This is very tough set.A huge V02max set. During the flying 40s the 40s on can be as hard as you like without considering the efforts still to come. It is common to see power and speed drop through these efforts. They are a great way to build endurance and cycle economy.
HR may not be very sensitive to changes in effort throughout the efforts, so focus on RPE.
Keep this Steady. You should be able to eat and/or talk for the entire distance.
A rolling hilly route is best.
This session is an easy session that will allow recovery but develop your ability to change cadence and improve the nueromuscular co ordination of muscle groups at each cadence.
This session develop peak power and V02 max increasing aerobic capacity and neuro-muscular co-ordination.
This is a swim endurance set so keep early reps comfortable as finishing strongly is important.
If you cannot complete 3000 in 1hr do same sets but with 750m or extend time allowed.
2 ride @ zone2 or 6/10 rpe