{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,7]],"date-time":"2026-07-07T16:25:01Z","timestamp":1783441501492,"version":"3.54.6"},"reference-count":17,"publisher":"Ovid Technologies (Wolters Kluwer Health)","issue":"3","content-domain":{"domain":["www.ahajournals.org"],"crossmark-restriction":true},"short-container-title":["Hypertension"],"published-print":{"date-parts":[[2022,3]]},"abstract":"<jats:sec>\n            <jats:title>Background:<\/jats:title>\n            <jats:p>Initial orthostatic hypotension (IOH) is defined by a large drop in blood pressure (BP) within 15 s of standing. IOH often presents during an active stand, but not with a passive tilt, suggesting that a muscle activation reflex involving lower body muscles plays an important role. To our knowledge, there is no literature exploring how sympathetic activation affects IOH. We hypothesized involuntary muscle contractions before standing would significantly reduce the drop in BP seen in IOH while increasing sympathetic activity would not.<\/jats:p>\n          <\/jats:sec>\n          <jats:sec>\n            <jats:title>Methods:<\/jats:title>\n            <jats:p>Study participants performed 4 sit-to-stand maneuvers including a mental stress test (serial 7 mental arithmetic stress test), cold pressor test, electrical stimulation, and no intervention. Continuous heart rate and beat-to-beat BP were measured. Cardiac output and systemic vascular resistance were estimated from these waveforms. Data are presented as mean\u00b1SD.<\/jats:p>\n          <\/jats:sec>\n          <jats:sec>\n            <jats:title>Results:<\/jats:title>\n            <jats:p>\n              A total of 23 female IOH participants (31\u00b18 years) completed the study. The drops in systolic BP following the serial 7 mental arithmetic stress test (\u221226\u00b112 mm\u2009Hg;\n              <jats:italic>P<\/jats:italic>\n              =0.004), cold pressor test (\u221220\u00b115 mm\u2009Hg;\n              <jats:italic>P<\/jats:italic>\n              &lt;0.001), and electrical stimulation (\u221228\u00b112 mm\u2009Hg;\n              <jats:italic>P<\/jats:italic>\n              =0.01) were significantly reduced compared with no intervention (\u221234\u00b111 mm\u2009Hg). The drops in systemic vascular resistance following the serial 7 mental arithmetic stress test (\u2212391\u00b1206 dyne\u00d7s\/cm\n              <jats:sup>5<\/jats:sup>\n              ;\n              <jats:italic>P<\/jats:italic>\n              =0.006) and cold pressor test (\u2212386\u00b1179 dyne\u00d7s\/cm\n              <jats:sup>5<\/jats:sup>\n              ;\n              <jats:italic>P<\/jats:italic>\n              =0.011) were significantly reduced compared with no intervention (\u2212488\u00b1173 dyne\u00d7s\/cm\n              <jats:sup>5<\/jats:sup>\n              ). Cardiac output was significantly increased upon standing (7\u00b12 L\/min) compared with during the sit (6\u00b11 L\/min;\n              <jats:italic>P<\/jats:italic>\n              &lt;0.001) for electrical stimulation.\n            <\/jats:p>\n          <\/jats:sec>\n          <jats:sec>\n            <jats:title>Conclusion:<\/jats:title>\n            <jats:p>Sympathetic activation mitigates the BP response in IOH, while involuntary muscle contraction mitigates the BP response and reduces symptoms. Active muscle contractions may induce both of these mechanisms of action in their pretreatment of IOH.<\/jats:p>\n          <\/jats:sec>\n          <jats:sec>\n            <jats:title>Registration:<\/jats:title>\n            <jats:p>\n              URL:\n              <jats:ext-link xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" ext-link-type=\"uri\" xlink:href=\"https:\/\/www.clinicaltrials.gov\">https:\/\/www.clinicaltrials.gov<\/jats:ext-link>\n              ; Unique identifier: NCT03970551.\n            <\/jats:p>\n          <\/jats:sec>","DOI":"10.1161\/hypertensionaha.121.18580","type":"journal-article","created":{"date-parts":[[2022,1,6]],"date-time":"2022-01-06T19:06:57Z","timestamp":1641496017000},"page":"638-647","update-policy":"https:\/\/doi.org\/10.1161\/crossmarkpolicy","source":"Crossref","is-referenced-by-count":17,"title":["Mitigating Initial Orthostatic Hypotension: Mechanistic Roles of Muscle Contraction Versus Sympathetic Activation"],"prefix":"10.1161","volume":"79","clinical-trial-number":[{"clinical-trial-number":"nct03970551","registry":"10.18810\/clinical-trials-gov"}],"author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-3906-2327","authenticated-orcid":true,"given":"Nasia A.","family":"Sheikh","sequence":"first","affiliation":[{"name":"Department of Cardiac Sciences, Libin Cardiovascular Institute, Cumming School of Medicine (N.A.S., A.A.P., S.R., M.L., K.K., K.M.B., J.G.J., L.Y.L., R.S.S., D.V.E., S.R.R.), University of Calgary, AB, Canada."