Lactate : Lactate Threshold
LoadThe lactate threshold is the intensity at which lactate accumulates faster than it is cleared.
At low intensity (Z1/Z2), lactate is cleared as fast as it's produced. Past the first threshold (LT1, the lower boundary of Z3), it begins to accumulate slowly. At the second threshold (LT2, equivalent to FTP on the bike), accumulation accelerates and the effort can't be sustained long. Pushing LT1 upward through long Z2 sessions is the main goal of aerobic base training.
In TriPaced:
In TriPaced, intensity zones are computed from FTP (bike) and CSS (swim), which roughly correspond to LT2. Long Z2 sessions aim to push LT1 higher, building your aerobic base.
Source Faude, Kindermann & Meyer, 2009 : Lactate threshold concepts: how valid are they?