Hi John,
UA sets aerobic threshold by lactate at 2mmol or 1mmol above baseline. So, in your case ~147 bpm.
> We use the widely accepted blood lactate concentration of 2mMol/L to define AeT. However, some literature suggests a concentration of as high as 2.5mMol/L, and one method defines AeT as the point where lactate rises 1mMol/L above the lowest reading obtained during the warm-up or while the athlete is resting. Just be consistent with the measurement and protocol you use. [1]
Not an expert, but from what I’ve read, there are many definitions of aerobic threshold. The first point of deflection in lactate is another, as suggested by your lab (~132 bpm at sample 3). In this case, they may also be referring to aerobic threshold as the floor of your Zone 2 (in a 5 zone model), which would be equivalent to Tempo in their training zones? Whichever, it’s an interesting mark in physiological change – lactate is increasing, suggesting fast twitch muscle fibers coming into play.
[1] https://uphillathlete.com/aerobic-training/blood-lactate-test-protocol-tips-and-tricks/