Thermoregulatory responses of prepubertal boys and young men in changing temperature linearly from 28 to 15 degrees C

Thermal Environment of Urban Schoolyards: Current and Future Design with Respect to Children’s Thermal Comfort

Urban outdoor thermal conditions, and its impacts on the health and well-being for the city inhabitants have reached increased attention among biometeorological studies during the last two decades. Children are considered more sensitive and vulnerable to hot ambient conditions compared to adults, and are affected strongly by their thermal environment. One of the urban outdoor environments that children spend almost one third of their school time is the schoolyard. The aims of the present manuscript were to review studies conducted worldwide, in order to present the biophysical characteristics of the typical design of the urban schoolyard. This was done to assess, in terms of bioclimatology, the interactions between the thermal environment and the children’s body, to discuss the adverse effects of thermal environment on children, especially the case of heat stress, and to propose measures that could be applied to improve the thermal environment of schoolyards, focusing on vegetation. Human thermal comfort monitoring tools are mainly developed for adults, thus, further research is needed to adapt them to children. The schemes that are usually followed to design urban schoolyards create conditions that favour the exposure of children to excessive heat, inducing high health risks to them. The literature survey showed that typical urban schoolyard design (i.e., dense surface materials, absence of trees) triggered high surface temperatures (that may exceed 58 °C) and increased absorption of radiative heat load (that may exceed 64 °C in terms of Mean Radiant Temperature) during a clear day with intense solar radiation. Furthermore, vegetation cover has a positive impact on schoolyard’s microclimate, by improving thermal comfort and reducing heat stress perception of children. Design options for urban schoolyards and strategies that can mitigate the adverse effects of heat stress are proposed with focus on vegetation cover that affect positively their thermal environment and improve their aesthetic and functionality.

An energy budget model for estimating the thermal comfort of children

Many children growing up in cities are spending less time outdoors to escape the heat. This is contributing to childhood obesity and the prospect of a range of diseases in adulthood. When landscape architects and urban designers use a human thermal comfort model to test their designs for children's comfort, they would have to use a model essentially designed to simulate healthy adults. Yet there are many differences between the body of a child and an adult. The aim of this paper was to modify the thermal comfort model COMFA into a children's energy budget model through the consideration of the heat exchange of a child. The energy budget of a child can be up to 21 W/m² higher than adults in hot summertime conditions, and 26 W/m² lower in cold conditions. The model was validated through field studies of 65 children (32 boys and 33 girls) aged from 7-12 years old in 9 days from March to June in 2019, in 68 different microclimates ranging from cool to hot. A 5-point thermal comfort scale of energy budget for children was created using multinomial logistic regression, which revealed that children have a different range of thermal acceptability than adults. The frequency distribution of the actual thermal sensation and the predicted thermal comfort was improved using the new scale. The actual thermal sensation responses from children and the predicted thermal sensation using the model was determined to be positively significantly related. The accuracy of the model was 93.26%. This study has provided an effective children's energy budget model to predict children's thermal comfort. Its application can contribute to the design of thermally comfortable children's outdoor play areas by landscape architects and urban designers.

Pediatric and adolescent injury in aquatic adventure sports

Drowning is a leading cause of death in children. Each year there are thousands of injuries in children, some fatal, associated with aquatic adventure sports. Personal water craft rapidly accelerate children to high velocities, as does being towed behind boats on skis or tubes, whereupon children have no control of their speed or direction. Canoeing and white-water kayaking particularly stress the upper limbs and shoulder dislocations are a primary concern. Surfing and kite-surfing generate more injuries to the head and face than other parts of the body and, in scuba diving, children most frequently injure their ears due to the acute pressure changes experienced. Aquatic injuries cost more in children than in adults and residual functional deficits may last a lifetime. There is a pressing need for research into the prevalence and incidence of aquatic injuries in children, so the effectiveness of preventive interventions can be determined.

Determining temperature ratings for children's cold weather clothing

This study examined the physical and physiological differences between children and adults that affect body heat generation and losses and then developed a heat loss model for determining the temperature ratings of cold weather clothing designed for use by children of various ages. The thermal insulation values of selected jackets were measured using a heated manikin dressed in two base ensembles, and the temperature ratings were calculated using the model. The results indicated that the type of garments used in the base ensemble had a major effect on jacket ensemble insulation and the predicted comfort temperature. For a given level of insulation, the temperature rating decreased as the wearer's age and activity level increased. This is probably because children have a higher surface area per unit mass ratio than adults, and they lose heat faster. However, this effect is partially offset by their higher metabolic rates.

Insulation and Body Temperature of Prepubescent Children Wearing a Thermal Swimsuit During Moderate-Intensity Water Exercise

This study investigated thermal swimsuits (TSS) effects on body temperature and thermal insulation of prepubescent children during moderate-intensity water exercise. Nine prepubescent children (11.0+/-0.7 yrs) were immersed in water (23 degrees C) and pedalled on an underwater cycle-ergometer for 30 min with TSS or normal swimsuits (NSS). The rectal temperature (Tre) was maintained slightly higher with TSS than with NSS. The total insulation (Itotal) was significantly higher with TSS. The DeltaTre, Deltamean body temperature (Tb), and tissue insulation (Itissue) in the NSS condition were correlated with % body fat, which indicated that the insulation layer of subjects with low body fat was thinner than that of obese subjects, and tended to decrease body temperature. Wearing TSS increased Itotal, thereby reducing heat loss from subjects' skin to the water. Consequently, subjects with TSS were able to maintain higher body temperatures. In addition, TSS is especially advantageous for subjects with low body fat to compensate for the smaller Itissue.

