Start 4min R18 at intensity of your 20min test split + 8 seconds, then for each rate change drop 1-2 seconds. As you get to R24 you should be around 1-3 seconds below your 20 min test split ).
This workout is a combination of aerobic endurance and aerobic power. One of the key points of doing this workout is to keep your splits consistent climbing up and down the rates.
Day 2) Erging
Warm up for 18min
1 x 5 min R28, 20min test split + 2seconds / rest 5 min
3 x 3 min R28-30, intensity: projected 2k+1 second / Rest 3 min (20min test split - 8-7 seconds )
Day 3) Practice on water
Plan A. If water is calm and we can row to 1000m, then we'll do 2 x 2000m Time Trial R26/28
Plan B. If there are some waves but we still can row to 750m, then 4 x 1500m (R18/R24/R26/R26)
Plan C. If there is 500m only to row, we still do pieces or Steady states, depending on the wind conditions.