2012, Passive heat exposure induced by hot water leg immersion increased oxyhemoglobin in pre-frontal cortex to preserve oxygenation and did not contribute to impaired cognitive functioning

Wijayanto T, Toramoto S, Tochihara Y

Int J Biometeorol. 2013 Jul;57(4):557-67. doi: 10.1007/s00484-012-0583-1. Epub 2012 Aug 18

https://www.ncbi.nlm.nih.gov/pubmed/22898999