The main set for this session was given to my sister one day from our masters coach. At the time in her season she hadn’t any anaerobic work done and she didn’t fancy doing the nausiator, so he gave her this. I liked it and continue to use it with a slight tweak because it feels a bit easier than my other go to sessions. I’m not sure if it is actually easier or if it’s all just in my head. I normally swim this early in the season to ease myself back into this kind of training, or if I’m doing more than one anaerobic session per week then I might use this for one of them. To make the session a bit more advanced try doing the 50s Fc off 1:00 and do 2×50 Bc per round. Once in the main set there is no stopping, no pause between the repetitions.