Effects of physical activity and shade on the heat balance and thermal perceptions of children in a playground microclimate

Abstract

Outdoor thermal comfort (TC) is an important parameter in assessing the value and health utility of a recreational space. Given the public health significance of child heat illness, the ability to model children's heat balance and TC during activity has received little attention. The current pilot study tests the performance of an outdoor human heat balance model on children playing in warm/hot outdoor environments in sun and shade. Fourteen children aged 9e13 participated in the 8-day study in Texas in spring 2016, performing physical activity while wearing heartrate monitors and completing thermal perception surveys (e.g., actual thermal sensation (ATS)). Surveys were compared to predicted thermal sensation (PTS) based on principles of human-environment heat exchange using personal data and a suite of on-site microclimate information. Results demonstrate the model to significantly predict ATS votes (Spearman's rho ¼ 0.504). Subjective preferred change was also significantly correlated to modeled PTS (rho ¼ À0.607). Radiation, air temperature, windspeed, and level of tiredness were significant predictors of ATS. Finally, the mean human energy balance was significantly lower in the shade (À168 W m-2), thus lowering heat stress potential, with the model predicting ATS with little-to-no error (0.2 and 0.0 scale error units in sun and shade, respectively). This study demonstrates an ability to estimate a child's heat balance while accounting for changes in major heat contributors (e.g., radiation, metabolism), and is the first study to evaluate TC of children during activity in outdoor built environments. New insights of heat perception may aid in recognition of often under-recognized heat stress.

Heat strain in children during unstructured outdoor physical activity in a continental summer climate

“…Previous work in children during outdoor physical activity suggested that they may not demonstrate the capacity to make appropriate behavioral adjustments (e.g. self-pacing, reducing work effort and/ or interspersing more rest breaks) based on their perception of heat strain [25]. However, reports in adult workers show they may suffer excessive heat strain and heat stroke even when self-pacing is permitted [26].…”

Outdoor Thermal Comfort during Anomalous Heat at the 2015 Pan American Games in Toronto, Canada

“…The HR estimates collected in Texas are assumed to be similar to those experienced by a soccer player at the PA15 Games and provide a much more realistic estimate of average metabolic intensities of soccer players in normal game situations. Analogous to the energy expenditure estimation methods [56,57], inputs of age (25 years of age), average resting HR, activity HR, and gender were used to estimate the energy expenditure of a female or male midfielder, and output in METs (1 MET = 58.15 Wm −2 ).…”

Microclimate Variation and Estimated Heat Stress of Runners in the 2020 Tokyo Olympic Marathon

“…The full detailed methods are found in Hardin and Vanos (2017) and Kenny (2008) [33,34]. Below, we outline any changes made from studies [21,28,32] for the given study. The outgoing longwave (L out ) radiation was determined from the measured ground temperature and the use of the Stephan-Boltzmann equation.…”

“…An average metabolism of~700 W m −2 was determined by allowing for energy to be converted to mechanical work during running, where the net gain from metabolism, M, is 0.8M total + 0.2M rest [30], where M rest is 1 MET (58 W m −2 ) and M total is based on running at an average speed of 18 km h −1 for an elite runner, or 14.5 METs [31]. The influence of an increased relative wind velocity of the runner to promote cooling via decreased resistance to vapor and heat transfer from higher wind is also determined by the COMFA model (see [21,28,32]). …”