Gender and age effects on metabolic rates of office work, housework, and different walking speeds

Metabolic rate is an essential factor in determining human thermal comfort. Existing metabolic rates for common activities in the current standards are based on mean adult values and do not include values for the middle-aged and the elderly. This study examines the metabolic rate of 151 Chinese male and female subjects aged 20 similar to 69 during eighteen activities (reclining, 7 types of office work including seated and standing, 5 types of housework, and 5 walking speeds) using an indirect calorimeter in lab studies. The results show that women exhibited lower metabolic heat production rates (6-9% for sedentary and standing activities, 9-13% for household activities, and 4-9% for walking activities) than men across all activities, regardless of age. No age-related declines in metabolic heat production during lower activities (reclining, sedentary, standing, and household). Rather, metabolic heat production rates increased at a rate of 5-7 W/m(2) per decade with age, which is contrary to popular beliefs. Women demonstrated a distinct pattern of changes compared to men, with significant declines observed in sitting and standing activities, at a rate of 2-3 W/m(2) per decade. The ISO and ASHRAE standards tended to overestimate the metabolic rate for standing position activities and significantly underestimate the metabolic rate during walking. Some simple household activities, such as folding cloth, wiping windows, and vacuuming, had a moderate metabolic rate level, significantly higher than standing quiet. These findings could inform the development of interventions to promote healthy ageing and the design of more effective strategies for managing thermal comfort in different populations. It is suggested that the metabolic rate reference table or prediction method in international standards needs modification when applied to the Chinese population.