Best Wattage for X time vs interval wattage for X time?
 

So I've never really paid attention to the power curve on Strava, I mainly just scroll right past it. However, I was scoping it out the other day and noticed that my 8 minute best power for the last 6 weeks was a whopping 340 watts, so of course, rather than attempting to use the recommended 107-110% of threshold (295-305 watts) for my 8 minute intervals, I targeted 340 watts. I even used math to back-calculate that my FTP was an impressive 309 watts since the training I'd been doing has clearly been incredibly effective.

Spoiler--I maintained 337 for the first interval and then could barely hold 250 for the next two and bailed with 2 minutes left on the last interval.

So that had me thinking, what percentage of your best wattage for time are intervals typically done at? Where did the recommendation for 107-110% come from? FWIW, doing 3x8 intervals at 110% of my FTP is ******g tiring. If I had more base, would I be able to get closer to my 8 minute max on my repeated efforts?

Intervals should be effort based.

Max effort wattage and repeatable interval wattage are not the same thing. A true max effort (even down to 1 minute) could (should???) put a big dent in your anaerobic work capacity and "red zone" work for the rest of your ride. How much higher you can go over the repeatable effort depends on the athlete, the conditions and your body on that day. The repeatable interval targets should be based on a sound FTP test method and be somewhat reproducible, and therefore useful.

It’s a good question. I use Xert, which models max power at any duration, and it’s been accurate for me. If I’m doing interval repeats, I’m most likely going to cut the duration in half, ie 8 minute max power, but done for 4 minutes, or if I want to go even higher intensity, like 3 or 4 minute MMP, then I might need to make the work durations 1 or 2 minutes, like a Ronnestad or Tabatha.

I’m not really trying to give you a training prescription, more just describing what’s feasible, regardless of how you structure it. Some might do sets where they go closer to 1:1 (MMP to duration), and that depends on the number of reps of course.

Math sort of does not work to calculate FTP or intervals based upon short efforts due to the huge variation in W' from athlete to athlete.

107-110% of FTP is just a guesstimate.

With lots of max efforts and recent data, XERT is very good at predicting power levels along the curve up to maybe 20 minutes. The PD curve of a sprinter is different from a Rouleur or a Hill Climber. So, their interval prescriptions will be a little different even if preparing for the same type of event.

When doing an interval set like that (VO2 max), I tend to use 4-6 minutes depending on fitness and have an effort level that allows me to finish the fifth set or just fail. My 8 minute power is a little higher than yours and my 5 minute interval is around 330 watts but my percentage of type 1 fibers is relatively high and my W' is relatively low. I think the key is being just able to complete it five times with the last one being wicked hard to complete.

Lookup the concept of critical power if you're interested in this. I think that might fit with your question. I still don't completely understand it, but feel it's close to what you're discussing.

As for your first set versus second, that does kind of sound like the result of an all out one time effort for 8 followed by a flop. But 340 to 250 is drastic. I would have thought maybe a drop to upper 200's like 280, 290, or even 300 for the next set.

I don't know the term for when this is the case, but there's a word for when a person cannot repeat or recover well from strong single aerobic efforts. This sounds like it.

If you can do 340 for 8 once, the next set 300 would be tough but entirely doable.

Also caution on the percentages. Folks who aren't as "deep", those percentages should lag a bit. So instead of 95% of 20min many folks should do more like 92%. Shoot, some maybe even 90%. Then same thing for guessing at short intervals to long.

I ride with plenty of folks that can do 300 for probably 20min. Or 320 or so for 8min. But the number that could do an actual 280 or 285 for an hour, or 260 for 2 hours is much much slimmer.

I'll have to read more about critical power. I'd say that I'm basically in the "not particularly deep" category though. I'm a 35 year old father of two with a full time job, so I'm lucky to get 5 hours in per week. Most of that is at steady state intensity or higher, and I can imagine that it might bias me towards anerobic efforts rather than aerobic ones.

For repeatability at duration x, I typically just go reallllly hard but not all out hard relative to what I know I can hold at duration x.

For building max power at duration x, I go as hard as I can for duration x without regard for what watts I can push in the following intervals.

For shortish intervals like that, if you felt like you were a fish trying to breathe out of water - regardless of the watts you were pushing - you were probably doing it right.

More CTL/TSS per week in general lends itself to more repeatability because you can handle more sets of the same workload. IMO. I base that opinion off of pros doing sooooo much volume and being able to do sooooo many repeats in races of stuff.

I thought that was a comment in the "Time Crunched Cyclist" book. The intervals done by a low volume cyclist mean you can do those, but not as many as a non-time crunched person can do. So the book claimed to "use your matches wisely".