The temperature of the environment is one of the factors affecting human performance. Heat stress may represent an additional load on the cardiovascular system. Chad and Brown (1995) determined the differences in thermoregulatory responses and the levels of muscle fatigue in the seated worker, performing a task involving a light metabolic load, versus the standing worker, undertaking a lifting task of a heavier metabolic load, in different climatic conditions. The results showed that environmental heat significantly influenced the cardiovascular and thermoregulatory systems in workers performing both light and heavy work tasks. Litchtenbelt et al. (2004) concluded that the averagemetabolic responsewas significantly higher in winter compared to summer. Maiti (2008) conducted a field study related to the building construction to determine working heart rate and effect of environmental conditions on the physiological stress of the female workers and suggested modification of work place and work methods to compensate the health hazard conditions caused by not getting sufficient rest in the field. Fredericks et al. (2008) measured oxygen uptake, heart rate, blood pressure and rating of perceived exertion in a study of a metal pouring operation in small foundry. Maiti and Bagchi (2006) examined the effect of lifting parameters and their interactions on heart rate and concluded that the interaction effects between different lifting parameters should be considered

Table 1. Demographic details of the subjects.