I received a comment on the Concept 2 UK Forum today in reference to my post on the lactate threshold.
The author said "I think your confusing LT with AT. Lactate threshold is commonly believed to be 2 mmol and AT is 4 mmol." and then included this example graph.
I admitted that I was in essence wrong, but also deliberatly trying to use language in common use. I would suggest that most people are familiar with the point around 4 mmol but few are familiar with the first point at 2 mmol. As such people have fallen into the habit of using lactate threshold and anaerobic threshold interchangably. I have always used the more descriptive term OBLA- onset of blood lactate accumulation for the 2 mmol point as it indicates the point of exercise intensity where lactate accumulates beyond its resting value. It in itself is a bit deceiving, because you won't see many real curves for athletes that fit this tidy description, with a horizontal lactate curve until it finally begins to rise at 2 mmol.
Peter Janssen in his very interesting book "Lactate Threshold Training" uses the terms very much interchangably (for example p.35 - "The anaerobic or lactate threshold corresponds to the..."). Although he mostly uses the term IAT (individual anaerobic treshold) and V4 to indicate the velocity at 4 mmol - fully admitting 4 mmol is not the IAT for everyone, but still a useful measure.
See book at Amazon.com
It is also interesting that many people also refer to the term MLSS - maximal lactate steady state. This would be the maximal steady state levek of lactate that can be maintained. In otherwords, during exercise while lactate levels rise, if a further increment in intensity is not made, then eventually that lactate level will level out and be maintained - the body's ability to clear the lactate is matched to the production. At some point - the MLSS - this does not happen and lactate continues to accumulate.
One interesting study presented in 1995 in rowers called Anaerobic threshold, individual anaerobic threshold, and maximal lactate steady state in rowing measured the MLSS, the AT4 (anaerobic threshold, by definition at 4 mmol) and the IAT - determined from the graph, not by definition at 4 mmol.
They found the IAT and AT4 to be almost the same (287 W vs. 287.1 W on average) but the MLSS was lower - at 255.1 W.
This fits with my brief experience testing naitonal team athletes. We were asked to extrpolate training zones based on the 4 mmol point. At the next session it was almost unanimously reported by the athletes that the wattages given for apparently steady state work had been far too high - presumably refelcting a lower MLSS in rowing.