On one hand, I think TSB is a useful metric and I do buy into the idea of what Joe Friel says regarding optimal training happening after about -10 TSB. I’ve been doing SSB1 HV these past few weeks and I’m not anticipating any changes. Partly it’s due to the fact that I had done SSB1HV and SSB2HV over the winter (followed by a week vacation in late Feb with a VO2 progression block done throughout March and April), so I’ve had a pretty decent base, and I started the block at 74 CTL and after Sunday’s workout I was at 81, so not a huge jump over 5 weeks. My TSB never went really deep and just after this past weekend of 2 big workouts did it go to -15. While I think I got the benefits of doing sweet spot in a lot of ways, the level of work really isn’t going to elicit any changes from an FTP standpoint.
But I also think that speaks to the fact that I was training a system that was pretty well developed and if I may have had different results if I had done similar TSS but with more demanding threshold/over-threshold work.