Response to Simpson (2024): Standard heat stress indices may not be appropriate for assessing marathons

Abstract

We value comments on our research paper in a Commentary in this issue (Simpson, S Afr J Sci. 2024;120(1/2), Art. #16445). Acknowledging the Universal Thermal Comfort Index (UTCI)'s limitations in capturing individual physiological responses remains important; however, we argue for its appropriateness based on recent thermophysiology and heat exchange advancements during its development and broader alignment with standardised indexing efforts. Our original research paper set out with these considerations in mind, and our conclusions remain valid. We further argue for refinement of the UTCI for specific activities instead of using the PET. Finally, future efforts should focus on monitoring data in real-world scenarios to validate and improve thermal indices.