This block can be used as progression from part 1, or on its own. It can be either HISS or HIIT, depends on work:rest ratio & intensity selected.
For HISS keep rest equal or short than work 1:1 – 5:1
For HIIT keep rest longer than work 1:2 – 1:5
NOTE: Add more rest from round 2 onwards to make keep HIIT