Body temperature and psychological variations during thermal comfort modelling of a human exercising in an outdoor environment

Concern over the rise of urban air temperatures and decreased physical activity has illuminated the importance of outdoor human comfort modelling during exercise. Human biometeorology assessments pertaining to exercise in urban areas can improve urban planning and recreation, with an overarching goal of improving human health. The lack of accurate predictions of actual thermal sensation (ATS) reported by individuals is a weakness in modelling, attributed to individual psychological and physiological differences. There are conflicting contributions from mean skin temperature and internal core temperature, as well as in the magnitude of change in the local skin temperature distribution. The aim of this study was to verify and improve the accuracy of skin and core temperature predictions in the COMFA (COMfort FormulA) outdoor model to reduce errors in energy budget predictions. Field tests were conducted on subjects performing 30 minutes of steady-state physical activity (running or cycling). The predicted thermal sensations (PTS) from the COMFA budget model using both predicted (with model) and actual (measured) skin temperatures were compared in 5-minute intervals. Results indicate that the model over-predicted skin temperature throughout the exercise period, particularly when metabolic rate was high, as well as on cooler and cloudy days. Results of Spearman's rank correlation analysis displayed ATS votes correlating to a greater extent with PTS by the model. Additionally, ATS votes correlated more strongly with PTS scores during running tests (cooler days), showing that responses were more difficult to predict as temperature increased and/or with cycling rather than running. These results illustrate the inherent difficulty of using thermal comfort models during outdoor exercise due to added variables outdoors, as well as inter-individual psychological/physiological variations. Further research into accurate modelling is needed for the application of climate sensitive urban design for creation of thermally comfortable outdoor urban spaces. These are needed to provide more satisfactory spaces for exercise and recreational activities, which increases the overall health and well-being of urban dwellers.