One of the issues translating pro training to us mere mortals is how much room we have to work around that ‘high Zone 2,’ Aerobic Threshold-ish, BLa 1.3-1.8-ish target. This is illustrated well in San-Millan’s 2018 paper.
Take a look at the BLa to FATox curves in Pro athlete vs healthy individual
The Pro has far more room to play under her target intensity, if we’re estimating as ~1.5 mmol BLa. The healthy non-athlete has a much steeper lactate curve. And I would imagine most of us are somewhere in between these extremes.
In my opinion, the cost to us of going a few watts harder might mean our relative intensity is further off-target, than for the Pro. We have a much tighter range, and a steeper ‘cliff’ beyond which spending too much volume at too high intensity may diminish our returns. Not to mention fatigue resistance and response to duration (ie. a Pro will see less physiological drift over longer durations at the same relative intensity).
For that reason I think we’re better served by hedging lower for our low-intensity training, and not trying to push up on the limit of Zone 2/AeT/etc. Because it’s easier for us to go over, and the cost is higher if we do. Then add ‘glycolytic training’ (Tempo, SST, HIIT, etc.) as our high intensity sessions.
Another reason it might be better to hedge low if you don’t have access to regular testing?