{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,25]],"date-time":"2026-09-25T19:12:48Z","timestamp":1790363568128,"version":"4.1.0"},"reference-count":41,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2025,4,29]],"date-time":"2025-04-29T00:00:00Z","timestamp":1745884800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100004326","name":"Simon Fraser University","doi-asserted-by":"publisher","id":[{"id":"10.13039\/501100004326","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Physiol."],"abstract":"<jats:sec><jats:title>Introduction<\/jats:title><jats:p>Baroreflex-mediated activation of lower leg muscles (i.e., muscle-pump baroreflex) has been suggested to play a significant role in blood pressure regulation during standing. Compromised muscle-pump baroreflex because of ageing or prolonged inactivity could contribute to orthostatic hypotension. Understanding the contribution of individual lower leg muscles to blood pressure regulation could lead to the development of muscle-specific strategies to prevent orthostatic hypotension associated with muscle-pump baroreflex dysfunctions.<\/jats:p><\/jats:sec><jats:sec><jats:title>Methods<\/jats:title><jats:p>In this study, individual muscle (tibialis anterior (TA), lateral soleus (SOL), medial gastrocnemius (MG), and lateral gastrocnemius (LG)) responses to blood pressure changes upon a supine-to-stand orthostatic challenge were examined in young adult male participants (35 \u00b1 2 years) before and after 60 days of 6\u00b0 head-down tilt bed rest (HDBR). By analyzing the interactions between systolic blood pressure (SBP) and heartbeat-by-heartbeat electromyogram impulse (EMG<jats:sub>imp<\/jats:sub>) during standing, the interactions between SBP and EMGimp including muscle-pump baroreflex were characterized by fraction time active (FTA) and response gain from wavelet transform coherence analysis and the causality values using convergent cross mapping method for individual leg muscles. Since inactivity and ageing are common causes of orthostatic intolerance, the HDBR results were compared with those from young and older individuals in a previously published study to investigate the similarities in their effects on muscle-pump baroreflex.<\/jats:p><\/jats:sec><jats:sec><jats:title>Results<\/jats:title><jats:p>During standing, FTA reduced for all muscles except MG following HDBR and was lower in older compared to younger participants. Muscle-pump baroreflex causality (SBP\u2192EMG<jats:sub>imp<\/jats:sub>) reduced for all muscles following HDBR and was lower for LG and SOL muscles in older compared to younger adults. The mechanical muscle-pump causality (SBP\u2192EMG<jats:sub>imp<\/jats:sub>) was not affected by HDBR or by age. Increased TA muscle-pump baroreflex gain post-HDBR may point to a compensatory mechanism for decreased active control.<\/jats:p><\/jats:sec><jats:sec><jats:title>Conclusions<\/jats:title><jats:p>Our results showed striking similarities in the alteration of muscle-pump baroreflex induced via ageing and HDBR, suggesting strong commonalities between ageing and long-term inactivity in terms of the adverse effects on baroreflex mediated control of lower leg muscle activities in response to orthostatic challenge.<\/jats:p><\/jats:sec>","DOI":"10.3389\/fphys.2025.1426648","type":"journal-article","created":{"date-parts":[[2025,4,29]],"date-time":"2025-04-29T04:10:38Z","timestamp":1745899838000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":4,"title":["Alterations in blood pressure dependent activation of leg muscles during standing following bed rest mimic those observed with ageing"],"prefix":"10.3389","volume":"16","author":[{"given":"Malcom","family":"Tremblay","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Da","family":"Xu","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ajay K.","family":"Verma","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Nandu","family":"Goswami","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Andrew P.","family":"Blaber","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1965","published-online":{"date-parts":[[2025,4,29]]},"reference":[{"key":"B1","doi-asserted-by":"publisher","first-page":"H1114","DOI":"10.1152\/ajpheart.00391.2012","article-title":"Sex differences in blood pressure control during 6\u00b0 head-down tilt bed rest","volume":"304","author":"Arzeno","year":"2013","journal-title":"Am. J. Physiol. Heart Circ. Physiol."