relation to reduction of lumbar injury incident rate and severity of injuries over an 8-month period. The study used 642 baggage handlers working for a major airline company as participants. Four treatment groups were randomly selected: a group receiving the belt only, a group receiving a 1 h training class only, a group receiving both a belt and a 1 h training class, and a control group receiving nothing. Two treatment groups were added which contained participants who discontinued use of the belt prior to the end of an 8-month study period. Results indicated that there were no significant differences for total lumbar injury incident rate, restricted workday case injury incident rate, lost workdays and restricted workdays rate, and worker's compensation rates. There was, however, a marginal significant difference for lost workday case injury incident rate. Groups with participants who wore the belt for a while then discontinued its use had a higher lost day case injury incident rate than did either the group receiving training only or the control group. Compliance was an overriding factor as the belt questionnaire response indicated that 58% of participants in the belt groups discontinued use of the belt before the end of 8 months. Comments made on the survey forms indicated that the belt was too hot. Similarly, comments suggested that the belt rubbed, pinched, and bruised ribs. Based on these results, the weightlifting belt used for this study cannot be recommended for use in aid of lifting during daily work activities of baggage handlers. Results indicate that use of the belts may, in fact, increase the risk of injury when not wearing a belt following a period of wearing a belt. As industries are experimenting with the use of belts, it is recommended that great care be taken in any further evaluation and close attention directed towards injuries which occur when not wearing the belt following a period of wearing the belt (ie, off-the-job injuries).

Factors affecting minimum push and pull forces of manual carts.

The minimum forces needed to manually push or pull a 4-wheel cart of differing weights with similar wheel sizes from a stationary state were measured on four floor materials under different conditions of wheel width, diameter, and orientation. Cart load was increased from 0 to 181.4 kg in increments of 36.3 kg. The floor materials were smooth concrete, tile, asphalt, and industrial carpet. Two wheel widths were tested: 25 and 38 mm. Wheel diameters were 51, 102, and 153 mm. Wheel orientation was tested at four levels: F0R0 (all four wheels aligned in the forward direction), F0R90 (the two front wheels, the wheels furthest from the cart handle, aligned in the forward direction and the two rear wheels, the wheels closest to the cart handle, aligned at 90 degrees to the forward direction), F90R0 (the two front wheels aligned at 90 degrees to the forward direction and the two rear wheels aligned in the forward direction), and F90R90 (all four wheels aligned at 90 degrees to the forward direction). Wheel width did not have a significant effect on the minimum push/pull forces. The minimum push/pull forces were linearly proportional to cart weight, and inversely proportional to wheel diameter. The coefficients of rolling friction were estimated as 2.2, 2.4, 3.3, and 4.5 mm for hard rubber wheels rolling on smooth concrete, tile, asphalt, and industrial carpet floors, respectively. The effect of wheel orientation was not consistent over the tested conditions, but, in general, the smallest minimum push/pull forces were measured with all four wheels aligned in the forward direction, whereas the largest minimum push/pull forces were measured when all four wheels were aligned at 90 degrees to the forward direction. There was no significant difference between the push and pull forces when all four wheels were aligned in the forward direction.

The influence of supporting the Oxylog instrument on estimated maximal aerobic capacity during a step test and heart rate in a lifting test.

This study investigated the influence of wearing, an Oxylog mask and heart rate monitor while the Oxylog instrument was supported in a stand versus that of wearing the Oxylog mask, heart rate monitor, and the Oxylog instrument, on oxygen consumption (VO2) and heart rate response during a graduated submaximal step test protocol. Also, the predicted maximal aerobic capacities ( VO2max) produced by the two graduated step tests were compared. In addition, differences in the working heart rates in a submaximal lifting test were analyzed in two lifting tests, one with the participant wearing the Oxylog mask, heart rate monitor, and Oxylog instrument and the other required the participant to only wear a heart monitor. Seventeen experienced male manual materials handlers participated in the study, and each treatment was seen by each participant in a randomized Latin Square design. Results from the two investigations indicate that there was no significant difference in the estimated maximal oxygen consumption (p = 0.1384) and no significant difference in the heart rate between the two lift tests. The analysis did show that the 4th stage (participants reaching their physiological limits) of the step tests indicated a statistically significant difference (p = 0.0259 for oxygen consumption, and p = 0.0465 for heart rate).

Age and weight effects on motor nerve conduction time measurements in an asymptomatic industrial population.

Motor conduction delay has been demonstrated in patients with carpal tunnel syndrome (CTS), however, there is also evidence that conduction slowing can be effected by other factors, e.g., the aging process. Recent development of the digital electroneurometer, a hand-held, battery-powered device for measuring motor nerve conduction time, has made this test available for CTS screening in industry. A cross-sectional study of 77 industrial workers was performed to determine the relationship between median motor nerve conduction time at the carpal tunnel and select personal factors. Motor nerve conduction time increased with age, length of employment, and weight. However, these variables accounted for only 20.3% of the variance in conduction time. The study indicates users of this device should be aware of these effects, and that other sources of variation must be identified and controlled if motor nerve conduction tests are to be used for CTS screening in industry.

Microwave emissions from police radar.

