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Muscle substrate utilization from alveolar gas exchange in trained cyclists
- Source :
- European journal of applied physiology and occupational physiology. 72(4)
- Publication Year :
- 1996
-
Abstract
- The respiratory exchange ratio (R) during steady-state exercise is equivalent to whole-body respiratory quotient (RQ), but does not represent muscle metabolism alone. If steady-state values of carbon dioxide production (\(\dot VCO_2\)) and oxygen uptake (\(\dot VO_2\)) are plotted for different work rates, the slope of the line fitting these points should estimate muscle RQ. Twelve cyclists randomly performed five 8-min, constant work rate tests of 40, 80,120,160 and 200 W. Whole-bodyR, averaged over the final 2 min of each exercise bout, increased with increasing work rate. When\(\dot VCO_2\) was plotted as a function of\(\dot VO_2\), the regression lines through the five points displayed excellent linearity, had negative γ-intercepts, and a slope of 0.915 (0.043) [mean (SD)], which was greater than the whole-bodyR at any individual work rate [range 0.793 (0.027) at 40 W to 0.875 (0.037) at 200 W]. This slope was comparable to the lower slope of the\(\dot VCO_2\) versus\(\dot VO_2\) plot of an increasing work rate (ramp) protocol [0.908 (0.054)]. We conclude that, during mild and moderate exercise of relatively short duration, contracting muscle has a high and constant RQ, indicating that carbohydrate is the predominant metabolic substrate. WholebodyR does not accurately reflect muscle substrate utilization and probably underestimates muscle RQ at a given work rate.
- Subjects :
- Adult
Physiology
Analytical chemistry
Physical exercise
Work rate
Oxygen Consumption
Heart Rate
Physiology (medical)
Respiration
medicine
Ventilation-Perfusion Ratio
Humans
Orthopedics and Sports Medicine
Respiratory system
Muscle, Skeletal
Respiratory exchange ratio
Exercise
Chemistry
Pulmonary Gas Exchange
Public Health, Environmental and Occupational Health
Calorimetry, Indirect
General Medicine
Gas exchange
Anatomy
Carbon Dioxide
Bicycling
Respiratory quotient
medicine.symptom
Muscle contraction
Subjects
Details
- ISSN :
- 03015548
- Volume :
- 72
- Issue :
- 4
- Database :
- OpenAIRE
- Journal :
- European journal of applied physiology and occupational physiology
- Accession number :
- edsair.doi.dedup.....4ccfdec81b2120226c9522f9f4140799