Acclimatization to Severe Dry Heat by Brief Exposures to Humid Heat

Abstract

Maximal static strengths were determined for one-handed exertions in all directions in the fore and aft plane. Data from 12 males and 10 females (mean age 30·7 yrs, standard deviation (SD)=8·9 yrs, n=22) were obtained with handle heights of 1·0 and 1·75 m. Twelve of the subjects also performed two-handed exertions at the same handle heights. The ratio of mean strengths of females to that of males ranged from 0·50 to 0·83 (for absolute forces) and from 0·63 to 1·00 for forces normalized to body weight. The ratios of one-handed to two-handed strengths ranged from 0·64 to 1·04. Two-handed strengths commonly exceeded one-handed strengths at the lower handle height, but showed fewer significant strength differences (p<0·05) according to direction at l·75m. Both female/male and one-handed/two-handed strength ratios were found to be dependent on direction of exertion and handle height. The observed strength dependencies upon number of hands (one or two-handed), direction of exertion, handle height and sex are discussed. The strength data have implications for use in biomechanical models and task analysis.     

Ratings of acceptable load and maximal isometric lifting strengths: the effects of repetition

The effects of repetition on psychophysically acceptable loads and maximal isometric lifting strengths were studied in two groups of subjects. In both groups, subjects selected acceptable loads for dynamic lifting between table and floor and were tested for maximal and acceptable lifting strength isometrically at knee and waist levels.

In series I, 33 subjects (15 males, 18 females) were tested 4 times with a minimal interval of 5 days between tests. In series II, 12 subjects (8 males, 4 females) were tested daily from Monday to Friday on 2 consecutive weeks.

Differences in acceptable isometric lifting strength between the two groups appeared to arise from minor differences in the instructions given; but in neither series was there a significant change in acceptable lifting strength, either dynamic or isometric. In series I, no change was noted in maximal isometric lifting strength. But in series II there was a gain in maximal lifting strength at knee level of 25%. Also in series II, the acceptable isometric lifting strength at waist level was consistently found to be 60% of the acceptable dynamic lifting strength.     

Circadian Rhythms of Food Intake and Oral Temperature in ‘Morning’ and ‘ Evening’ Groups of Individuals

The most marked ‘ morning ’ and ‘evening ’ types in a psychology class were identified by means of a questionnaire, and asked to record their oral temperatures and food intakes throughout the day during a 4-week and a 4-day period respectively. The morning group had its mean circadian temperature maximum 5 h earlier than the evening group, and had its cumulative food intake distribution curve 1¾ h ahead of the evening group. After adjusting the food distributions by 1¾ h in the time base to get a least-square fit, significant differences between the distributions remained. It is suggested that morning types have a more autonomous 24-hour-periodicity than evening types. It is concluded that the questionnaires have the power to discriminate extreme morning and evening types of individuals in terms of oral temperature and food intake. Food intake seems to be a sensitive enough measure to be included in studies of inter-individual differences of circadian rhythms.