i've had it done like mcjimbo describes. an estimate of lactate threshold was derived at the point the #s indicated the change from burning "fat calories" to "carb calories." a coach i used to work with used them for evaluating athletes she coached at 1) beginning of training season; 2) post base period; 3) around planned peak; 4) post race season. i didnt find the information particularly useful. coach did. i also found the variance between tests to be too great to correlate, and the time between tests too long to provide information that was useful to me.

i think the on road or on trainer testing is more useful for establishing training zones. there are lots of methodologies for differing training and measuring of training methodologies.

i wouldnt say that performing the testing is a waste, but it has its limitations and i'm of the opinion that other methods provide better information.