Rodger J. Koppa

The effects of load knowledge on stresses at the lower back during lifting

This study investigated the effects of load uncertainty on the lifting characteristics of 40 male volunteers during the initial portion of a lift. Twenty subjects were experienced weightlifters while another 20 were subjects who had never lifted weights nor held a job that required them to on a regular basis. The subjects each lifted a container 20 × 45 × 40 cm, with handles, from floor to waist height 12 times with loads of 68, 10·2 or 13·6 kg. The loads were lifted under conditions of either havingor not having verbal and visual knowledge of the load magnitude prior to the lift. The subjects were allowed to perform the lift in a manner of their choosing. A 2 (groups) × 3 (loads) × 2 (load knowledge) ANOVA was performed on the data. Maximim force (Fmax) value analysis revealed group and technique differences. The experienced lifters had lower stress levels at L4/L5 and utilized two technique strategies that were dependent upon the load knowledge condition, whereas the non-lifters used the same strategy f...

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.

Low back stress, muscle usage, and the appearance of transient load movement during manual lifting

Abstract Neuromuscular involvement should be considered in biomechanical evaluations of a workers job-related stresses as a potential aid to understanding and reducing the rising incidence of low back problems in industry. Because such interactions have seldom been investigated in multisegmental movements, the present study was undertaken to determine the effects of the involvement of the neuromuscular system during lifting by creating conditions in which subjects had prior knowledge (PK) of a loads magnitude as well as when they had no prior knowledge (NK). Two groups of subjects, experienced and inexperienced lifters ( N =40), lifted loads varying from 6.8 to 13.6 kg under both the PK and NK conditions. Results indicated that two general patterns of load movement were used by the subjects: smooth and oscillatory (irregular transient), with higher peak L4/L5 forces and higher peak trunk movements found in the oscillatory pattern. Significant differences on all stress values were demonstrated by the inexperienced lifters. The inclusion of lift preparation and load knowledge considerations in training programmes and biomechanical models is recommended.

Driver Inputs during Emergency or Extreme Vehicle Maneuvers

Four representative vehicles used in a previous open-loop comparative study were tested with a sampling of volunteers from the general public. The tests included pre-planned and simulated emergency maneuvers. Various vehicle input and response parameters were measured, and the results were used to evaluate current open-loop test maneuvers and parameters. In addition, the degree to which this sampling of drivers utilized the full capabilities of the vehicles was determined. Drivers rarely use the full capabilities of vehicles and tend to adjust their inputs to neutralize differences among vehicles.

STATE OF THE ART IN AUTOMOTIVE ADAPTIVE EQUIPMENT

Although some forms of automotive adaptive equipment designed to enable people who are physically disabled to drive have been on the market for many years, development has been slow until the last 10 to 15 years. Advanced-design, reliable devices have recently become available to allow persons who are severely disabled to gain transportation independence. Equipment for ingress/egress, primary and secondary control, and occupant protection have come on the market or are nearly ready for procurement. Much remains to be done, however, especially in integrating this equipment into a system for transportation. Primary controls (throttle, brake, and steering) and occupant protection still require much research and development. Cost, liability considerations, and a small market demand restrict development, but real progress has been made.

Maximum acceptable weight of lift for an asymmetrical combination manual handling task

Abstract This paper presents a study on a combination lift and lower manual handling task and was designed to simulate the loading of grocery bags into car trunks. Eighteen male subjects performed an externally-paced task of lifting grocery bags loaded with steel shots from 15 cm above the floor and over a wooden sill. There were two different sill heights of 70 cm and 90 cm, and for each of these heights there were three different sill depths of 28 cm, 43 cm, and 57 cm. The dependent variables were the maximum acceptable weight of lift. Constant conditions were temperature (23–26°C), humidity (52–62%), horizontal distance of lift (136 cm), and time of day the subjects performed the lifting. A unique lifting sequence and a modified version of the psychophysical methodology were used to determine the maximum acceptable weight that subjects were willing to lift. There were no significant differences in the weights lifted across the two sill heights but weights lifted over the 28 cm sill depth was significantly more than the weights lifted for either the 43 cm depth or the 57 cm depth.

Torque required from elderly females to operate faucet handles of various shapes.

Contemporary housing design for the elderly features faucet handles of various shapes in the kitchen and bath. Often the elderly users cannot properly grip the faucet handle, whose shape does not allow for sufficient torque to be developed to shut off the water flow. Twenty-three elderly females turned seven different faucet handles in the clockwise and counterclockwise direction, exerting comfortable levels of torque. The only handle that consistently allowed a torque force to be developed superior to that needed to operate working installed water faucets was a medical-type “paddle.” A comparison of the torque needed to terminate water flow in actual water faucets with the torque developed by the standing and seated subjects showed that the nonpaddle handles did not allow subjects to generate sufficient torque to terminate the water flow. The blunt edges of the nonpaddle handles caused substantial hand pain.

Effects of pneumatic screwdrivers and workstations on inexperienced and experienced operator performance

Abstract This study investigated the effects of pneumatic screwdriver characteristics and workpiece orientation on operator productivity. Operators used four pneumatic screwdrivers (two pistol and two straight grip) representing two different clutch types (positive and automatic air shut-off). The two grip types represented both fast (1700 RPM) and slow (1000 RPM) motor speeds. The pneumatic screwdrivers were used at each of three different workstations representing different workpiece orientations (horizontal workpiece at a fixed height, horizontal workpiece with an adjustable height, and angled workpiece with adjustable height). In the first phase of the study, 18 university students (inexperienced operators) participated in a simulated furniture assembly operation. In the second phase, 16 experienced employees of a furniture manufacturing facility participated in an actual furniture assembly operation. The results of the study indicate that operators took longer to complete the required tasks and made more errors when the straight grip screwdrivers were used than when the pistol grip screwdrivers were used. These differences were more pronounced at the end of the task than at the beginning of the task. No strong performance differences were found among the three different workstations used.

Effect of pneumatic screwdrivers and workstations on operator body posture

Abstract Four pneumatic screwdrivers, representing two different motor speeds and grip types, were used by both inexperienced (college student) and experienced male and female operators in a simulated and actual furniture assembly operation, respectively. All screwdrivers were used to set screws in furniture desk tops configured in three different orientations. The workstation/workpiece orientations were chosen to assess both ideal and non-ideal upperarm-forearm, wrist, shoulder and body postures assumed by operators during the assembly task. The results of this study indicate that less deviation of the upperarm-forearm and wrist was assumed by male operators. The female operators, necessarily disadvantaged by strength and stature, assumed postures representing greater body part abduction and deviation from neutral points. No differences were found between inexperienced and experienced operators.

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.