In:
Journal of Applied Physiology, American Physiological Society, Vol. 103, No. 5 ( 2007-11), p. 1722-1727
Abstract:
We examined peak and reserve cardiovascular function and skeletal muscle oxygenation during unilateral knee extension (ULKE) exercise in five heart transplant recipients (HTR, mean ± SE; age: 53 ± 3 years; years posttransplant: 6 ± 4) and five age- and body mass-matched healthy controls (CON). Pulmonary oxygen uptake (V̇o 2 p ), heart rate (HR), stroke volume (SV), cardiac output (Q̇), and skeletal muscle deoxygenation (HHb) kinetics were assessed during moderate-intensity ULKE exercise. Peak exercise and reserve V̇o 2 p , Q̇, and systemic arterial-venous oxygen difference (a-vO 2diff ) were 23–52% lower ( P 〈 0.05) in HTR. The reduced Q̇ and a-vO 2diff reserves were associated with lower HR and HHb reserves, respectively. The phase II V̇o 2 p time delay was greater (HTR: 38 ± 2 vs. CON: 25 ± 1 s, P 〈 0.05), while time constants for phase II V̇o 2 p (HTR: 54 ± 8 vs. CON: 31 ± 3 s), Q̇ (HTR: 66 ± 8 vs. CON: 28 ± 4 s), and HHb (HTR: 27 ± 5 vs. CON: 13 ± 3 s) were significantly slower in HTR. The HR half-time was slower in HTR (113 ± 21 s) vs. CON (21 ± 2 s, P 〈 0.05); however, no significant difference was found between groups for SV kinetics (HTR: 39 ± 8 s vs. CON 31 ± 6 s). The lower peak V̇o 2 p and prolonged V̇o 2 p kinetics in HTR were secondary to impairments in both cardiovascular and skeletal muscle function that result in reduced oxygen delivery and utilization by the active muscles.
Type of Medium:
Online Resource
ISSN:
8750-7587
,
1522-1601
DOI:
10.1152/japplphysiol.00725.2007
Language:
English
Publisher:
American Physiological Society
Publication Date:
2007
detail.hit.zdb_id:
1404365-8
SSG:
12
SSG:
31
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