I like to use this workout during the season to prepare for races sprint or Olympic-distance in particular. Perceived exertion on the five-minute intervals should be at or just above Olympic-distance race pace. The 30-second hard efforts are all-out efforts.
10 min including 4×30 sec high-cadence fast pedaling
4×5 min at HR Zone 4 with 3 min easy recovery 5 min at HR Zone 2 10×30 sec hard/30 sec easy recovery
Cool-down 5 min easy pedal