[rojeee]

I think you are right regarding lactate threshold but im not sure how they factor in running economy as it's difficult to calculate. You need an accurate VO2 measurement. I guess they use HR as a proxy but in practise I find HR isn't such a good measure of metabolic output for various reasons; hills, unrelated stressors, heat, aerobic decoupling, etc.

[iamacyborg]

No one except elite athletes are looking at running economy, there are far too many confounding variables.

[rojeee]

Well.. a crude estimate of relative running economy is pace/heart rate and tracking it over time. Seeing the number go upwards means your economy is increasing and vice versa.

A fair amount of people track this because it's a feature of pretty much every training/coaching app.