I'd like to try and bring this issue to rest, once and for all, if I may.
For the moment, forget the idea that FTP represents some power that can be sustained for some duration. Instead, think of FTP as the power that represents some level that, above which, the work rate cannot be sustained without having the athlete accumulate fatigue and eventually reach exhaustion and below which the athlete is able to recover from fatigue. In Xert, this is simply Threshold Power (TP).
In Xert, we also introduce another parameter that detemine how much capacity you have above TP. This is called High Intensity Energy (HIE). And we also add in your highest power possible - Peak Power (PP). With these three parameters, called a "Fitness Signature", Xert models your fatigue as it increases with efforts above TP and decreases with efforts below TP, ultimately defining how much power you have available at any given moment - Maximal Power Available (MPA).
An athlete's Fitness Signature remains remarkably stable from ride to ride. This is great since the changes in Fitness Sigature variables are small, when efforts to exhaustion are performed, and we can readily see how your fitness signature parameters move up and down with trainig load. We can spot progress as the changes are in very many cases tied to the amount and type of training an athlete has been doing. Your Fitness Signature therefore becomes a set of variables that can be used to *define* your fitness level.
So how do we tie TP to other values that appear to be analogues, namely FTP or CP? We've seen the debates that have raged over how FTP and CP compare. If you use the Xert Fitness Signature calculator (
https://www.xertonline.com/calculator), it takes 3 maximal, constant work rate efforts and determines the Fitness Signature and from the Fitness Signature, will plot out a power duration curve. This process is *not* a regression but a *solution* to the three points provided.
What you'll notice however, is that if you replace a data point with a very high power - 2000W for 1 second - the model mimics the 2-parameter CP model. But as soon as you reduce the 2000W to something more realistic, TP drops below the same value calculated for CP. So where there have been assessments as to how long CP can be sustained, TP would exceed that duration *whatever that duration may be*.
So how long can one sustain TP? To answer that question, we also have to ackowledge a couple of other phenomenons that we see in the data. Firstly, the prevalence of 1-hour efforts that end where our model-derived MPA and power meet at some value near TP is *extremely rare* in regular ride data. One might argue that our MPA isn't modeled correctly but the most likely reason is that athletes are simply unwilling to spend 1-hour at slightly above TP such that MPA drops over the course of the hour. In Xert, we introduced the concept of Difficulty Score as a way to quantify how hard an effort is to complete and a 1 hour effort slightly above TP has a very high Difficulty Score, suggesting that most atheltes would give up well before. Note that *giving up* means that they still had the capacity to continue but chose to stop or to reduce power below TP to avoid the discomfort. We also see that handling this discomfort improves with training, i.e. as traiing load increases, so does the athlete's capacity to handle greater difficulty increase.
The second factor is that TP and HIE (PP not so much) are affected over longer durations. We see them declining in order to determine MPA. With a declining TP over a 1-hour effort, this has the effect of reducing MPA for constant work rate efforts that we don't currently model in Xert. This is something we plan to add to the software.
In conclusion, if one simply looks at historical power data, it would be extremely rare to see a 1-hour effort that would have an average power near our model-derived TP. If this is how you choose to define FTP, then yes, TP overestimates FTP every time. In Xert, we use our fatigue-based model to look for a power level that is sustainable and determine this value using a consistent and repeatable method. We believe this is similar to how many athletes and coaches use FTP in training and thus see our TP and FTP as being the same in this respect. This value *could* be sustainable by the athlete for roughly an hour but the likelihood of this happening is limited by the athlete's willingness to endure the discomfort. Many think that they couldn't sustain our derived FTP for an hour when what they really mean is that they *wouldn't want to*.
Trev wrote:
I suggest you ask those that link FTP to MLSS why they have confidence in blood lactate testing, see below.
"As noted, MLSS is an exercise intensity that can typically be sustained for 30 to 70 minutes. Since FTP is a simplified tracking metric of MLSS, it has the same sustainable time range (not specifically one hour, as often stated by others). Since this roughly corresponds to the duration required to complete a 40km time trial, the latter provides an excellent estimate of power at MLSS, especially when you consider how flat the power-duration relationship is in this region. In addition to improved metabolic fitness being reflected in a higher power at MLSS/FTP, however, training also tends to improve the duration that exercise at this intensity can be maintained."
https://www.trainingpeaks.com/...tion-metric-in-wko4/ Kiwicoach wrote:
More hilarity. And your confidence in lactate testing is based on what?
But seeing you are neither a coach or a sport scientists what is any of your sad ramblings based on?
Does internet trolling pay well!
Trev wrote:
Yes, a high mFTP and Time To Exhaustion of 30 to 40 min can tell a story, that FTP defined as quasi steady state power for approx 60 minutes is utter garbage, yet for over a decade idiots thought that is what FTP was.
So what was the original definition of FTP? Obviously it was balderdash and things have moved on, yet people are selling apps which assume FTP is the power one can maintain for approx 60 minutes in a quasi semi state. But then, new FTP has moved on and FTP is the power one can maintain for anything from 30 to 70 minutes.
As New FTP is the equivalent of MLSS, people should go and get a proper power / blood lactate test and establish hard facts, instead of relying on snake oil.
Kiwicoach wrote:
Hilarious
Seems like many assumptions being made. Many take a percentage of a short effort or ramp test as an indication of FTP. 75% of 3min power or the Max Min Power test.
This is where the Fatigue Resistance metrics in WKO4 become quite handy. A high mFTP and 30-40min Time To Exhaustion can tell a story.
We have that here in Christchurch with short steep hills and riders who do maximal efforts up them but don't go as hard on the flat for longer durations. One chap rode a 25km TT at a lower power than his mFTP. Another chap did a 20min effort and a 40min effort and saw his mFTP increase with a TTE of 60min. For racing a Normalised Power target for the first chap would be much lower than the second chap.
Biggest thing I see with these short tests or estimates based off such short is a overestimation of FTP. Easy to spot in WKO4 if you look at the fatigue resistance metrics.
sciguy wrote:
So this continues;)
Armando Mastracci, Founder of
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