Fig. 3.
The Fick principle curve depicts muscle O2 consumption (mVO2) as a function of convective O2 delivery (curved line) vs. venous partial pressure of O2 (Po2). Fick’s law of diffusion depicts mVO2 as a function of venous Po2, with the slope (straight line) representative of muscle O2 diffusive conductance. The intersection of these lines determines the mVO2 achieved. A: the transition from rest to 10 kg of rhythmic handgrip exercise was achieved by a greater increase in diffusive O2 conductance compared with convective O2 delivery. B: the increase in mVO2 from 10 to 19 kg was achieved by an increase in both convective O2 delivery and diffuse O2 conductance that resulted in a minimal change in venous Po2. C: the arterial (open bars) and venous (closed bars) O2 transport at rest and at the end of each respective exercise workload. O2 utilization (O2 Util.) was calculated as the differences between arterial and venous O2 transport, expressed in milliliters of O2 per minute. Data are reported as means ± SE; n = 8.