Physiological strain of wearing aluminized protective clothing at rest in young, middle-aged, and older men

Abstract

During surveillance tasks in hot industrial working sites it is often necessary to use reflective protective clothing against radiant heat sources. The aim of the present study was to assess the thermal strain of wearing radiation protective clothing in men of differing age. The study subjects were 24 healthy, normotensive, unacclimated men: 9 young (20–28yr) (group I), 9 middle-aged (43–52yr) (group II) and 6 older men (58–65yr) (group III). The subjects were similar in daily physical activity (low), body size and subcutaneous fat thickness. All subjects rested in a sitting position for 60min in a climatic chamber in two experiments with WBGT of around 29°C that represented a low stress (LS, low radiant heat and little clothing) and high stress (HS, high radiant heat and aluminized protective clothing). In LS, the subjects wore shorts and the WBGT was driven by air temperature and humidity (tnwb =25°C, tg =38°C). In HS, subjects wore an aluminized suit and the WBGT was driven by high radiant heat from infrared heaters (tnwb =22°C, tg=41°C). During the experiments, rectal and skin temperatures, heart rate, body mass loss, and blood pressure were measured, and subjective ratings were collected. No differences in rectal temperature, skin temperatures and in total body sweat rate were observed between the age groups in LS and HS. Heart rate response was not different between LS and HS, but it was significantly higher in group III compared to groups I and II at rest and at the end of both exposures. Mean arterial blood pressure was significantly higher in groups III and II than in group I (p<0.01) in both experiments. Significantly lower subjective ratings of thirst (p<0.05) were found in the oldest group than in groups I and II in LS and HS. In HS all subjective ratings pointed towards a greater heat strain than in LS. There was a greater sweat secretion (p<0.05) in HS than in LS in groups I and III. In conclusion, present heat stress conditions did not cause marked heat strain, which seemed to be within acceptable limits for all age groups. Healthy older men were able to tolerate the heat stress tests as well as young and middle-aged men. However, lower ratings of thirst in the oldest group may indicate a greater risk for dehydration.Relevance to industryResults of the present study suggest that during relatively short resting exposures to heat without and with radiation protective clothing (WBGT around 29°C) older men seem not to be at a greater risk for excessive heat strain than young and middle-aged men. However, in a hot environment dehydration is a potential risk factor for older workers. Thus, special attention should be paid to the importance of fluid replacement in older persons at hot workplaces, for example, by giving information and providing adequate amounts and easy availability of fluids.