This study evaluated police officers' exposures to microwaves emitted by traffic radar units. Exposure measurements were taken at approximated ocular and testicular levels of officers seated in patrol vehicles. Comparisons were made of the radar manufacturers' published maximum power density specifications and actual measured power densities taken at the antenna faces of those units. Four speed-enforcement agencies and one transportation research institute provided 54 radar units for evaluation; 17 different models, encompassing 4 frequency bands and 3 antenna configurations, were included. Four of the 986 measurements taken exceeded the 5 mW/cm2 limit accepted by the International Radiation Protection Association and the National Council on Radiation Protection and Measurement, though none exceeded the American Conference of Governmental Industrial Hygienists, American National Standards Institute, Institute of Electrical and Electronic Engineers, or Occupational Safety and Health Administration standard of 10 mW/cm2. The four high measurements were maximum power density readings taken directly in front of the radar. Of the 812 measurements taken at the officers' seated ocular and testicular positions, none exceeded 0.04 mW/cm2; the highest of these (0.034 mW/cm2) was less than 1% of the most conservative current safety standards. High exposures in the limited region directly in front of the radar aperture are easily avoided with proper training. Results of this study indicate that police officer exposure to microwave radiation is apparently minimal. However, because of uncertainty in the medical and scientific communities concerning nonionizing radiation, it is recommended that law enforcement agencies implement a policy of prudent avoidance, including purchasing units with the lowest published maximum power densities, purchasing dash/rear deck-mounted units with antennae mounted outside the patrol vehicle, and training police officers to use the "stand-by" mode when not actually using radar.

The effects of biofeedback on carpal tunnel syndrome.

Behaviour modification based on audible electromyographic (EMG) biofeedback signals was used to discourage the awkward hand postures and the exertion of excessive force with the fingers, which are suspected of causing carpal tunnel syndrome (CTS). The null hypothesis was that participation in such a biofeedback programme has no effect on CTS symptoms. Before and during an 8-week study, data were collected from two groups of five female assembly line workers each. The biofeedback group received training and input, while the control group did not. Test results indicated that the null hypothesis could not be rejected.

Vibrometry testing for carpal tunnel syndrome: a longitudinal study of daily variations.

The method of limits procedure was used to obtain 84 120Hz vibration thresholds, over a 3-month period, on four age-matched women with different levels of carpal tunnel syndrome (CTS). Each woman used a keyboard for 4 hours a day during work. Testing was conducted in a room with a temperature of 28 degrees C +/- 2 degrees C after 20 minutes acclimation. Results indicate vibration thresholds vary significantly from day to day and also demonstrate how a single vibrometry measure may falsely identify the participant's true CTS condition. Specifically, a single measure could account for a negative CTS determinations in affected wrists or positive CTS determinations in healthy wrists. Subsequent analysis revealed menses related fluid retention and day of the week increase the vibration thresholds. Analyzing the levels of fluid retention by day of the week indicates a compounding effect of the personal and occupational risk factors.

Correlation of injury occurrence data with estimated maximal aerobic capacity and body composition in a high-frequency manual materials handling task.

This article evaluates the correlation between injury occurrence, step test estimated maximal aerobic capacity (VO2max), and body composition in a high-frequency manual materials handling task. The study used 212 highly trained male manual material handlers working for a major materials handling company. Three locations across the United States (western, midwestern, and southeastern) were chosen based on similarity of size and function. An estimated maximal aerobic capacity was obtained for each participant using a submaximal bench step protocol. Also, a percentage body fat estimation was randomly obtained for approximately 25% of the participants. The correlation between injury occurrences, absolute VO2max, relative VO2max, and percentage body fat were analyzed. Also, the relationship between both VO2max estimations and percentage body fat was analyzed. Finally, the correlation between location VO2max and percentage body fat was studied. Results indicated no significant difference between absolute VO2max, injury, or percentage body fat. Relative VO2max suggested a significant relationship with injury occurrences and body composition. Body composition also indicated a significant correlation with injury occurrences. Finally, location played a significant factor in injury occurrence, step test estimated VO2max, and estimated body composition. This investigation demonstrates significant evidence of the predictability of employee injury occurrence and the fitness estimation methods used. In a high-frequency manual materials handling task, high occurrences of injury were significantly correlated with low estimated relative maximal aerobic capacity and high estimated percentage body fat.

Use of motor nerve conduction testing and vibration sensitivity testing as screening tools for carpal tunnel syndrome in industry.

Increased attention to carpal tunnel syndrome in industry has resulted in the development of several proposed screening tests. This investigation evaluated the use of two portable devices for measuring motor nerve conduction time and tactile sensitivity to 120 Hz vibration in a field setting. Forty-seven control participants, 63 manufacturing plant workers with and without symptoms of carpal tunnel syndrome, and 22 patients with physician-diagnosed carpal tunnel syndrome were tested with the NervePace electroneurometer and the Vibration II vibration threshold measurement device. Nerve conduction time differed significantly between the controls, the asymptomatic workers, and the participants with carpal tunnel syndrome or symptoms of carpal tunnel syndrome. The vibration threshold was higher in the carpal tunnel syndrome group than in the other groups; however, further examination of the data revealed no differences in threshold unless nerve conduction time exceeded the control mean by at least three standard deviations. The false-negative rates associated with the tests limit their usefulness in screening for carpal tunnel syndrome.