Maintenance Operations: Workstation Adjustment, Working Posture, and Workers' Perceptions Nico J. Delleman, 3-46 Isometric Pull and Push Strengths of Paraplegics in the Workspace: 1. Strength Measurement Profiles Biman Das, Nancy L. Black, 47-65 Isometric Pull and Push Strengths of Paraplegics in the Workspace: 2. Statistical Analysis of Spatial Factors Biman Das, Nancy L. Black, 67-80 Method of Testing the Penetration of Acid Solutions Through Safety Gloves Jolanta Liwkowicz, Joanna Kowalska, 81-88 The Indigenous Fisherman Divers of Thailand: Diving Practices David Gold, Soomboon Aiyarak, Somchai Wongcharoenyong, Alan Geater, Wilawan Juengprasert, Wayne A. Gerth, 89-112 Low Back Muscle Activity in an Automobile Seat with a Lumbar Massage System Mike Kolich, Salem M. Taboun, Ali I. Mohamed, 113-128 Working Conditions in Small Private Enterprises in Poland Marta Derlicka, Houshang Shahnavaz, 129-143

Maintenance Operations: Workstation Adjustment, Working Posture, and Workers' Perceptions
Nico J. Delleman

In the study maintenance workers were involved in pneumatic wrenching, oxy-gas cutting, and grinding at 5 different heights. Working posture and workers' perceptions were measured. Guidelines on working height were formulated in order to minimize the load on the musculoskeletal system. Data from the present experiment as well as from literature were studied in depth in order to disclose generic mechanisms behind the adoption of working postures during visual-manual operations in relation to workstation adjustment. It was found, for instance, that the working posture was constrained by a strictly followed relationship between gaze inclination and head inclination for-/backwards. Also, the study provided insight into the role of visual interference, viewing distance, manipulation distance, hand grip of the tool, and body support for stability. Concerning evaluation criteria for working postures, it was concluded that neck flexion/extension (i.e., head inclination for-/backwards versus trunk inclination for-/backwards) seems to be the dominant determinant of neck load, as compared to head inclination for-/backwards. Furthermore, the position of the upper arm with respect to the trunk, that is, shoulder flexion/retroflexion in particular, seemed to be a dominant determinant of shoulder and shoulder girdle load, as compared to upper arm elevation.

Isometric Pull and Push Strengths of Paraplegics in the Workspace: 1. Strength Measurement Profiles
Biman Das, Nancy L. Black

The isometric strength profiles of male and female paraplegics were determined for pull and push strengths in the normal, maximum, and extreme working reach envelopes. A computerized isometric strength measurement system was designed and constructed for the purpose. The strongest pull location was at extreme reach vertically above the shoulder and the strength values for males and females were 473 and 318 newtons (N), respectively. The strongest push location was at maximum reach, at vertical (f) angle of 45° and at horizontal (q) angle of 45° for males and at 0° for women and the strength values were 235 and 172 N, respectively. The nature of the strength profiles was found to be similar for both the sexes. The pull and push strengths of the female were 77 and 68% that of the male, respectively.

Isometric Pull and Push Strengths of Paraplegics in the Workspace: 2. Statistical Analysis of Spatial Factors
Biman Das, Nancy L. Black

The effect of reach levels, horizontal angles, and vertical angles on isometric pull and push strengths of male and female was determined. Highly significant increases in men's push strength were found between extreme to maximum reaches, and from extreme to normal reaches. However, for women's push strength, a significant increase was found only between extreme to maximum reach. Significant or highly significant increases were found in men's and women's pull strength between the horizontal angle (q) sagittal through the active shoulder (90°) and other angles (0, 45, and 135°). However, for men's push strength, highly significant increases were found between the horizontal angle 45° from the frontal plane, and other angles. For women's push strength, significant or highly significant increases were found between the horizontal angles 0° and angles of 90 and 135° . For men's and women's pull strength, significant or highly significant increases were found between the vertical angle (f), 90° , and other angles (-20, 0, and 45°). Similar increases were found for women's push strength between the 45° angle and other angles. In the design of a workstation for paraplegics that requires pull and push forces, consideration must be given to the spatial factors.