Reducing the risk of heat-related decrements to physical activity in young people

The purpose of this review is to highlight differences in thermoregulatory responses during activity of children and adolescents compared with adults. Some differences are due to movement inefficiency and physical size such as body surface area to body mass ratio, and body composition. Identified physiological differences in sweat rates appear to alter with maturation, at least in boys, but the research remains incomplete. A number of findings from hydration studies with young people exercising in the heat are also discussed. The research on clothing is adult-based, but key concepts from this research also apply to children. The final section addresses the limited research on acclimatization of children to hot conditions. Specific recommendations for children who are active in the heat conclude this review.

Regional differences in peripheral vasoconstriction of prepubertal boys

To elucidate the mechanisms that underlie the greater decline of skin temperature on the limbs in prepubertal boys as compared to young men, we compared cutaneous vascular conductance (CVC) of the boys and men in response to a reduced ambient temperature (T (a)). The boys had a greater surface area-to-mass ratio (A (D)/mass) and a lower mean skinfold thickness on the trunk but not on the limbs compared to the men. As T (a) decreased from 30 to 17 degrees C over 60 min, the skin temperature (T (sl)) on the limbs (as represented by forearm, finger and thigh) decreased significantly more in the boys than in the men; while T (sl) on the trunk (chest, back and abdomen) and forehead decreased to the same extent. The CVC decreased at all body sites in all subjects, but regional difference existed in age-related alterations in CVC responses despite the similar rectal and mean body temperatures of the groups. The decline in the finger CVC was greater for the boys than for the men, suggesting that greater vasoconstriction and greater A (D)/mass on the fingers may have contributed to the lower finger T (sl) of the boys. However, thigh CVC in the boys was similar to that in the men over the 60-minute exposure, indicating that the lower thigh T (sl) of the boys may be the result of greater heat loss owing to the greater A (D)/mass on the limbs of the boys (but not to greater vasoconstriction or subcutaneous fat). The CVC on the chest and back was greater in the boys over the cold exposure, suggesting that similar T (sl )on the chest and back of the boys and men may result from greater cooling owing to the larger A (D)/mass being offset by combination of less vasoconstriction and more conductive heat transfer in the presence of less subcutaneous fat. These results suggest that the age-related difference in T (sl) in response to mild cold stress may not directly reflect that in cutaneous vasoconstriction alone owing to the differences in anthropometric characteristics (such as greater A (D)/mass and lower subcutaneous fat on trunk) between boys and men.

Effect of skin sympathetic response to local or systemic cold exposure on thermoregulatory functions in humans

We studied how, sympathetic response to cold exposure determines thermoregulatory function. Three female and seven male volunteers (age, 23.2+/-1.9 years) were exposed to abrupt local cooling and gradual systemic cooling with recording of microneurographic skin sympathetic nerve activity tSSNA), skill temperatures (Ts), tympanic temperature (Tty), skin blood flow measured by laser Doppler flowmetry, and sweating rate measured with a ventilated capsule. Local cooling induced an abrupt vasoconstrictor SSNA increase and Tty rise. There was a significant positive correlation between the increase in the vasoconstrictor SSNA and the change rate of Tty. Systemic cooling at 0.2 degrees C/min enhanced SSNA but gradually decreased Tty, and a significant negative correlation was observed between them. A 10-min delay separated the SSNA rise from the subsequent Tty rise following local cooling. A delay of less than 1 min preceded the SSNA increase after the Tty fall induced by systemic cooling. These findings suggested that subjects with a good SSNA response to cold stress can maintain core temperature, but 10 min is necessary to raise the core temperature by reducing heat loss from the skin surface. In contrast. vasoconstrictor SSNA responds linearly to a fall in core temperature with a delay of less than 1 min.

Clothing microclimate temperatures during thermal comfort in boys, young and older men

To examine the effects of age-related differences in thermoregulatory function on the clothing microclimate temperature (Tm) and Tm fluctuations while maintaining thermal comfort in daily life, 5 boys (group B, 10-11 years), 5 young men (group Y, 20-21 years) and 5 older men (group O, 60-65 years) volunteered to take part in this study. The subjects were asked to maintain thermal comfort as closely as possible in their daily lives. Tm (temperatures between the skin surface and the innermost garment) at four sites (chest, back, upper arm, and thigh), skin temperature on the chest (Tchest) and ambient temperature (Ta) were measured over a period of 8-12 h from morning to evening on one day in each of the seasons, spring, summer, autumn, and winter. Records of ability to maintain thermal comfort and of adjustment of their clothes were kept by each subject. Ta during periods of thermal comfort did not differ among the groups in any of the seasons. In group Y, Tm was significantly lower at the thigh than at the other sites in spring, autumn, and winter (P < 0.05) and fluctuations (CV) of Tm were significantly larger at the thigh than at other sites in autumn and winter (P < 0.05). Similar tendencies were observed for Tm and CV of Tm in group B. However, Tm and CV of Tm in group O did not differ by site except for the autumn Tm. Group O had a smaller CV at the thigh in winter (P < 0.05), compared to groups B and Y, suggesting a smaller regional difference in Tm fluctuation in group O. Group O adjusted their clothes even on the lower limbs (together with upper body) in order to maintain thermal comfort in accordance with changes in Ta, while groups B and Y did so only on their upper bodies. These results suggest that compared to boys and young men, lower thermoregulatory function in older men may affect Tm and CV of Tm as a result of clothing on lower limbs being adjusted differently in order to maintain thermal comfort.