These are 4 blocks of 5 seated accelerations in a gear 1 to 2 sprockets higher than normal over 200 metres for 15-20sec.
Warm up for 15min, zone 2, then do 3min in zone 4 to open the legs up, 5min easy zone 1 and 2. Do the first block of 5 accelerations. Start at a moderate pace and then accelerate as hard as you can, seated, for 200 metres. Have 1min rests between accelerations and 15min between blocks.
Then warm down. Zone 2 between sprints and don’t worry what zone you do during sprints.
Change of pace is essential for road racing. These accelerations train you to change pace without wasting energy getting in and out of the saddle.