{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,30]],"date-time":"2026-07-30T11:10:27Z","timestamp":1785409827694,"version":"3.56.0"},"reference-count":48,"publisher":"MDPI AG","issue":"11","license":[{"start":{"date-parts":[[2026,6,5]],"date-time":"2026-06-05T00:00:00Z","timestamp":1780617600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100009898","name":"Defense Health Agency","doi-asserted-by":"crossref","award":["#47QFWA20C0012"],"award-info":[{"award-number":["#47QFWA20C0012"]}],"id":[{"id":"10.13039\/100009898","id-type":"DOI","asserted-by":"crossref"}]},{"DOI":"10.13039\/100009898","name":"Defense Health Agency","doi-asserted-by":"crossref","award":["#HT942524C0053"],"award-info":[{"award-number":["#HT942524C0053"]}],"id":[{"id":"10.13039\/100009898","id-type":"DOI","asserted-by":"crossref"}]},{"award":["#47QFWA20C0012"],"award-info":[{"award-number":["#47QFWA20C0012"]}],"id":[{"id":"https:\/\/ror.org\/03df8gj37","id-type":"ROR","asserted-by":"publisher"}]},{"award":["#HT942524C0053"],"award-info":[{"award-number":["#HT942524C0053"]}],"id":[{"id":"https:\/\/ror.org\/03df8gj37","id-type":"ROR","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Assessing task workload during military En Route Critical Care (ERCC) and other high-risk clinical operations remains challenging. This study evaluated heart rate variability (HRV) and body motion as digital biomarkers of task workload among Critical Care Air Transport (CCAT) teams during simulated ERCC missions. Seventy-two U.S. Air Force clinicians participated in 26 high-fidelity simulations. HRV and body motion were continuously captured via a chest-strap wearable sensor, and the NASA Task Load Index (NASA-TLX) was used to assess self-reported workload. Results demonstrated high feasibility (&gt;90% HRV, 100% motion retention) with high wearable comfort ratings. Both HRV and Motion metrics showed strong construct validity, significantly differentiating resting baseline from active simulation (all p &lt; 0.001, effect sizes d = 0.54\u20131.22 for HRV, r = 0.92\u20131.00 for motion). Convergent validity was selective: only baseline-adjusted root mean square of successive differences (RMSSD) demonstrated significant associations with NASA-TLX mental demand (\u03b2 = \u22120.250, p = 0.005) and temporal demand (\u03b2 = \u22120.233, p = 0.003). Baseline-adjusted RMSSD effectively indexes perceived workload, while Motion metrics provide complementary information about physical task demands. These findings support multimodal approaches integrating physiological reactivity, motion patterns, and self-reported ratings for comprehensive workload assessment in complex operational settings.<\/jats:p>","DOI":"10.3390\/s26113596","type":"journal-article","created":{"date-parts":[[2026,6,5]],"date-time":"2026-06-05T08:43:04Z","timestamp":1780648984000},"page":"3596","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Heart Rate Variability and Body Motion as Digital Biomarkers of Task Workload During Military En Route Critical Care Simulations"],"prefix":"10.3390","volume":"26","author":[{"given":"Roger D.","family":"Dias","sequence":"first","affiliation":[{"name":"Department of Emergency Medicine, Harvard Medical School, Boston, MA 02115, USA"},{"name":"Medical AI and Cognitive Engineering (MAICE) Lab, STRATUS Center for Medical Simulation, Mass General Brigham, Boston, MA 02115, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0077-6282","authenticated-orcid":false,"given":"Sarah H.","family":"Michael","sequence":"additional","affiliation":[{"name":"Center for COMBAT Research, Medical Campus, University of Colorado Anschutz, Aurora, CO 80045, USA"},{"name":"Department of Emergency Medicine, School of Medicine, University of Colorado Anschutz, Aurora, CO 80045, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Rayan","family":"Harari","sequence":"additional","affiliation":[{"name":"Department of Emergency Medicine, Harvard Medical School, Boston, MA 02115, USA"},{"name":"Medical AI and Cognitive Engineering (MAICE) Lab, STRATUS Center for Medical Simulation, Mass General Brigham, Boston, MA 02115, USA"},{"name":"Department of Radiology, Mass General Brigham, Boston, MA 02115, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9889-9090","authenticated-orcid":false,"given":"Steven","family":"Yule","sequence":"additional","affiliation":[{"name":"Surgical Sabermetrics Laboratory, Usher Institute, University of Edinburgh, Scotland EH16 4TJ, UK"},{"name":"Department of Clinical Surgery, University of Edinburgh\/Royal Infirmary of Edinburgh, Scotland EH16 4TJ, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Lance","family":"McGinnis","sequence":"additional","affiliation":[{"name":"Nursing Research Division, 59th Medical Wing Science and Technology, JBSA-Lackland, San Antonio, TX 78236, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Richard J. E.","family":"Skipworth","sequence":"additional","affiliation":[{"name":"Surgical Sabermetrics Laboratory, Usher Institute, University of Edinburgh, Scotland EH16 4TJ, UK"},{"name":"Department of Clinical Surgery, University of Edinburgh\/Royal Infirmary of Edinburgh, Scotland EH16 4TJ, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Elizabeth","family":"Mann-Salinas","sequence":"additional","affiliation":[{"name":"En Route Care Research Center, 59th Medical Wing Science and Technology, San Antonio, TX 78234, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"William T.","family":"Davis","sequence":"additional","affiliation":[{"name":"En Route Care Research Center, 59th Medical Wing Science and Technology, San Antonio, TX 78234, USA"},{"name":"Department of Emergency Medicine, Brooke Army Medical Center, San Antonio, TX 78234, USA"},{"name":"Department of Military and Emergency Medicine, Uniformed Services University, Bethesda, MD 20814, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,6,5]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"19","DOI":"10.7205\/MILMED-D-13-00240","article-title":"Effective Teamwork and Communication Mitigate Task Saturation in Simulated Critical Care Air Transport Team Missions","volume":"179","author":"Davis","year":"2014","journal-title":"Mil. 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