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Effects of Heavy-Intensity Priming Exercise on Pulmonary Oxygen Uptake Kinetics and Muscle Oxygenation in Heart Failure with Preserved Ejection Fraction.

Am J Physiol Regul Integr Comp Physiol. 2019 Jan 02;:

Authors: Boyes NG, Eckstein J, Pylypchuk S, Marciniuk D, Butcher SJ, Lahti DS, Dewa DMK, Haykowsky MJ, Wells CR, Tomczak CR

Abstract
Exercise intolerance is a hallmark feature in heart failure with preserved ejection fraction (HFpEF). Prior heavy exercise (“priming exercise”) speeds pulmonary oxygen uptake (V̇O2p)kinetics in older adults through increased muscle oxygen delivery and/or alterations in mitochondrial metabolic activity. We tested the hypothesis that priming exercise would speed V̇O2pon-kinetics in HFpEF patients due to acute improvements in muscle oxygen delivery. Seven HFpEF patients performed 3 bouts of 2 exercise transitions: MOD1, rest to 4-min moderate-intensity cycling; and MOD2, MOD1 preceded by heavy-intensity cycling. V̇O2p, heart rate (HR), total peripheral resistance (TPR), and vastus lateralis tissue oxygenation (TOI, near-infrared spectroscopy) were measured, interpolated, time-aligned, and averaged. V̇O2p and HR were monoexponentially curve-fitted. TPR and TOI levels were analyzed as repeated measures between pre-transition baseline, minimum value, and steady-state. Significance was P<0.05.tV̇O2p(MOD1 49±16 s) was significantly faster after priming (41±14 s; P=0.002) and the effective HR twas slower following priming (41±27 vs. 51±32 s; P=0.025). TPR in both conditions decreased from baseline to minimum TPR ( P<0.001), increased from minimum to steady-state ( P=0.041) but remained below baseline throughout ( P=0.001). Priming increased baseline ( P=0.003) and minimum TOI ( P=0.002) and decreased the TOI muscle deoxygenation overshoot ( P=0.041). Priming may speed the slow V̇O2p on-kinetics in HFpEF and increase muscle oxygen delivery (TOI) at the onset of and throughout exercise. Microvascular muscle oxygen delivery may limit exercise tolerance in HFpEF.

PMID: 30601707 [PubMed – as supplied by publisher]

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