I was looking up polarised training to see if it had been done with a threshold day instead of a VO2 day, though yes I do get that that would be a bit of a contradiction of the term polarised.
Still I want to know if it can be done and what the improvements would be, what the workload and intervals might look like etc.
Saw this swimming study testing the models using zones 1 to 3. Anyone know what those 3 zones are for swimmers? Not up for reading all that on my phone