Bike Sessions: Long HIIIT vs VT2

General
1

I may be missing something here, but the differences and naming for these two sessions doesn’t make a lot of sense to me.

  • Long Interval HIIT: 5’ blocks @ Z4 w/ 3’ recoveries Z1
  • VT2: 4’ blocks @ Z4 w/ 2’ recoveries Z2

These are very similar. The same intensity (zone) is used for both, but the threshold (VT2) session allows for less recovery and that recovery is done at a higher intensity. I guess I don’t understand why shorter intervals (2-3’) @ Z5 aren’t used for long interval HIIT alternatives?

Thanks!