Thermoregulation and thermal comfort of prepubertal children during exercise in cold, neutral and warm environments

Thermoregulation is an essential homeostatic system which maintains a body core temperature of ~37℃ which is necessary for optimal cellular function. This system is continually challenged by daily activities and a constantly changing environment. These disruptions can have an impact on thermal comfort, and in extreme cases on general wellbeing and health. The current literature on children’s thermoregulation is limited, focused primarily on the physiological responses and mostly, in the heat. Children’s thermal perception of different environments during exercise is still a largely unexplored area. Therefore, the focus of this PhD thesis was to significantly extend the knowledge of prepubertal children’s thermoregulatory responses and thermal comfort during exercise in a cold, neutral and warm environment. Chapter 1 of the thesis critically appraises the current literature on specific characteristics of paediatric thermoregulation in cold, neutral, and warm environments. From there, the project was sub-divided into three main research blocks, each with specific aims and methodologies: thermoregulation during exercise in a cold environment (Chapter 2), in a neutral environment (Chapter 3), and in a warm environment (Chapter 4).

The overall findings from the studies conducted in a cold environment (studies 1 & 2) were (1) no correlation was found between thermal sensation scores and skin temperatures, therefore pre-pubertal children’s thermal comfort limits were determined by their thermal perception data and, (2) adult-based models can be used to predict children’s thermal comfort if they fit the targeted climate and activities (i.e. indoor/outdoor, cold/neutral ambient temperatures, active/passive). The main outcomes from work in a neutral environment (study 3) were (1) prepubertal children had the highest skin temperatures, followed by pubertal children and adults, (2) prepubertal and pubertal girls and boys had similar skin temperatures and distributions unlike adults, where men and women showed different absolute temperatures and distributions and, (3) these age and sex differences may be due to the use of different heat loss pathways, and due to differences in body anthropometry (i.e. body fat/muscle percentages). The findings from the study conducted in warmer environments (study 4) were (1) children do show different sweat rates across different regions of the body, (2) children show a different sweat distribution compared to adults, (3) they also have a lower sweat output compared to adults in similar conditions, not meeting their required evaporative heat loss to achieve heat balance and (4) prepubertal boys had higher absolute sweat rates and a different distribution compared to the prepubertal girls.

To summarise this thesis, children indeed thermoregulate differently to adults, showing for the first-time differences in physiological responses of skin temperature and sweat production via body mapping approaches, and perceptual responses relating to thermal comfort. This information can already be useful for companies to improve the design and promotion of their clothing for children, as well as aid in improving the accuracy of current models to target them specifically for children.