Effects of work and motivation on the heart rates of chronic heat-exposed workers during their regular work shifts

Heart rate is accepted as one of the best indices of physiological strain imposed by physical and environmental stressors. Continuous recordings of ECG were taken in mid-summer and mid-winter from metal workshop workers during their regular 8 hour work shifts at the work area in two plants located in the desert in Israel. Seven workers were studied in Beer Sheva, a semi-arid zone with average daily maximum temperature in the two seasons of 38 and 25°C. Twenty-four worked near the Dead Sea at Sdom, an extreme desert, with corresponding temperatures of 44 and 26°C. The workers in Beer Sheva were motivated to work hard and increase productivity in order to augment their low salaries. No such motivation existed in the plant in Sdom, whose workers were highly paid. Contrary to the expected, the comparison of the heart-rate profiles of the two seasons showed no differences in Sdom while in Beer Sheva, winter heart rates were higher than in summer. In both plants, in both seasons during at least 50% of the work shifts the heart rates were between 80 and 100 beats/min. It is suggested that physical workers tend to regulate their heart rate at the expense of effort and productivity and seems to be independent of work motivation for financial gains. In a few cases when urgent outdoor maintenance tasks were performed by members of a different department in Sdom, heart rates exceeding 150beats/min were recorded for prolonged periods during summer work shifts.