Thermal comfort modelling of body temperature and psychological variations of a human exercising in an outdoor environment

Human thermal comfort assessments pertaining to exercise while in outdoor environments can improve urban and recreational planning. The current study applied a simple four-segment skin temperature approach to the COMFA (COMfort FormulA) outdoor energy balance model. Comparative results of measured mean skin temperature ( [`(T)]nolimits<sub>Msk</sub> mathop{{bar{T}}}nolimits_{{Msk}} ) with predicted [`(T)]nolimits_sk mathop{{bar{T}}}nolimits_{{sk}} indicate that the model accurately predicted [`(T)]nolimits<sub>sk</sub> mathop{{bar{T}}}nolimits_{{sk}} , showing significantly strong agreement (r = 0.859, P < 0.01) during outdoor exercise (cycling and running). The combined 5-min mean variation of the [`(T)]nolimits_sk mathop{{bar{T}}}nolimits_{{sk}} RMSE was 1.5°C, with separate cycling and running giving RMSE of 1.4°C and 1.6°C, respectively, and no significant difference in residuals. Subjects’ actual thermal sensation (ATS) votes displayed significant strong rank correlation with budget scores calculated using both measured and predicted [`(T)]nolimits<sub>sk</sub> mathop{{bar{T}}}nolimits_{{sk}} (r <sub>s</sub>  = 0.507 and 0.517, respectively, P < 0.01). These results show improved predictive strength of ATS of subjects as compared to the original and updated COMFA models. This psychological improvement, plus [`(T)]nolimits_sk mathop{{bar{T}}}nolimits_{{sk}} and T _c validations, enables better application to a variety of outdoor spaces. This model can be used in future research studying linkages between thermal discomfort, subsequent decreases in physical activity, and negative health trends.