Some of the studies cited in the paper you linked to above are very clear that they are using the Hunter Allen protocol (5 minute all out effort followed by 20 minute all out effort), whereas some of them appear to be quite ambiguous about the protocol used.
Here’s are a couple of examples of the protocols:
The only one I read in any great detail which did not use the Hunter Allen test found there was very poor correlation between MMP20 and MLSS.
Mike