{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,21]],"date-time":"2026-09-21T19:21:19Z","timestamp":1790018479083,"version":"4.0.1"},"reference-count":34,"publisher":"MDPI AG","issue":"5","license":[{"start":{"date-parts":[[2024,5,14]],"date-time":"2024-05-14T00:00:00Z","timestamp":1715644800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Department of Defense, Defense Health Program, Military Operational Medical Research Program Joint Program Committee #5, Military Operational Research Program Aviation Mishap Prevention Program","award":["20G2030.1"],"award-info":[{"award-number":["20G2030.1"]}]},{"name":"Department of Defense, Defense Health Program, Military Operational Medical Research Program Joint Program Committee #5, Military Operational Research Program Aviation Mishap Prevention Program","award":["W911NF22C0029"],"award-info":[{"award-number":["W911NF22C0029"]}]},{"name":"Small Business Technology Transfer Program (STTR) Army Research Office","award":["20G2030.1"],"award-info":[{"award-number":["20G2030.1"]}]},{"name":"Small Business Technology Transfer Program (STTR) Army Research Office","award":["W911NF22C0029"],"award-info":[{"award-number":["W911NF22C0029"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Biology"],"abstract":"<jats:p>Executing flight operations demand that military personnel continuously perform tasks that utilize low- and high-order cognitive functions. The autonomic nervous system (ANS) is crucial for regulating the supply of oxygen (O2) to the brain, but it is unclear how sustained cognitive loads of different complexities may affect this regulation. Therefore, in the current study, ANS responses to low and high cognitive loads in hypoxic and normoxic conditions were evaluated. The present analysis used data from a previously conducted, two-factor experimental design. Healthy subjects (n = 24) aged 19 to 45 years and located near Fort Novosel, AL, participated in the parent study. Over two, 2-h trials, subjects were exposed to hypoxic (14.0% O2) and normoxic (21.0% O2) air while simultaneously performing one, 15-min and one, 10-min simulation incorporating low- and high-cognitive aviation-related tasks, respectively. The tests were alternated across five, 27-min epochs; however, only epochs 2 through 4 were used in the analyses. Heart rate (HR), HR variability (HRV), and arterial O2 saturation were continuously measured using the Warfighter MonitorTM (Tiger Tech Solutions, Inc., Miami, FL, USA), a previously validated armband device equipped with electrocardiographic and pulse oximetry capabilities. Analysis of variance (ANOVA) regression models were performed to compare ANS responses between the low- and high-cognitive-load assessments under hypoxic and normoxic conditions. Pairwise comparisons corrected for familywise error were performed using Tukey\u2019s test within and between high and low cognitive loads under each environmental condition. Across epochs 2 through 4, in both the hypoxic condition and the normoxic condition, the high-cognitive-load assessment (MATB-II) elicited heightened ANS activity, reflected by increased HR (+2.4 \u00b1 6.9 bpm) and decreased HRV (\u2212rMSSD: \u22120.4 \u00b1 2.7 ms and SDNN: \u221213.6 \u00b1 14.6 ms). Conversely, low cognitive load (ADVT) induced an improvement in ANS activity, with reduced HR (\u22122.6 \u00b1 6.3 bpm) and increased HRV (rMSSD: +1.8 \u00b1 6.0 ms and SDNN: vs. +0.7 \u00b1 6.3 ms). Similar observations were found for the normoxic condition, albeit to a lower degree. These within-group ANS responses were significantly different between high and low cognitive loads (HR: +5.0 bpm, 95% CI: 2.1, 7.9, p &lt; 0.0001; rMSSD: \u22122.2 ms, 95% CI: \u22124.2, \u22120.2, p = 0.03; SDNN: \u221214.3 ms, 95% CI: \u221218.4, \u221210.1, p &lt; 0.0001) under the hypoxic condition. For normoxia, significant differences in ANS response were only observed for HR (+4.3 bpm, 95% CI: 1.2, 7.4, p = 0.002). Lastly, only high cognitive loads elicited significant differences between hypoxic and normoxic conditions but just for SDNN (\u221213.3 ms, 95% CI, \u221217.5, \u22128.9, p &lt; 0.0001). Our study observations suggest that compared to low cognitive loads, performing high-cognitive-load tasks significantly alters ANS activity, especially under hypoxic conditions. Accounting for this response is critical, as military personnel during flight operations sustain exposure to high cognitive loads of unpredictable duration and frequency. Additionally, this is likely compounded by the increased ANS activity consequent to pre-flight activities and anticipation of combat-related outcomes.<\/jats:p>","DOI":"10.3390\/biology13050343","type":"journal-article","created":{"date-parts":[[2024,5,15]],"date-time":"2024-05-15T03:35:55Z","timestamp":1715744155000},"page":"343","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":11,"title":["Examining the Influence of Cognitive Load and Environmental Conditions on Autonomic Nervous System Response in Military Aircrew: A Hypoxia\u2013Normoxia Study"],"prefix":"10.3390","volume":"13","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-1244-3699","authenticated-orcid":false,"given":"Harrison L.","family":"Wittels","sequence":"first","affiliation":[{"name":"Tiger Tech Solutions, Inc., Miami, FL 33140, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"S. Howard","family":"Wittels","sequence":"additional","affiliation":[{"name":"Tiger Tech Solutions, Inc., Miami, FL 33140, USA"},{"name":"Department of Anesthesiology, Mount Sinai Medical Center, Miami, FL 33140, USA"},{"name":"Department of Anesthesiology, Wertheim School of Medicine, Florida International University, Miami, FL 33199, USA"},{"name":"Miami Beach Anesthesiology Associates, Miami, FL 33140, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Michael J.","family":"Wishon","sequence":"additional","affiliation":[{"name":"Tiger Tech Solutions, Inc., Miami, FL 33140, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jonathan","family":"Vogl","sequence":"additional","affiliation":[{"name":"Army Aeromedical Research Laboratory, Fort Novosel, AL 36362, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Paul","family":"St. Onge","sequence":"additional","affiliation":[{"name":"Army Aeromedical Research Laboratory, Fort Novosel, AL 36362, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Samantha M.","family":"McDonald","sequence":"additional","affiliation":[{"name":"Tiger Tech Solutions, Inc., Miami, FL 33140, USA"},{"name":"School of Kinesiology and Recreation, Illinois State University, Normal, IL 61761, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4279-7834","authenticated-orcid":false,"given":"Leonard A.","family":"Temme","sequence":"additional","affiliation":[{"name":"Army Aeromedical Research Laboratory, Fort Novosel, AL 36362, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2024,5,14]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"5640784","DOI":"10.1155\/2020\/5640784","article-title":"Cognitive Load Identification of Pilots Based on Physiological-Psychological Characteristics in Complex Environments","volume":"2020","author":"Wang","year":"2020","journal-title":"J. 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