Metabolic control of cardiac output response to exercise in McArdle's disease

S. F. Lewis, R. G. Haller, J. D. Cook, C. G. Blomqvist

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35 Scopus citations


During dynamic exercise cardiac output (Q̇) normally increases ~5 liters per liter of increase in O2 uptake (V̇(O2)) (i.e., ΔQ̇/ΔV̇(O2) ≃5), indicative of a tight coupling between systemic O2 transport and utilization. We studied four patients with muscle phosphorylase deficiency (McArdle's disease) in whom Q̇ was normal at rest, but ΔQ̇/ΔV̇(O2) was 14.1 ± 1.3 during bicycle exercise. Procedures designed to alter the availability of substrates were employed to test the hypothesis that the increased ΔQ̇/ΔVΔ(O2) is linked to the abnormal metabolic state of skeletal muscle. Fasting plus prolonged moderate exercise was used to increase the availability of plasma free fatty acid (FFA) and resulted in a normalization of ΔQ̇/ΔV̇(O2) (5.3 ± 0.4). Hyperglycemia (70% above control levels) partially normalized ΔQ̇/ΔV̇(O2). Nicotinic acid lowered plasma FFA concentration and dramatically increased ΔQ̇/ΔV̇(O2) (4.6 to 13.7) when administered after fasting plus prolonged exercise in one patient. Glucose infusion after nicotinic acid administration markedly lowered ΔQ̇/ΔV̇(O2). The results support the hypothesis and suggest that the metabolic state of skeletal muscle, possibly via activation of muscle afferents, participates in the regulation of systemic O2 transport.

Original languageEnglish (US)
Pages (from-to)1749-1753
Number of pages5
JournalJournal of Applied Physiology Respiratory Environmental and Exercise Physiology
Issue number6
StatePublished - 1984

ASJC Scopus subject areas

  • Physiology
  • Endocrinology


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