},{"key":"B2","doi-asserted-by":"publisher","first-page":"1061","DOI":"10.3389\/FPHYS.2019.01061","article-title":"Effects of prolonged head-down bed rest on cardiac and vascular baroreceptor modulation and orthostatic tolerance in healthy individuals","volume":"10","author":"Barbic","year":"2019","journal-title":"Front. Physiol."},{"key":"B3","doi-asserted-by":"publisher","first-page":"S21","DOI":"10.1016\/j.resp.2009.04.007","article-title":"Cardio-postural deconditioning: a model for post-flight orthostatic intolerance","volume":"1","author":"Blaber","year":"2009","journal-title":"Respir. Physiol. Neurobiol. Suppl."},{"key":"B4","doi-asserted-by":"publisher","first-page":"H1682","DOI":"10.1152\/ajpheart.1995.268.4.H1682","article-title":"Methodology of spontaneous baroreflex relationship assessed by surrogate data analysis","volume":"268","author":"Blaber","year":"1995","journal-title":"Am. J. Physiol."},{"key":"B40","doi-asserted-by":"publisher","first-page":"1909","DOI":"10.1007\/S00421-012-2539-X","article-title":"Cerebrovascular autoregulation: lessons learned from spaceflight research","volume":"113","author":"Blaber","year":"2013","journal-title":"Eur. J. Appl. Physiol."},{"key":"B5","doi-asserted-by":"publisher","first-page":"7","DOI":"10.1152\/jappl.1996.81.1.7","article-title":"Orthostatic intolerance after spaceflight","volume":"81","author":"Buckey","year":"1996","journal-title":"J. Appl. Physiol."},{"key":"B6","doi-asserted-by":"publisher","first-page":"R1909","DOI":"10.1152\/ajpregu.1998.275.6.R1909","article-title":"Gender differences in autonomic functions associated with blood pressure regulation","volume":"275","author":"Convertino","year":"1998","journal-title":"Am. J. Physiol."},{"key":"B7","doi-asserted-by":"publisher","first-page":"1458","DOI":"10.1152\/jappl.1990.68.4.1458","article-title":"Head-down bed rest impairs vagal baroreflex responses and provokes orthostatic hypotension","volume":"68","author":"Convertino","year":"1990","journal-title":"J. Appl. Physiol. (1985)"},{"key":"B8","doi-asserted-by":"publisher","first-page":"633987","DOI":"10.3389\/FNUT.2021.633987","article-title":"The aging muscle in experimental bed rest: a systematic review and meta-analysis","volume":"8","author":"Di Girolamo","year":"2021","journal-title":"Front. Nutr."},{"key":"B9","doi-asserted-by":"publisher","first-page":"2307","DOI":"10.1161\/01.STR.31.10.2307","article-title":"Orthostatic hypotension as a risk factor for stroke: the atherosclerosis risk in communities (ARIC) study, 1987-1996","volume":"31","author":"Eigenbrodt","year":"2000","journal-title":"Stroke"},{"key":"B10","doi-asserted-by":"publisher","first-page":"132","DOI":"10.1186\/1475-925X-12-132","article-title":"Statistical validation of wavelet transform coherence method to assess the transfer of calf muscle activation to blood pressure during quiet standing","volume":"12","author":"Garg","year":"2013","journal-title":"Biomed. Eng. Online"},{"key":"B11","doi-asserted-by":"publisher","first-page":"H259","DOI":"10.1152\/ajpheart.00171.2014","article-title":"Physiological interdependence of the cardiovascular and postural control systems under orthostatic stress","volume":"307","author":"Garg","year":"2014","journal-title":"Am. J. Physiol. Heart Circ. Physiol."},{"key":"B12","doi-asserted-by":"publisher","first-page":"603","DOI":"10.3389\/fphys.2017.00603","article-title":"Falls and fall-prevention in older persons: geriatrics meets spaceflight","volume":"8","author":"Goswami","year":"2017","journal-title":"Front. Physiol."},{"key":"B41","doi-asserted-by":"publisher","first-page":"453","DOI":"10.2147\/CIA.S76028","article-title":"Effect of computerized cognitive training with virtual spatial navigation task during bed rest immobilization and recovery on vascular function: a pilot study","volume":"10","author":"Goswami","year":"2015","journal-title":"Clin. Interv. Aging."