Method of Testing the Penetration of Acid Solutions Through Safety Gloves
Jolanta Liwkowicz, Joanna Kowalska

Because they cause burns that are difficult to heal, acids are dangerous, and steps should be taken to ensure that the human skin does not come into contact with them. For this purpose safety gloves are generally used by workers who have to handle acids. Such gloves need to be tested to ensure that they are acid resistant. Standard EN 374 (European Committee for Standardization [CEN], 1993c) specifies a method of testing the permeation of liquid chemicals, on a molecular level, through glove material, but it may be difficult to ensure the fitness of the joints of a two-compartment cell, when gloves are lined with jersey. To deal with this a simple pH-meter method to test the permeation of acid and alkali solutions through safety gloves has been developed. The permeation of H₂SO₄, HCl, HNO₃, and CH₃COOH through gloves made from neoprene, nitrile, and PVC was tested. This method seems to be simple and economical.

The Indigenous Fisherman Divers of Thailand: Diving Practices
David Gold, Soomboon Aiyarak, Somchai Wongcharoenyong, Alan Geater, Wilawan Juengprasert, Wayne A. Gerth

Diving practices of a group of indigenous people living on Thailand's west coast were investigated. Village chiefs were first interviewed using a questionnaire. Three hundred and forty-two active divers were then interviewed by health care workers using a second questionnaire. Field observation was used to further develop information and confirm diving practices. Divers in 6 villages, whose basic means of making a living is from diving for marine products such as fish and shellfish, have diving patterns that put them at substantial risk of decompression illness. Breathing air from a primitive compressor through approximately 100 m of air hose, these divers have long bottom times coupled with short surface intervals. Forty-six point two percent of the divers indicated that they would not make a stop during ascent from a long deep dive (40 m for 30 min). When comparing their previous day of diving to the U.S. Navy Standard Air Decompression Table (U.S. Navy, 1993), 72.1% exceeded the no-decompression limits set by the tables. Diving patterns point to a need for more in-depth research into the diving patterns of this indigenous group. Future research should include the use of dive logging devices to record depths and times. There is also a need to provide divers with information and training to reinforce positive practices and strengthen knowledge of the risks associated with their current diving practices.

Low Back Muscle Activity in an Automobile Seat with a Lumbar Massage System
Mike Kolich, Salem M. Taboun, Ali I. Mohamed

This investigation was conducted to determine the effects of a massaging lumbar support system on low back muscle activity. The apparatus included a luxury-level automobile seat, six 10-mm diameter bipolar surface electrodes, an amplifier, an analog-to-digital conversion board, data acquisition software, and a personal computer. Six experimental conditions, each involving a variation of massage time, were considered. The dependent variable was the change in the root mean square variation of the EMG signal. One minute of lumbar massage every 5 min was found to have a beneficial effect on low back muscle activity (as compared to no massage). This may prove to be an extremely important result in the quest to combat low back pain attributable to automobile seating.

Working Conditions in Small Private Enterprises in Poland
Marta Derlicka, Houshang Shahnavaz

The study deals with working conditions in small private enterprises in Poland. Data come from 50 small enterprises from the Warsaw area. Information about the evaluation of working conditions and the existence of programmes for their improvement was gathered with the help of questionnaires addressed to employees and employers. The results constitute a "photograph" of the Polish reality at the beginning of its transition from planned to market economy. The study revealed a lack of programmes for the improvement of working conditions in a significant number of the enterprises studied as well as little interest in occupational safety on the part of employers (owners). The study also revealed that all decisions-including those about the improvement of working conditions-were made by employers. Hence, the need for the widest possible dissemination of knowledge on occupational safety and the protection of human in the working environment with particular stress put on employers. Employers who are knowledgeable in this field and who are aware of its importance can significantly influence the improvement of working conditions in small enterprises.