mathematics wrote:
I've done over/unders as a cyclist because they can simulate bike race situations pretty well. I'm not sure if they're the right protocol for an IM. As with anything, it needs to be viewed in the context of overall training. Tangentially, FTP is fine, but not a very good measure of IM specific fitness. The 20min test is like 10% of the bike leg length, it's a good ballpark but quite non-specific. You could raise you FTP via VO2's and 20-min focused workouts and see little improvement in IM bike time. The bike leg of an IM should ideally have zero lactate accumulation (high production, but no accumulation, like <2.0mmol, depending on the athlete of course)
Now, are over/unders good for IM? There's probably better options. Over/unders (for me at least) are a pretty fatiguing workout, I feel them the next day and they definitely impact any workouts in the next 36-48h. If I'm doing a workout that leaves me recovering for that long it needs to provide a really good stimulus towards what I'm working on. For an IM that's ~4h bike power (LT1, basically). 3-4x40min would be a better option with similar recovery. or 3x60 going up in power, something like 85/90/95%FTP. The run is those are both 3.5-4h workouts, OU could be 60 min.
If you have generalized fitness gains on the table or are far away from upcoming races (months), then they could be a good option, even if for nothing more than providing a change of pace. Personally I prefer "peak/fade" over traditional over/unders. Sprint all-out for 20-30sec, then 8-10min at threshold. It stresses the same lactate clearing ability in a way that (for me) is less fatiguing.
Wouldn't 95% of FTP put you above LT1? Certainly below LT2, but I don't think I can remain < 2.00mmol at 95% FTP, maybe 80-85%? Or am I just really un-fit?