Is XEP meant to imply an average power of its magnitude could, in fact, be held for the period it’s calculated for? For me, XEP is usually 8 to 10 watts higher than normalized power (NP) for shorter (5 to 20 minutes) efforts, and when I look at NP I usually think it would be a stretch to hold that as average power for whatever the time period, let alone 10 watts higher.

XEP, unlike NP, is only used for relative effort approximation. (NP is used for this and for stress score calculations). We don’t make any claims of how long you can sustain XEP since it is an approximation as it’s attempting to describe 3 dimensions of relative power in just one dimension. Reviewing our blog on it (Fitness Prediction and Potential) you’ll see that it approximates a normalizing method but only under certain conditions.

Thanks, that makes complete sense (to my body).