Long - 6 x 4000m with cadence change / 2 min easy
Ride six 4000 meter pieces. In each piece change the cadence every 1000m. The first 1000m @ 75 spm. Then 1000m @ 85 spm. 1000m @ 75, and 1000m @ 85. Ride for two minutes easily during the rest period.

Check this Concept2 workout on the ErgZone app: