Pulmonary and leg V̇O2 during submaximal exercise: Implications for muscular efficiency

D. C. Poole, G. A. Gaesser, M. C. Hogan, D. R. Knight, P. D. Wagner

Research output: Contribution to journalArticle

144 Scopus citations

Abstract

Insights into muscle energetics during exercise (e.g., muscular efficiency) are often inferred from measurements of pulmonary gas exchange. This procedure presupposes that changes of pulmonary O2 (V̇O2) associated with increases of external work reflect accurately the increased muscle V̇O2. The present investigation addressed this issue directly by making simultaneous determinations of pulmonary and leg V̇O2 over a range of work rates calculated to elicit 20-90% of maximum V̇O2 on the basis of prior incremental (25 or 30 W/min) cycle ergometry. V̇O2 for both legs was calculated as the product of twice one-leg blood flow (constant-infusion thermodilution) and arteriovenous O2 content difference across the leg. Measurements were made 3-5 min after each work rate imposition to avoid incorporation of the V̇O2 slow component above the lactate threshold. For all 17 subjects, the slope of pulmonary V̇O2 (9.9 ± 0.2 ml O2 · W-1 · min-1) was not different (P > 0.05) from that for leg V̇O2 (9.2 ± 0.6 ml O2 · W-1 · min-1). Estimation of 'delta' efficiency (i.e., delta work accomplished divided by delta energy expended, calculated from slope of V̇O2 vs. work rate and a caloric equivalent for O2 of 4.985 cal/ml) using pulmonary V̇O2 measurements (29.1 ± 0.6%) was likewise not significantly different (P > 0.05) from that made using leg V̇O2 measurements (33.7 ± 2.4%). These data suggest that the net V̇O2 cost of metabolic 'support' processes outside the exercising legs changes little over a relatively broad range of exercise intensities. Thus, under the conditions of this investigation, changes of V̇O2 measured from expired gas reflected closely those occurring within the exercising legs.

Original languageEnglish (US)
Pages (from-to)805-810
Number of pages6
JournalJournal of Applied Physiology
Volume72
Issue number2
DOIs
StatePublished - 1992

Keywords

  • 'delta' efficiency
  • cycle ergometry
  • leg blood flow
  • oxygen uptake kinetics
  • ventilation

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

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