I am still using HR to define my zones. With daylight at a premium, I am looking at "bang for the buck" solutions to occasionally spice up the drudgery of Z1-Z2 base. In looking at the calculations for both "tempo" and "sweet spot" it seems they are quite similar (Both hovering at about 90% of LTHR). It appears that the major difference is that SST takes into account training load metrics (as derived from training with power) while tempo does not.

Am I correct in this thinking? and if not, please educate me. TIA

Um. If you're training with power, tempo will take into account training load metrics as well.

Mid to upper end of tempo is what you're thinking of. Hit it up!

I'd say tempo is a training intensity, sweet spot is a concept. The idea is that there is a trade off between increasing intensity and the training volume you can perform. Higher intensity gives a higher training load per time but over a shorter time. A lower intensity allows more training but with less benefit per time. The sweet spot is the area where the product of intensity and training time provides the greatest improvement. Of course, this depends on the individual and is also a function of available training time. Generally, sweet spot is applied to aerobic fitness, and specificity should not be ignored.

Thanks. That is exactly what I needed clarification on.