Showing papers by "Barbara Griefahn published in 1997"

Acclimation to three different hot climates with equivalent wet bulb globe temperatures.

Abstract: The present study examined 2 hypotheses: Irrespective of the actual composition of thermal factors, the course of acclimation is similar in hot climates which are equivalent in terms of the WBGT. Acclimation to a defined hot thermal environment confers equal acclimation to any other equivalent climate. These hypotheses were supported with 3 substantially different but equivalent climates with WBGTs between 33.4 and 33.6 degrees C. Eight subjects (6 male, 2 female, 19-32 yrs) executed a treadmill walk (4 x 25 min, 4 km/h, 0 degree) while exposed to either a warm-humid, a hot-dry or a radiant heat condition on 15 consecutive days. On the following 2 days, those adapted to the warm-humid or to the radiant heat condition were exposed to the hot-dry climate and those adapted to the latter were exposed to the warm-humid climate. During the experiments, rectal temperatures, skin temperatures at three sites (forehead, chest, leg) and heart rates were measured continuously. Sweat loss was determined by weighing the subjects before and after the daily trials and during the breaks. At the same time, the subjects rated their actual well-being. Disregarding minor differences during the courses of acclimation, both hypotheses were verified.

Working in Moderate Cold: A Possible Risk to Health

Abstract: Working in Moderate Cold: A Possible Risk to Health: Barbara GRIEFAHN, et al. Institute for Occupational Physiology, University of Dortmund—Many worktasks in the food industry are carried out in moderately cold climates (-5 to 15°C), a situation which is assumed to contribute to the genesis and manifestation of several chronic diseases. The present report concerns a cross-sectional study, in which 1, 213 workers in cold environments, mainly from distributors, meat productions, and from breweries completed an extended questionnaire where personal variables and a large spectrum of working conditions, of acute and chronic symptoms, complaints and diseases were ascertained. High prevalences were found for non-specific symptoms, gastrointestinal complaints, pains in the back and in the joints, rheumatic and bronchitic complaints, colds, hearing problems, and the symptoms of the white finger disease. Some of them were significantly associated with the climate at the workplace, particularly with cold, changes in temperature, and drafts. The results support the hypothesis that moderate cold at the workplace constitutes a health risk and form the basis for further, more directed analytical studies. (J Occup Health 1997; 39: 36-44)

Visual contrast thresholds during single-axis and dual-axis whole-body vibrations (5 hz, 1.2 ms-2)

Abstract: The hypothesis was proved that whole body vibrations transmitted through the seat impair spatial retinal resolution and oculomotor alignment parallel to the vibration axis. More specifically, it was assumed that the decrement increases gradually from single-axis lateral via single-axis vertical and dual-axis linear to dual-axis circular motions. 20 subjects (19-26 yrs, 14 men, 6 women) with good vision participated in the study where in separate experimental sessions either fixation disparity or contrast threshold for vertically and horizontally oriented test patterns were determined during 5 conditions. The latter comprized a control (az = aY= O) and 4 conditions where 5 Hz sinusoidal vibrations of 1.2 ins-2 r.m.s. were applied separately, either in the vertical or in the lateral direction or simultaneously in both directions, once without and once with a phase shift of 90° thus causing dualaxis linear or circular motions. The variability of vertical fixation disparity and contrast thresholds for horizontal gratings increased significantly whenever the subjects were exposed to vertical motions (alone or combined with lateral motions). These results indicate an increased difficulty to recognize properly characters and graphic patterns that contain horizontal lines. This may lead to the development of asthenopic complaints.

Fifth international congress on sound and vibration

Abstract: Sixteen female and fifteen male subjects, 19-51 years of age participated in the present study. Its purpose was to determine various combinations of sinusoidal simultaneously presented (dual-axis) vertical and lateral whole-body vibrations that are sensed as equally strong as a preceding single-axis reference (aW= 1.25 ins-2 r.m.s.) which was applied in either of both directions only and which had the same frequency, namely 1.6, 3.15,6.3 or 12.5 Hz. The test motion consisted of a constant predefine and a variable component. The first was applied in the same direction and with either of 5 predefine percentages of the acceleration of the reference (10, 25, 50, 75, 90 ‘ZO). The variable component was perpendicularly oriented to the first (resp. to the reference); its magnitude was varied by the subjects until the dual-axis test signal was judged as equally strong as the single-axis reference. The curves of equally sensed combinations determined for the 4 frequencies were bended right-downwards as expected due to ISO/DIS 2631. But there were remarkable quantitative discrepancies for frequencies above 1.6 Hz with an underestimation of lateral vibrations; the factor kYbeing 1.5- 1.9 greater than in the standard. It is concluded that the weighting factors for lateral vibrations above 1.6 Hz need to be corrected for the proper evaluation of discomfort caused by multi-axis whole-body vibrations.