4dp is nothing new...back in 1999, Friel proposed essentially the same approach, but with (IIRC) eight "dimensions" (i.e., reference durations), spanning from just a few seconds out to many hours.



The problem with Friel's approach is that it is too cumbersome, and fails to recognize that muscular metabolic fitness (for which FTP is a surrogate) is the single most important physiological determinant of performance over any duration longer than a few minutes.



Because of the above, in 2000 I described training LEVELS that use FTP as an anchor point. As I emphasized at the time, and have pointed out numerous times since, such LEVELS (not zones) are meant to be primarily descriptive, not prescriptive.



Despite my efforts, many (including Sufferfest, at least up until now) have naively and mistakenly used my system to PRESCRIBE training, often via "canned" programs/workouts that don't entail direct input from a coach/direct interaction with the athlete.



Since FTP is a surrogate for the single most important physiological determinant of performance, this last approach still actually works, at least across most intensities/durations. However, issues can arise during supra-FTP efforts, since individuals can and do differ in their resistance to fatigue under such conditions.



To try to fix the problems created by their own initial, naive mistake, the folks at Sufferfest now claim that "FTP is dead" and that they have invented a novel approach that is better. In reality, however, all they have done is wind the clock back to the end of the previous century, prescribing workouts based on reference maximal efforts of the same durations I originally used to construct the power profiling tables. Not only is this a step backwards, it fails to fully recognize that, e.g., a maximal 1 min effort does not represent the same physiological strain for all individuals. (This is why iLevels, which provide individually-optimized targets for both power AND duration, were invented).

