I think this might answer your question, SOC:
Chris Snell stressed that the Workwell Foundation remains committed to the repeat-maximal approach. First, VT can't be measured on the fly so they wouldn't know when to stop the test. And perhaps more importantly, the post-exertional effect appears to differ by patient, with some showing a greater effect on peak measures and others at VT. Dr Snell suggested that varying post-exertional responses may well reflect different underlying pathologies.
My confusion here may stem from my lack of expert knowledge about exercise testing, so someone correct me if I'm wrong....
I think the anaerobic threshold (AT) and the ventilatory threshold (VT) are essentially different names for the same point in exercise. There are some subtle differences, but they are generally used interchangeably. It is the point where the respiratory exchange ratio (RER) =1. In other words, VCO2/VO2 =1. This is easily, even routinely, measured in exercise testing. That's one of the reasons we wear that blasted mask. There's nothing difficult about measuring it on the fly as far as I can see, so Chris Snell must be talking about something else.
Blood lactate threshold (LT) is (I think) a more accurate way to find a person's AT. I can see how that might be difficult to measure on the fly. But Dr Snell is speaking specifically about the VT which, as I understand it, is
defined as a measure of respiratory gases, not blood or other measures.
So I don't yet understand what Dr Snell is saying about the difficulty of measuring VT on the fly and knowing when to stop.
I do understand his concern that some patients may show abnormalities at VT, while others show abnormalities on peak measures. This should definitely be taken into consideration, especially when trying to tease out different underlying pathologies.
All that said, if the work load at VT (VTWL or ATWL) is the measure that plummeted severely on second day testing, wouldn't it work as an objective measure for treatment studies? Stopping at (or just past) VT should still show the second day exercise capability crash, but would be significantly less risky for patients.
What am I missing here?