},{"key":"B13","doi-asserted-by":"publisher","first-page":"803","DOI":"10.3389\/fphys.2017.00803","article-title":"Orthostatic intolerance in older persons: etiology and countermeasures","volume":"8","author":"Goswami","year":"2017","journal-title":"Front. Physiol."},{"key":"B14","doi-asserted-by":"publisher","first-page":"569","DOI":"10.1016\/j.physbeh.2012.02.022","article-title":"Delaying orthostatic syncope with mental challenge: a pilot study","volume":"106","author":"Goswami","year":"","journal-title":"Physiol. Behav."},{"key":"B15","doi-asserted-by":"publisher","first-page":"111","DOI":"10.1016\/j.pss.2012.07.030","article-title":"Using the Moon as a high-fidelity analogue environment to study biological and behavioral effects of long-duration space exploration","volume":"74","author":"Goswami","year":"","journal-title":"Planet Space Sci."},{"key":"B16","doi-asserted-by":"publisher","first-page":"688","DOI":"10.1016\/J.ACTAASTRO.2008.11.002","article-title":"Hemodynamic and neurohormonal responses to extreme orthostatic stress in physically fit young adults","volume":"64","author":"Grasser","year":"2009","journal-title":"Acta Astronaut."},{"key":"B17","doi-asserted-by":"publisher","first-page":"561","DOI":"10.5194\/npg-11-561-2004","article-title":"Application of the cross wavelet transform and wavelet coherence to geophysical time series","volume":"11","author":"Grinsted","year":"2004","journal-title":"Nonlinear Process Geophys"},{"key":"B18","doi-asserted-by":"publisher","first-page":"325","DOI":"10.3233\/VES-210016","article-title":"Long-duration head down bed rest as an analog of microgravity: effects on the static perception of upright","volume":"2","author":"Harris","year":"2022","journal-title":"J. Vestib. Res."},{"key":"B19","volume-title":"European recommendations for surface ElectroMyoGraphy results of the SENIAM project","author":"Hermens","year":"1999"},{"key":"B20","doi-asserted-by":"publisher","first-page":"1180","DOI":"10.1111\/j.1365-2362.2011.02523.x","article-title":"Hormonal and plasma volume changes after presyncope","volume":"41","author":"Hinghofer-Szalkay","year":"2011","journal-title":"Eur. J. Clin. Invest"},{"key":"B21","doi-asserted-by":"publisher","first-page":"367","DOI":"10.1161\/01.res.73.2.367","article-title":"Relative contributions of cardiopulmonary and sinoaortic baroreflexes in causing sympathetic activation in the human skeletal muscle circulation during orthostatic stress","volume":"73","author":"Jacobsen","year":"1993","journal-title":"Circ. Res."},{"key":"B22","doi-asserted-by":"publisher","first-page":"H1158","DOI":"10.1152\/AJPHEART.00965.2002","article-title":"Pathophysiology of orthostatic hypotension after bed rest: paradoxical sympathetic withdrawal","volume":"285","author":"Kamiya","year":"2003","journal-title":"Am. J. Physiol. Heart Circ. Physiol."},{"key":"B23","doi-asserted-by":"publisher","first-page":"1930","DOI":"10.1152\/jappl.1995.79.6.1930","article-title":"Venous mechanics of contracting gastrocnemius muscle and the muscle pump theory","volume":"79","author":"Magder","year":"1995","journal-title":"J. Appl. Physiol. (1985)"},{"key":"B24","first-page":"8","article-title":"The role of lower leg muscle activity in blood pressure maintenance of older adults","volume":"60","author":"Masterson","year":"2006","journal-title":"Clin. Kinesiol."},{"key":"B25","doi-asserted-by":"publisher","first-page":"H1486","DOI":"10.1152\/ajpheart.00740.2003","article-title":"Mechanisms of postspaceflight orthostatic hypotension: low alpha1-adrenergic receptor responses before flight and central autonomic dysregulation postflight","volume":"286","author":"Meck","year":"2004","journal-title":"Am. J. Physiol. Heart Circ. Physiol."},{"key":"B26","doi-asserted-by":"publisher","first-page":"230","DOI":"10.1109\/TBME.1985.325532","article-title":"A real-time QRS detection algorithm","volume":"32","author":"Pan","year":"1985","journal-title":"IEEE Trans. Biomed. Eng."},{"key":"B27","doi-asserted-by":"publisher","first-page":"848","DOI":"10.1016\/J.JACC.2015.06.1084","article-title":"Orthostatic hypotension: epidemiology, prognosis, and treatment","volume":"66","author":"Ricci","year":"2015","journal-title":"J. Am. Coll. Cardiol."