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Effect of Aging on the Inspiratory Muscle Metaboreflex
Author(s) -
Smith Joshua R,
Broxterman Ryan M,
Hammer Shane M,
Alexander Andrew M,
Didier Kaylin D,
Barstow Thomas J,
Kurti Stephanie P,
Harms Craig A
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.1289.6
Subject(s) - medicine , cardiology , blood pressure , blood flow , hemodynamics , anesthesia
Activation of the inspiratory muscle metaboreflex leads to increased sympathetic outflow, mean arterial pressure (MAP), limb vascular resistance (LVR), and decreased limb blood flow. With aging, the skeletal muscle metaboreflex has been reported to be attenuated, similar, or exaggerated compared to younger adults. However, it is not known if aging influences the inspiratory muscle metaboreflex. Purpose The purpose was to determine if aging influences the inspiratory muscle metaboreflex in healthy humans. We hypothesized that compared to younger adults, older adults would exhibit less of: 1) an increase in MAP and diastolic blood pressure (DBP), 2) a decrease in limb blood flow, and 3) an increase in LVR. Methods Sixteen healthy older (M:2/W:6; 65.3 ± 5.5 yrs) and young (M:2/W:6; 22.3 ± 2.9 yrs) adults were recruited for this study and visited the laboratory on three different occasions. All young women were tested during the early follicular phase of their menstrual cycle and all older women were post‐menopausal. On the first visit, subjects were familiarized with all procedures and measurements. The next two visits were randomized and subjects performed an inspiratory resistive breathing task (IRBT) at ~2% or ~70% of their maximal inspiratory mouth pressure (PImax) for 20 min. During the IRBTs, the breathing frequency was 20 breaths per min with a 0.5 duty cycle. At rest and during the IRBTs, blood pressure was measured via automated oscillometry, femoral artery blood flow (FABF) was measured via Doppler ultrasound, end tidal CO2 was continuously monitored, and LVR was calculated MAP divided by FABF. Surface EMGs were placed on the leg to ensure no muscle contraction occurred. Results During the 20 min at ~70%PImax, older adults had a greater (p<0.05) increase in MAP (O: 12.1 ± 4.1% vs. Y: 2.3 ± 4.1%), SBP (O: 16.1 ± 12.6% vs. Y: 5.7 ± 4.9%), and DBP (p=0.06) (O: 9.0 ± 10.6% vs. Y: 0.6 ± 5.2%) compared to young adults. No differences (p>0.05) were present in HR or FABF (O: −13.6 ± 12.0% vs. Y: −7.3 ± 7.3%) over the 20 min. However, older adults had a greater increase in LVR compared to young adults (O: 33.5 ± 19.9% vs. Y: 13.9 ± 12.3%). Conclusion These data suggest that aging leads to an exaggerated inspiratory muscle metaboreflex in healthy humans.