Long - 6 x 4000m with cadence change / 2 min easy
Ride six 4000 meter pieces. In each piece change the rate every 1000m. The first 1000m @ 85 rpm. Then 1000m @ 95 rpm. 1000m @ 85 and 1000m @ 95. Ride for two minutes easily during the rest period.
Check this Concept2 workout on the ErgZone app: