1987, Hormonal, beta-endorphin and renin activity changes in man during partial immersion, as a therapeutic method, in water at 38 degrees C

Digiesi V, Cerchiai G, Forni S, Baldi E, Masi F, Giannotti P.

Minerva Med. 1987 Feb 15;78(3):135-9

https://www.ncbi.nlm.nih.gov/pubmed/2950339