{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,30]],"date-time":"2026-09-30T18:22:58Z","timestamp":1790792578036,"version":"4.1.0"},"reference-count":40,"publisher":"Wiley","issue":"15","license":[{"start":{"date-parts":[[2024,8,6]],"date-time":"2024-08-06T00:00:00Z","timestamp":1722902400000},"content-version":"vor","delay-in-days":5,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100000049","name":"National Institute on Aging","doi-asserted-by":"publisher","award":["AG069005"],"award-info":[{"award-number":["AG069005"]}],"id":[{"id":"10.13039\/100000049","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100006751","name":"U.S. Army","doi-asserted-by":"publisher","award":["W81XWH\u201012\u20101\u20100152"],"award-info":[{"award-number":["W81XWH\u201012\u20101\u20100152"]}],"id":[{"id":"10.13039\/100006751","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["physoc.onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["Physiological Reports"],"published-print":{"date-parts":[[2024,8]]},"abstract":"<jats:title>Abstract<\/jats:title><jats:p>The compensatory reserve index (CRI), derived from machine learning algorithms from peripherally obtained photoplethysmography signals, provides a non\u2010invasive assessment of cardiovascular stability, that may be useful clinically. Briefly, the CRI device provides a value between 0 and 1, with 1 reflecting full compensable capabilities and 0 reflecting little to no compensable capabilities. However, the CRI algorithm was developed in younger to middle aged adults, such that it is unknown if older age modulates CRI responses to cardiovascular challenges. In young and older subjects, we compared CRI responses to normothermic and hyperthermic progressive lower body negative pressure (LBNP), and volume loading with saline infusion. Eleven younger (20\u201336\u2009years) and 10 older (61\u201375\u2009years) healthy participants underwent (1) graded normothermic LBNP up to 30\u2009mmHg, (2) graded hyperthermic (1.5\u00b0C increase in blood temperature) LBNP up to 30\u2009mmHg, and (3) infusion of 15\u2009mL\/kg saline (volume loading) with hyperthermia maintained. CRI was obtained throughout each procedure. CRI at 30\u2009mmHg LBNP was 0.18 and 0.24\u2009units greater in the older group during normothermic and hyperthermic LBNP, respectively. However, CRI was not different between age groups at any other LBNP stage, nor did CRI change with volume loading regardless of age. In response to passive hyperthermia alone, regression analyses showed that heart rate was the strongest predictor of CRI. Blood temperature, rate pressure product, and stroke volume were also predictive of CRI but to a lesser extent. In conclusion, age attenuates the reduction in CRI during progressive normothermic and hyperthermic LBNP, but only at 30\u2009mmHg. Second, the CRI was unchanged during volume loading in all subjects. Future studies should determine whether the age differences in CRI reflect age differences in LBNP tolerance.<\/jats:p>","DOI":"10.14814\/phy2.16177","type":"journal-article","created":{"date-parts":[[2024,8,7]],"date-time":"2024-08-07T02:39:07Z","timestamp":1722998347000},"update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":2,"title":["Compensatory reserve index during central hypovolemia and volume loading in healthy young and older hyperthermic adults: A pilot study"],"prefix":"10.14814","volume":"12","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-6232-9336","authenticated-orcid":false,"given":"Josh","family":"Foster","sequence":"first","affiliation":[{"name":"Institute for Exercise and Environmental Medicine Texas Health Presbyterian Hospital Dallas, University of Texas Southwestern Medical Center  Dallas Texas USA"},{"name":"Centre for Human and Applied Physiological Sciences, Faculty of Life Sciences and Medicine King's College London  London UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Daniel","family":"Gagnon","sequence":"additional","affiliation":[{"name":"Institute for Exercise and Environmental Medicine Texas Health Presbyterian Hospital Dallas, University of Texas Southwestern Medical Center  Dallas Texas USA"},{"name":"Montreal Heart Institute and School of Kinesiology and Exercise Science Universit\u00e9 de Montr\u00e9al  Montreal Quebec Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Caitlin P.","family":"Jarrard","sequence":"additional","affiliation":[{"name":"Institute for Exercise and Environmental Medicine Texas Health Presbyterian Hospital Dallas, University of Texas Southwestern Medical Center  Dallas Texas USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Whitley C.","family":"Atkins","sequence":"additional","affiliation":[{"name":"Institute for Exercise and Environmental Medicine Texas Health Presbyterian Hospital Dallas, University of Texas Southwestern Medical Center  Dallas Texas USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Zachary","family":"McKenna","sequence":"additional","affiliation":[{"name":"Institute for Exercise and Environmental Medicine Texas Health Presbyterian Hospital Dallas, University of Texas Southwestern Medical Center  Dallas Texas USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Steven A.","family":"Romero","sequence":"additional","affiliation":[{"name":"Institute for Exercise and Environmental Medicine Texas Health Presbyterian Hospital Dallas, University of Texas Southwestern Medical Center  Dallas Texas USA"},{"name":"Department of Physiology and Anatomy University of North Texas Health Science Center  Fort Worth Texas USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7792-9713","authenticated-orcid":false,"given":"Craig G.","family":"Crandall","sequence":"additional","affiliation":[{"name":"Institute for Exercise and Environmental Medicine Texas Health Presbyterian Hospital Dallas, University of Texas Southwestern Medical Center  Dallas Texas USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"311","published-online":{"date-parts":[[2024,8,6]]},"reference":[{"key":"e_1_2_7_2_1","first-page":"H92","article-title":"Plasma volumes and hematocrits in rats with chronic sinoaortic denervation hypertension","volume":"236","author":"Alexander N.","year":"1979","journal-title":"The American Journal of Physiology"},{"key":"e_1_2_7_3_1","doi-asserted-by":"publisher","DOI":"10.1113\/jphysiol.1945.sp004113"},{"key":"e_1_2_7_4_1","doi-asserted-by":"publisher","DOI":"10.1093\/milmed\/149.2.55"},{"key":"e_1_2_7_5_1","doi-asserted-by":"publisher","DOI":"10.1097\/TA.0000000000001474"},{"key":"e_1_2_7_6_1","doi-asserted-by":"publisher","DOI":"10.1152\/ajpregu.00223.2018"},{"key":"e_1_2_7_7_1","doi-asserted-by":"publisher","DOI":"10.1113\/jphysiol.2010.191981"},{"key":"e_1_2_7_8_1","doi-asserted-by":"publisher","DOI":"10.1111\/trf.16494"},{"issue":"442","key":"e_1_2_7_9_1","first-page":"2018","article-title":"Wearable technology for compensatory reserve to sense hypovolemia","volume":"124","author":"Convertino V. 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