Long - 5 x 4000m cadence change / 2 min easy
Ride five 4000 meter pieces. In each piece change the cadence every 1000m. The first 1000m @ 75 rpm. Then 1000m @ 85 rpm, 1000m @ 75, 1000m @ 75, and 1000m @ 85. Ride for two minutes easily during the rest period.
Check this Concept2 workout on the ErgZone app: