Cardiovascular consequences of the inspiratory muscle metaboreflex: Effects of age and sex

With inspiratory muscle metaboreflex activation, we hypothesized that, compared with their younger counterparts, older men and women would exhibit greater 1 increases in mean arterial pressure (MAP) and limb vascular resistance (LVR) and 2) decreases in limb blood flow (˙L) but 3) 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, Q_L was 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 ˙L greater (P< 0.05) decreases in Q_L compared 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, Q_L, 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 & NOTEWORTHY Premenopausal 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.