title: Cardiovascular consequences of the inspiratory muscle metaboreflex: effects of age and sex.
abstract: With inspiratory muscle metaboreflex activation, we hypothesized that, compared with their younger counterparts, older men and women would exhibit greater1) increases in mean arterial pressure (MAP) and limb vascular resistance (LVR) and2) decreases in limb blood flow (Q̇L) but3) no sex differences would be present in older adults. Sixteen young adults [8 young men (YM) and 8 young women (YW), 18-24 yr] and 16 older adults [8 older men (OM) and 8 older women (OW), 60-73 yr] performed inspiratory resistive breathing tasks (IRBTs) at 2% and 65% of their maximal inspiratory pressure. During the IRBTs, breathing frequency was 20 breaths/min with a 50% duty cycle. At baseline and during the IRBTs, MAP was measured via automated oscillometry, Q̇Lwas determined via Doppler ultrasound, and LVR was calculated. The 65% IRBT led to significantly greater increases in MAP in OW (15.9 ± 8.1 mmHg) compared with YW (6.9 ± 1.4 mmHg) but not (P> 0.05) between OM (12.3 ± 5.7 mmHg) and YM (10.8 ± 5.7 mmHg). OW (-20.2 ± 7.2%) had greater (P< 0.05) decreases in Q̇Lcompared with YW (-9.4 ± 10.2%), but no significant differences were present between OM (-22.8 ± 9.7%) and YM (-22.7 ± 11.3%) during the 65% IRBT. The 65% IRBT led to greater (P< 0.05) increases in LVR in OW (48.2 ± 25.5%) compared with YW (19.7 ± 15.0%), but no differences (P> 0.05) existed among OM (54.4 ± 17.8%) and YM (47.1 ± 23.3%). No significant differences were present in MAP, Q̇L, or LVR between OM and OW. These data suggest that OW exhibit a greater inspiratory muscle metaboreflex compared with YW, whereas no differences between OM and YM existed. Finally, sex differences in the inspiratory muscle metaboreflex are not present in older adults.NEW & NOTEWORTHYPremenopausal women exhibit an attenuated inspiratory muscle metaboreflex compared with young men; however, it is unknown whether these sex differences are present in older adults. Older women exhibited a greater inspiratory muscle metaboreflex compared with premenopausal women, whereas no differences were present between older and younger men.
authors.affiliation: Department of Kinesiology, Kansas State University, Manhattan, Kansas smith424@ksu.edu.
authors.forename: Joshua R
authors.identifier: http://orcid.org/0000-0002-3687-6261
authors.initials: JR
authors.lastname: Smith
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: Shane M
authors.initials: SM
authors.lastname: Hammer
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: http://orcid.org/0000-0003-4803-9054
authors.initials: SP
authors.lastname: Kurti
authors.affiliation: Department of Kinesiology, Kansas State University, Manhattan, Kansas.
authors.forename: Ryan M
authors.initials: RM
authors.lastname: Broxterman
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: D000293:Adolescent; D000328:Adult; D000368:Aged; D000375:Aging; D062186:Arterial Pressure; D002320:Cardiovascular Physiological Phenomena; D005121:Extremities / Q000098:blood supply; D005260:Female; D006801:Humans; D008168:Lung / Q000502:physiology; D008297:Male; D008875:Middle Aged; D012039:Regional Blood Flow / Q000502:physiology; D012132:Respiratory Muscles / Q000254:growth & development / Q000502:physiology*; D012727:Sex Characteristics; D014655:Vascular Resistance / Q000502:physiology; D055815:Young Adult
keywords: aging; blood pressure; limb vascular resistance; metaboreflex