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Aaron A.","family":"Phillips","sequence":"additional","affiliation":[{"name":"Department of Cardiac Sciences, Libin Cardiovascular Institute, Cumming School of Medicine (N.A.S., A.A.P., S.R., M.L., K.K., K.M.B., J.G.J., L.Y.L., R.S.S., D.V.E., S.R.R.), University of Calgary, AB, Canada."},{"name":"Departments of Physiology and Pharmacology and Clinical Neuroscience (A.A.P.), University of Calgary, AB, Canada."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Shaun","family":"Ranada","sequence":"additional","affiliation":[{"name":"Department of Cardiac Sciences, Libin Cardiovascular Institute, Cumming School of Medicine (N.A.S., A.A.P., S.R., M.L., K.K., K.M.B., J.G.J., L.Y.L., R.S.S., D.V.E., S.R.R.), University of Calgary, AB, Canada."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Matthew","family":"Lloyd","sequence":"additional","affiliation":[{"name":"Department of Cardiac Sciences, Libin Cardiovascular Institute, Cumming School of Medicine (N.A.S., A.A.P., S.R., M.L., K.K., K.M.B., J.G.J., L.Y.L., R.S.S., D.V.E., S.R.R.), University of Calgary, AB, Canada."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Karolina","family":"Kogut","sequence":"additional","affiliation":[{"name":"Department of Cardiac Sciences, Libin Cardiovascular Institute, Cumming School of Medicine (N.A.S., A.A.P., S.R., M.L., K.K., K.M.B., J.G.J., L.Y.L., R.S.S., D.V.E., S.R.R.), University of Calgary, AB, Canada."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8355-0002","authenticated-orcid":true,"given":"Kate M.","family":"Bourne","sequence":"additional","affiliation":[{"name":"Department of Cardiac Sciences, Libin Cardiovascular Institute, Cumming School of Medicine (N.A.S., A.A.P., S.R., M.L., K.K., K.M.B., J.G.J., L.Y.L., R.S.S., D.V.E., S.R.R.), University of Calgary, AB, Canada."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6012-0122","authenticated-orcid":true,"given":"Juliana G.","family":"Jorge","sequence":"additional","affiliation":[{"name":"Department of Cardiac Sciences, Libin Cardiovascular Institute, Cumming School of Medicine (N.A.S., A.A.P., S.R., M.L., K.K., K.M.B., J.G.J., L.Y.L., R.S.S., D.V.E., S.R.R.), University of Calgary, AB, Canada."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4036-7697","authenticated-orcid":true,"given":"Lucy Y.","family":"Lei","sequence":"additional","affiliation":[{"name":"Department of Cardiac Sciences, Libin Cardiovascular Institute, Cumming School of Medicine (N.A.S., A.A.P., S.R., M.L., K.K., K.M.B., J.G.J., L.Y.L., R.S.S., D.V.E., S.R.R.), University of Calgary, AB, Canada."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3463-4082","authenticated-orcid":true,"given":"Robert S.","family":"Sheldon","sequence":"additional","affiliation":[{"name":"Department of Cardiac Sciences, Libin Cardiovascular Institute, Cumming School of Medicine (N.A.S., A.A.P., S.R., M.L., K.K., K.M.B., J.G.J., L.Y.L., R.S.S., D.V.E., S.R.R.), University of Calgary, AB, Canada."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Derek V.","family":"Exner","sequence":"additional","affiliation":[{"name":"Department of Cardiac Sciences, Libin Cardiovascular Institute, Cumming School of Medicine (N.A.S., A.A.P., S.R., M.L., K.K., K.M.B., J.G.J., L.Y.L., R.S.S., D.V.E., S.R.R.), University of Calgary, AB, Canada."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mary","family":"Runte","sequence":"additional","affiliation":[{"name":"Department of Management, University of Lethbridge, Alberta, Canada (M.R.)."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5890-3785","authenticated-orcid":true,"given":"Satish R.","family":"Raj","sequence":"additional","affiliation":[{"name":"Department of Cardiac Sciences, Libin Cardiovascular Institute, Cumming School of Medicine (N.A.S., A.A.P., S.R., M.L., K.K., K.M.B., J.G.J., L.Y.L., R.S.S., D.V.E., S.R.R.), University of Calgary, AB, Canada."},{"name":"Division of Clinical Pharmacology, Department of Medicine, Autonomic Dysfunction Center, Vanderbilt University Medical Center, Nashville, TN (S.R.R.)."}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"276","reference":[{"key":"e_1_3_2_2_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.jash.2015.02.006"},{"key":"e_1_3_2_3_2","doi-asserted-by":"publisher","DOI":"10.1042\/CS20060091"},{"key":"e_1_3_2_4_2","doi-asserted-by":"publisher","DOI":"10.1152\/ajpheart.00571.2011"},{"key":"e_1_3_2_5_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.ijcard.2018.05.043"},{"key":"e_1_3_2_6_2","doi-asserted-by":"publisher","DOI":"10.1111\/j.1475-097x.1996.tb00565.x"},{"key":"e_1_3_2_7_2","doi-asserted-by":"publisher","DOI":"10.1007\/s12576-019-00669-6"},{"key":"e_1_3_2_8_2","first-page":"30:453","article-title":"Activating lower body muscles prior to standing mitigates symptoms of initial orthostatic hypotension.","author":"Sheikh N","year":"2020","unstructured":"Sheikh, N, Ranada, S, Lloyd, M, McCarthy, D, Sheldon, RS, Phillips, AA, Exner, DV, Runte, 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