1. |
Draw the line of identity on the V̇CO_{2} versus V̇O_{2} plot (Figure 1) and identify whether an inflection occurred. |

2. |
Identify the ventilatory threshold from the inflection on the V̇_{E} versus V̇CO_{2} plot (Figure 2) and eliminate this point as a threshold candidate on the V̇CO_{2} versus V̇O_{2} plot. |

3. |
Mark the lower slope (S1) on the V̇CO_{2} versus V̇O_{2} 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 V̇CO_{2} versus V̇O_{2} 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 V̇CO_{2} versus V̇O_{2} plot and identify V̇O_{2}θ (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 V̇O_{2}θ from the V̇CO_{2} versus V̇O_{2} plot was 2 or 3, verify V̇O_{2}θ through use of the ventilatory equivalents versus V̇O_{2} plot (Figure 3A) and the end tidal gas tensions versus V̇O_{2} plot (Figure 3B). |

8. |
For the ventilatory equivalents plot, identify the first systematic upward inflection of V̇_{E}/V̇O_{2} without a simultaneous increase in V̇_{E}/V̇CO_{2}. From this inflection point, drop a perpendicular line to the x-axis of this plot (V̇O_{2}) and identify V̇O_{2}θ to the nearest 10-50 mL·min^{-1}. |

| For the plot of end tidal gas tensions, identify the first systematic increase in P_{ET}CO_{2} without a simultaneous decrease in P_{ET}CO_{2}. From this inflection point, drop a perpendicular line to the x-axis of this plot (V̇O_{2}) and identify V̇O_{2}θ 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 V̇O_{2}θ from these plots. |