},{"key":"B28","doi-asserted-by":"crossref","DOI":"10.1093\/oso\/9780195073621.001.0001","volume-title":"Human cardiovascular control","author":"Rowell","year":"1993"},{"key":"B29","doi-asserted-by":"publisher","first-page":"183","DOI":"10.1007\/BF01818960","article-title":"Gender related differences in the cardiovascular responses to upright tilt in normal subjects","volume":"2","author":"Schondorf","year":"1992","journal-title":"Clin. Auton. Res."},{"key":"B30","doi-asserted-by":"publisher","first-page":"1211774","DOI":"10.3389\/FCVM.2023.1211774","article-title":"Association of gender with cardiovascular and autonomic responses to central hypovolemia","volume":"10","author":"Shankhwar","year":"2023","journal-title":"Front. Cardiovasc Med."},{"key":"B31","doi-asserted-by":"publisher","first-page":"1","DOI":"10.1111\/j.1469-7793.1999.0001o.x","article-title":"Pathophysiological basis of orthostatic hypotension in autonomic failure","author":"Smit","year":"1999","journal-title":"J. Physiol."},{"key":"B32","doi-asserted-by":"publisher","first-page":"496","DOI":"10.1126\/science.1227079","article-title":"Detecting causality in complex ecosystems","volume":"338","author":"Sugihara","year":"2012","journal-title":"Science"},{"key":"B33","doi-asserted-by":"publisher","first-page":"553","DOI":"10.1042\/cs0870553","article-title":"Effects of leg muscle pumping and tensing on orthostatic arterial pressure: a study in normal subjects and patients with autonomic failure","volume":"87","author":"Ten Harkel","year":"1994","journal-title":"Clin. Sci. (Lond)"},{"key":"B34","doi-asserted-by":"publisher","first-page":"584","DOI":"10.1152\/japplphysiol.00738.2004","article-title":"Hemodynamic effects of leg crossing and skeletal muscle tensing during free standing in patients with vasovagal syncope","volume":"98","author":"van Dijk","year":"2005","journal-title":"J. Appl. Physiol. (1985)"},{"key":"B35","doi-asserted-by":"publisher","first-page":"45301","DOI":"10.1038\/srep45301","article-title":"Skeletal muscle pump drives control of cardiovascular and postural systems","volume":"7","author":"Verma","year":"2017","journal-title":"Sci. Rep."},{"key":"B36","doi-asserted-by":"publisher","first-page":"845","DOI":"10.3389\/fphys.2019.00845","article-title":"Effect of aging on muscle-pump baroreflex of individual leg muscles during standing","volume":"10","author":"Verma","year":"2019","journal-title":"Front. Physiol."},{"key":"B37","doi-asserted-by":"publisher","first-page":"1592","DOI":"10.1172\/JCI112142","article-title":"Interaction of cardiopulmonary and carotid baroreflex control of vascular resistance in humans","volume":"76","author":"Victor","year":"1985","journal-title":"J. Clin. Invest"},{"key":"B38","doi-asserted-by":"publisher","first-page":"12042","DOI":"10.1038\/s41598-020-68962-8","article-title":"Cardio-postural interactions and muscle-pump baroreflex are severely impacted by 60-day bedrest immobilization","volume":"10","author":"Xu","year":"2020","journal-title":"Sci. Rep."},{"key":"B39","doi-asserted-by":"publisher","first-page":"H568","DOI":"10.1152\/ajpheart.00836.2016","article-title":"Significant role of the cardiopostural interaction in blood pressure regulation during standing","volume":"313","author":"Xu","year":"2017","journal-title":"Am. J. Physiol. Heart Circ. Physiol."}],"container-title":["Frontiers in Physiology"],"original-title":[],"link":[{"URL":"https:\/\/www.frontiersin.org\/articles\/10.3389\/fphys.2025.1426648\/full","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,4,29]],"date-time":"2025-04-29T04:10:40Z","timestamp":1745899840000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.frontiersin.org\/articles\/10.3389\/fphys.2025.1426648\/full"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2025,4,29]]},"references-count":41,"alternative-id":["10.3389\/fphys.2025.1426648"],"URL":"https:\/\/doi.org\/10.3389\/fphys.2025.1426648","relation":{},"ISSN":["1664-042X"],"issn-type":[{"value":"1664-042X","type":"electronic"}],"subject":[],"published":{"date-parts":[[2025,4,29]]},"article-number":"1426648"}}