| 1. |
Draw the line of identity on the V̇CO2 versus V̇O2 plot (Figure 1) and identify whether an inflection occurred. |
| 2. |
Identify the ventilatory threshold from the inflection on the V̇E versus V̇CO2 plot (Figure 2) and eliminate this point as a threshold candidate on the V̇CO2 versus V̇O2 plot. |
| 3. |
Mark the lower slope (S1) on the V̇CO2 versus V̇O2 plot which should lie below the line of identity. Note that some subjects might hyperventilate during this stage of the study whereupon the data will lie above the line of identity. These data should be discounted for the purposes of identifying the threshold. |
| 4. |
Mark the upper slope (S2) on the V̇CO2 versus V̇O2 plot and identify the point of intersection between S1 and S2 (This should lie below the line of identity). |
| 5. |
Drop a perpendicular line to the x-axis of the V̇CO2 versus V̇O2 plot and identify V̇O2θ (the metabolic threshold) to the nearest 10-50 mL·min-1. |
| 6. |
Assign a level of confidence to the threshold detection from this plot (1=confident; 2=fairly confident; 3=poorly confident). |
| 7. |
If confidence in choosing V̇O2θ from the V̇CO2 versus V̇O2 plot was 2 or 3, verify V̇O2θ through use of the ventilatory equivalents versus V̇O2 plot (Figure 3A) and the end tidal gas tensions versus V̇O2 plot (Figure 3B). |
| 8. |
For the ventilatory equivalents plot, identify the first systematic upward inflection of V̇E/V̇O2 without a simultaneous increase in V̇E/V̇CO2. From this inflection point, drop a perpendicular line to the x-axis of this plot (V̇O2) and identify V̇O2θ to the nearest 10-50 mL·min-1. |
|
For the plot of end tidal gas tensions, identify the first systematic increase in PETCO2 without a simultaneous decrease in PETCO2. From this inflection point, drop a perpendicular line to the x-axis of this plot (V̇O2) and identify V̇O2θ to the nearest 10-50 mL·min-1. |
| 9. |
Where the plots of ventilatory equivalents and end-tidal gas tensions can be plotted one above the other with identical x-axes, use a vertical cursor to select the threshold that best represents upward inflections on both plots (as described above). |
| 10. |
Assign confidence levels (1=confident; 2=fairly confident. 3=poorly confident) to section of V̇O2θ from these plots. |
