title: Cardiovascular responses to forearm muscle metaboreflex activation during hypercapnia in humans.
abstract: We characterized the cardiovascular responses to forearm muscle metaboreflex activation during hypercapnia. Ten healthy males participated under three experimental conditions: 1) hypercapnia (HCA, PetCO2 : +10 mmHg, by inhalation of a CO2-enriched gas mixture); 2) muscle metaboreflex activation (MMA, by 5 min of local circulatory occlusion after 1 min of 50% maximum voluntary contraction isometric handgrip under normocapnia); and 3) HCA+MMA. We measured mean arterial pressure (MAP), heart rate (HR), and cardiac output (CO); calculated stroke volume (SV), and total peripheral resistance (TPR); and evaluated myocardial oxygen consumption (MV̇o2) and cardiac work (CW) noninvasively. MAP increased in the three experimental conditions but HCA+MMA led to the highest MAP, CO, and HR. Moreover, HCA+MMA increased SV and was associated with the highest MV̇o2 and CW. HCA and MMA exhibited inhibitory interactions with MAP, HR, TPR, MV̇o2, and CW, increases of which were smaller during HCA+MMA than the sum of the increases during HCA and MMA alone (MAP: +28 ± 2 vs. +34 ± 2 mmHg, P < 0.001; HR: +15 ± 2 vs. +22 ± 3 bpm, P < 0.01; TPR: +1.1 ± 1.4 vs. +3.0 ± 1.5 mmHg·l·min(-1), P < 0.05; MV̇o2: +50.25 ± 4.74 vs. +59.48 ± 5.37 mmHg·min(-1)·10(-2), P < 0.01; CW: +59.10 ± 7.52 vs. +63.67 ± 7.71 ml mmHg·min(-1)·10(-4), P < 0.05). Oppositely, HCA and MMA interactions were linearly additive for CO (+2.3 ± 0.4 l/min) and SV (+13 ± 4 ml). We showed that muscle metaboreflex and hypercapnia interact in healthy humans, reducing vasoconstriction but enhancing SV.
authors.affiliation: Aix-Marseille University, MD, DS-ACI, UMR 2, Marseille, France; APHM, Hôpital Nord, Pôle cardiovasculaire et thoracique, Laboratoire de Physiologie Respiratoire-Explorations à l'Exercice, Marseille, France; Assistance Publique, Hôpitaux de Marseille, Hôpital Nord, Pôle cardiovasculaire et thoracique, Laboratoire de Physiologie Respiratoire-Explorations à l'Exercice, Marseille, France; Laboratory of Physiology-Circulation, Institute of Health and Sport Sciences, University of Tsukuba, Tsukuba, Japan; and Japan Society for the Promotion of Science, Tokyo, Japan stephane.delliaux@univ-amu.fr.
authors.forename: Stephane
authors.initials: S
authors.lastname: Delliaux
authors.affiliation: School of Business and Administration, Meiji University, Tokyo, Japan; Laboratory of Physiology-Circulation, Institute of Health and Sport Sciences, University of Tsukuba, Tsukuba, Japan; and.
authors.forename: Masashi
authors.initials: M
authors.lastname: Ichinose
authors.affiliation: Laboratory of Physiology-Circulation, Institute of Health and Sport Sciences, University of Tsukuba, Tsukuba, Japan; and.
authors.forename: Kazuhito
authors.initials: K
authors.lastname: Watanabe
authors.affiliation: Laboratory of Physiology-Circulation, Institute of Health and Sport Sciences, University of Tsukuba, Tsukuba, Japan; and Japan Society for the Promotion of Science, Tokyo, Japan.
authors.forename: Naoto
authors.initials: N
authors.lastname: Fujii
authors.affiliation: Laboratory of Physiology-Circulation, Institute of Health and Sport Sciences, University of Tsukuba, Tsukuba, Japan; and.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Nishiyasu
mesh_terms: D000328:Adult; D062186:Arterial Pressure; D002628:Chemoreceptor Cells / Q000378:metabolism*; D004734:Energy Metabolism; D005542:Forearm; D006339:Heart Rate; D006439:Hemodynamics; D006801:Humans; D006935:Hypercapnia / Q000378:metabolism / Q000503:physiopathology*; D007537:Isometric Contraction; D008297:Male; D018482:Muscle, Skeletal / Q000294:innervation* / Q000378:metabolism; D012018:Reflex; D013318:Stroke Volume; D013997:Time Factors; D014655:Vascular Resistance; D014661:Vasoconstriction; D055815:Young Adult
keywords: hypercapnia; hypertension; muscle metaboreflex; myocardial oxygen consumption; stroke volume