Hi @sir_james.p and all,
As you have noticed, there have been some adjustments made to many of the Sufferfest sessions in SYSTM. There are 24 SUF workouts that were not changed in any way, but 23 have been adjusted (not including any mashups in either of those counts).
The primary reason that I personally made the adjustments to the 23 workouts was that our sports science team reviewed all of our workouts from various physiological models (with heavy computational lifting from @Coach.Mac.C including W’ analysis of anaerobic capacity, predicted oxygen consumption and oxygen deficit, TSS, and Intensity Density of all of our sessions) as well as looking at completed workout compliance to see where users typically have issues completing sessions.
While you will see some reductions in TSS in those 23 adjusted workouts, none of them are easy. It is important to keep in mind that training does not need to be maximal to be effective. In fact, having workouts that are possible to be completed without completing depleting yourself is in fact much better in the long run.
Being able to consistently finish workouts is better for building physical capacity and confidence than is continually hitting a point of failure. You can see an analogy of this philosophy in use by Eluid Kipchoge - the best marathon runner - with references to these ideas at: Brad Stulberg Reveals More About 'Groundedness' and Getting Ahead
Also, keep in mind that any TSS value for any workout (and the associated changes) will vary for each user based on their unique 4DP. The concept of Intensity-Density that we are working on is going to be a much better representation of training load/intensity than TSS…but still isn’t completely ready to be included…but stay tuned!