Figure 4

Simulated dynamic responses of oxygen uptake and carbon dioxide release during a 10-min moderate-intensity exercise bout (WR = 65W) of a sedentary individual. Positive values correspond to O₂ uptake (VO₂ = Q(C_a,O2 - σ_O2C_c,O2)) while negative values correspond to CO₂ release (VCO₂ = Q(C_a,CO2 - σ_CO2C_c,CO2)) from skeletal muscle. The time constant of O₂ uptake (τ_VO2) is about 0.5 min and that of CO₂ release (τ_VCO2) is about 0.6 min. The respiratory quotient (RQ = VCO₂/VO₂) increases from 0.785 at rest to 0.832 during exercise.