estimating FT from 4min effort

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i've read that 115% of your 4minute power is equal to your FT. but, correct me if i'm wrong, from what some people on the thread have said is that a better estimate is 120% of your 5minute power. which is more reliable.

i've read that 115% of your 4minute power is equal to your FT. but, correct me if i'm wrong, from what some people on the thread have said is that a better estimate is 120% of your 5minute power. which is more reliable.
the way i'm reading your post, they are both way off, as you can see yourself probably.

my FT is about 75% of my 5 minute power, but i've got a huge anaerobic capacity to play with, so i imagine most people will be at a bit higher percentage than myself.

i've read that 115% of your 4minute power is equal to your FT. but, correct me if i'm wrong, from what some people on the thread have said is that a better estimate is 120% of your 5minute power. which is more reliable.I think you mean the reverse (i.e., 4MP=120%FTP), but this number is going to be highly variable due to the differences in AWC. For example, my 4MP~125%FTP, because I have a relatively high AWC. Another cyclist with a relatively low AWC might have a 4MP as low as 110%FTP. As you go down the power/duration curve, the standard deviation will rapidly increase.

Finally, some stat in which I excel!
My 4 min power is 42 percent higher than my FTP. :)

i've read that 115% of your 4minute power is equal to your FT. but, correct me if i'm wrong, from what some people on the thread have said is that a better estimate is 120% of your 5minute power. which is more reliable.
And I've read that the 4 min power is close to one's VO2max, depending, of course, how is the test performed. E.g., wether here is referred to an incremental test, or a 4 km pursuit.

I think you mean the reverse (i.e., 4MP=120%FTP), but this number is going to be highly variable due to the differences in AWC. For example, my 4MP~125%FTP, because I have a relatively high AWC. Another cyclist with a relatively low AWC might have a 4MP as low as 110%FTP. As you go down the power/duration curve, the standard deviation will rapidly increase.apologies. so using 5min to determine FT is much more concrete? is 5minute power a good indicator of aerobic and anaerobic power?

apologies. so using 5min to determine FT is much more concrete? is 5minute power a good indicator of aerobic and anaerobic power?No. Your anaerobic capacity will influence your max power all the way out to ~20mins. There's not much difference in the influence it has at 4min vs. 5min. If you want to get a more reliable estimate of FTP (short of doing a 60min test), try doing a 20min max power ride (rested) and take 95%. But, bear in mind that AWC even influences your 20min power. For example, my FTP is closer to 92% of my 20MP.

No. Your anaerobic capacity will influence your max power all the way out to ~20mins. There's not much difference in the influence it has at 4min vs. 5min. If you want to get a more reliable estimate of FTP (short of doing a 60min test), try doing a 20min max power ride (rested) and take 95%. But, bear in mind that AWC even influences your 20min power. For example, my FTP is closer to 92% of my 20MP.

Indeed, IMO the variation in the ratio of 20 min power to functional threshold power is sufficient that it's generally not worth doing a formal 20 min test (since you can estimate functional threshold power just accurately via a number of other, more convenient, ways). The exception would be if you want to use 20 min as one of the points in a critical power analysis...which the OP may wish to do, since (s)he apparently already has another point (i.e., 4 min power) that could be used.

Indeed, IMO the variation in the ratio of 20 min power to functional threshold power is sufficient that it's generally not worth doing a formal 20 min test (since you can estimate functional threshold power just accurately via a number of other, more convenient, ways). The exception would be if you want to use 20 min as one of the points in a critical power analysis...which the OP may wish to do, since (s)he apparently already has another point (i.e., 4 min power) that could be used.But, I think it (20min test) is a concept that is getting engraved in stone. I guess the idea of doing a full hour at or near one's max power (plus the difficulty of finding an appropriate course with a consistent grade and without stop lights or stop signs) compels people to search for a way of estimating FTP based on a shorter duration. Which, in turn, leads them toward a conversion metric (e.g., .95x20MP). All of which ignores the relative contribution of AWC to FTP and the inherent biases of using shorter durations for estimating FTP. But, the good news is that most of the errors are self-correcting when one begins doing high-intensity efforts with short recovery durations because if FTP is under- or over-stated it will soon become obvious. Personally, I still favor the 3-test protocol and use of the CP Model, because one gets so much more than simply an estimate of FTP.

As RD has stated, my reason for using the 20-minute method is due to the hilly nature of my surrounding area. Here's the elevation profile of a loop near my house. As you can see, it's hard to find even 20 minutes of semi-constant conditions, let alone an entire hour.

As RD has stated, my reason for using the 20-minute method is due to the hilly nature of my surrounding area.

That's true for many...however, it doesn't explain why you don't rely on other methods, e.g., inspection of ride files, normalized power, critical power testing, etc., to determine your functional threshold power. These other methods are really just as precise, and are either more convenient (in that they don't require formal testing) or provide more information (as Rapdaddyo alludes to).

That's true for many...however, it doesn't explain why you don't rely on other methods, e.g., inspection of ride files, normalized power, critical power testing, etc., to determine your functional threshold power. These other methods are really just as precise, and are either more convenient (in that they don't require formal testing) or provide more information (as Rapdaddyo alludes to).

i think this has been touched on before but my absoulte 5minute power is 475watts and i have done some crits with short 300-400m climbs and have gotten NP5minutes power estimates of 540+?? i can't figure it out and i know that its not accurate.

another thing relating to cyclingpeaks- sometimes i'll ride the morning before a race with the srm recording interval on 5sec and then for the race i'll change it to 1sec, but when i download it to CPS it comes up with some crazy 700TSS is there anyway to avoid that other than keeping the recording interval the same.

i think this has been touched on before but my absoulte 5minute power is 475watts and i have done some crits with short 300-400m climbs and have gotten NP5minutes power estimates of 540+?? i can't figure it out and i know that its not accurate.

Actually, you have figured it out: the normalized power algorithm isn't accurate during such short efforts, in part because anaerobic capacity makes a significant contribution to your power output.

another thing relating to cyclingpeaks- sometimes i'll ride the morning before a race with the srm recording interval on 5sec and then for the race i'll change it to 1sec, but when i download it to CPS it comes up with some crazy 700TSS is there anyway to avoid that other than keeping the recording interval the same.

You could download the morning ride before changing the recording interval.

Actually, you have figured it out: the normalized power algorithm isn't accurate during such short efforts, in part because anaerobic capacity makes a significant contribution to your power output.



You could download the morning ride before changing the recording interval.i think that even still it miscalculates TSS