title: Sex differences in the cardiovascular consequences of the inspiratory muscle metaboreflex.
abstract: It is currently unknown whether sex differences exist in the cardiovascular consequences of the inspiratory muscle metaboreflex. We hypothesized that the activation of the inspiratory muscle metaboreflex will lead to less of an increase in mean arterial pressure (MAP) and limb vascular resistance (LVR) and less of a decrease in limb blood flow (Q̇L) in women compared with men. Twenty healthy men (n = 10, 23 ± 2 yr) and women (n = 10, 22 ± 3 yr) were recruited for this study. Subjects performed inspiratory resistive breathing tasks (IRBTs) at 2% or 65% of their maximal inspiratory mouth pressure (PIMAX). During the IRBTs, the breathing frequency was 20 breaths/min with a 50% duty cycle. At rest and during the IRBTs, MAP was measured via automated oscillometry, Q̇L was measured via Doppler ultrasound, and LVR was calculated. EMG was recorded on the leg to ensure no muscle contraction occurred. The 65% IRBT led to attenuated increases (P < 0.01) from baseline in women compared with men for MAP (W: 7.3 ± 2.0 mmHg; M: 11.1 ± 5.0 mmHg) and LVR (W: 17.7% ± 14.0%; M: 47.9 ± 21.0%), as well as less of a decrease (P < 0.01) in Q̇L (W: -7.5 ± 9.9%; M: -23.3 ± 10.2%). These sex differences in MAP, Q̇L, and LVR were still present in a subset of subjects matched for PIMAX The 2% IRBT resulted in no significant changes in MAP, Q̇L, or LVR across time or between men and women. These data indicate premenopausal women exhibit an attenuated inspiratory muscle metaboreflex compared with age-matched men.
authors.affiliation: Department of Kinesiology, Kansas State University, Manhattan, Kansas smith424@ksu.edu.
authors.forename: Joshua R
authors.initials: JR
authors.lastname: Smith
authors.affiliation: Department of Kinesiology, Kansas State University, Manhattan, Kansas.
authors.forename: Ryan M
authors.identifier: 0000-0003-4803-9054
authors.initials: RM
authors.lastname: Broxterman
authors.affiliation: Department of Kinesiology, Kansas State University, Manhattan, Kansas.
authors.forename: Shane M
authors.initials: SM
authors.lastname: Hammer
authors.affiliation: Department of Kinesiology, Kansas State University, Manhattan, Kansas.
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Alexander
authors.affiliation: Department of Kinesiology, Kansas State University, Manhattan, Kansas.
authors.forename: Kaylin D
authors.initials: KD
authors.lastname: Didier
authors.affiliation: Department of Kinesiology, Kansas State University, Manhattan, Kansas.
authors.forename: Stephanie P
authors.identifier: 0000-0002-7388-2214
authors.initials: SP
authors.lastname: Kurti
authors.affiliation: Department of Kinesiology, Kansas State University, Manhattan, Kansas.
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Barstow
authors.affiliation: Department of Kinesiology, Kansas State University, Manhattan, Kansas.
authors.forename: Craig A
authors.initials: CA
authors.lastname: Harms
mesh_terms: D000328:Adult; D001783:Blood Flow Velocity / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology*; D004734:Energy Metabolism; D005260:Female; D006801:Humans; D001239:Inhalation / Q000502:physiology*; D007866:Leg / Q000098:blood supply / Q000502:physiology; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology*; D012018:Reflex; D012132:Respiratory Muscles / Q000502:physiology*; D012727:Sex Characteristics; D013564:Sympathetic Nervous System / Q000502:physiology; D014655:Vascular Resistance / Q000502:physiology*
keywords: blood pressure; limb vascular resistance; metaboreflex; sex differences