Fig 6. Slope of the fitted curves (${\text{log}\dot{\text{V}}}_{\text{E}}$ against ${\dot{\text{V}}\text{O}}_2$) from Fig 4(b) plotted against the total energy transfer during the test.

We find a relatively poor characterisation of the variance between performances. (b) By instead plotting the oxygen consumption at a fixed rate of breathing, we better capture differences in performance.