{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,8]],"date-time":"2026-05-08T01:10:18Z","timestamp":1778202618359,"version":"3.51.4"},"reference-count":49,"publisher":"Wiley","license":[{"start":{"date-parts":[[2026,5,7]],"date-time":"2026-05-07T00:00:00Z","timestamp":1778112000000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"},{"start":{"date-parts":[[2026,5,7]],"date-time":"2026-05-07T00:00:00Z","timestamp":1778112000000},"content-version":"tdm","delay-in-days":0,"URL":"http:\/\/doi.wiley.com\/10.1002\/tdm_license_1.1"}],"content-domain":{"domain":["physoc.onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["Experimental Physiology"],"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:p>\n                    High\u2010altitude exposure increases haemoglobin mass (Hb\n                    <jats:sub>mass<\/jats:sub>\n                    ), a key determinant of arterial oxygen\u2010carrying capacity, but following descent this adaptation can regress toward baseline within 7\u00a0days. Long\u2010term heat acclimation has emerged as an alternative stimulus for Hb\n                    <jats:sub>mass<\/jats:sub>\n                    expansion; however, whether post\u2010altitude passive\u2010heat exposure can preserve altitude\u2010induced increases in Hb\n                    <jats:sub>mass<\/jats:sub>\n                    remains unclear. Furthermore, the extent to which any preservation of Hb\n                    <jats:sub>mass<\/jats:sub>\n                    is supported by sustained erythropoietin (EPO) production, and whether this support is mediated by plasma volume expansion or acute alterations in renal haemodynamics, has yet to be explored. Twenty\u2010one healthy adults (8F) sojourned at 3800\u00a0m for 14\u00a0days and, following descent to 1250\u00a0m, were allocated to either hot\u2010water immersion (HWI; 45\u00a0min at 40\u00b0C for 4\u00a0days;\u00a0\n                    <jats:italic>n\u00a0<\/jats:italic>\n                    =\u00a011) or control (CON;\u00a0\n                    <jats:italic>n\u00a0<\/jats:italic>\n                    =\u00a010). Hb\n                    <jats:sub>mass<\/jats:sub>\n                    , intravascular volumes (carbon monoxide rebreathing) and circulating EPO were measured on high\u2010altitude day 1 (HA1), day 14 (HA14), and post\u2010descent day 5 (P5). Renal\u2010artery blood velocity (Doppler\u2010ultrasound) was measured before and after HWI on the day of descent. Hb\n                    <jats:sub>mass<\/jats:sub>\n                    increased by 24\u00a0g [95% CI: 8, 40] across all participants during the altitude sojourn (\n                    <jats:italic>P\u00a0<\/jats:italic>\n                    =\u00a00.005). Following descent, Hb\n                    <jats:sub>mass<\/jats:sub>\n                    decreased in CON (\u2206\u00a0=\u00a0\u221218\u00a0g [95% CI: \u221236, 0],\u00a0\n                    <jats:italic>P\u00a0<\/jats:italic>\n                    =\u00a00.045) but was maintained in HWI (\u2206\u00a0=\u00a0+9\u00a0g [95% CI: \u22128, 26],\u00a0\n                    <jats:italic>P\u00a0<\/jats:italic>\n                    =\u00a00.285). Circulating EPO declined after descent (\n                    <jats:italic>P\u00a0<\/jats:italic>\n                    &lt;\u00a00.001) with no between\u2010condition difference at P5 (\n                    <jats:italic>P\u00a0<\/jats:italic>\n                    =\u00a00.239), despite a transient reduction in renal\u2010artery blood velocity following HWI (\n                    <jats:italic>P\u00a0<\/jats:italic>\n                    =\u00a00.025) and similar plasma volume expansion across groups (time:\u00a0\n                    <jats:italic>P\u00a0<\/jats:italic>\n                    &lt;\u00a00.001). Hot\u2010water immersion offers a practical, lower\u2010impact alternative to exercise\u2010heat methods for preserving altitude\u2010derived Hb\n                    <jats:sub>mass<\/jats:sub>\n                    expansion, although the mechanisms underlying this response remain elusive.\n                  <\/jats:p>","DOI":"10.1113\/ep093944","type":"journal-article","created":{"date-parts":[[2026,5,8]],"date-time":"2026-05-08T00:30:48Z","timestamp":1778200248000},"update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Daily hot\u2010water immersion preserves altitude\u2010induced haemoglobin mass expansion following descent independent of erythropoietin"],"prefix":"10.1113","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-4053-2410","authenticated-orcid":false,"given":"Elliott J.","family":"Jenkins","sequence":"first","affiliation":[{"name":"Cardiff School of Sport and Health Sciences Cardiff Metropolitan University  Cardiff UK"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jodie L.","family":"Koep","sequence":"additional","affiliation":[{"name":"Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences University of British Columbia Okanagan Campus  Kelowna Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2965-6081","authenticated-orcid":false,"given":"Andrew J. M.","family":"Douglas","sequence":"additional","affiliation":[{"name":"Cardiff School of Sport and Health Sciences Cardiff Metropolitan University  Cardiff UK"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Lauren E.","family":"Maier","sequence":"additional","affiliation":[{"name":"Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences University of British Columbia Okanagan Campus  Kelowna Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1133-2444","authenticated-orcid":false,"given":"Connor A.","family":"Howe","sequence":"additional","affiliation":[{"name":"Institute of Sport Science University of Innsbruck  Innsbruck Austria"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Sarah","family":"Sheitelman","sequence":"additional","affiliation":[{"name":"Department of Biological Sciences Northern Arizona University  Flagstaff Arizona USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Liam D.","family":"Corr","sequence":"additional","affiliation":[{"name":"Cardiff School of Sport and Health Sciences Cardiff Metropolitan University  Cardiff UK"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Christoph","family":"Siebenmann","sequence":"additional","affiliation":[{"name":"Institute of Mountain Emergency Medicine, EURAC Research  Bolzano Italy"},{"name":"Hochgebirgsklinik Davos, Medicine Campus Davos  Davos Switzerland"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Michael G.","family":"Hughes","sequence":"additional","affiliation":[{"name":"Cardiff School of Sport and Health Sciences Cardiff Metropolitan University  Cardiff UK"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1667-294X","authenticated-orcid":false,"given":"Joshua C.","family":"Tremblay","sequence":"additional","affiliation":[{"name":"Cardiff School of 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