The Myth of Functional Threshold Power (FTP)

“If you repeat something long enough people will begin to believe it’s the truth.”

 

 

How can I set training zones based on power? Are they accurate? Are they based on evidence? These are just some of the basic questions those looking to base their training on power. One of the most widely used and accepted methods of setting up training zones are based on what is know as the “Functional Threshold Power (FTP) test”. We see it used by coaches, listed in the magazines, and now it’s proliferated into online virtual training platforms and virtual reality training platforms such as Zwift and TrainerRoad.

However, what is the scientific basis of the FTP test? Does it measure / reflect lactate threshold? What are its limitations? Are there better options? In this blog and want to take a real look into the limitations of this suggested method of setting up a training program and why I believe it’s not all its suggest to be.

*In advance there is a little bit of physiology and some discussion of studies in the following blog. This sometimes breaks up the flow of a discussion but try to stick with it as it should help explain my views on FTP.

**November 2017 BLOG UPDATE: Please see comments and clarification following the publication with Dr Coggan, regarding FTP tests. 

FTP or Critical Power

The basis of FTP and other measures of so-called ‘threshold testing’ is defining that point between energy being primarily supplied by the aerobic system (i.e. sustainable over a long time) and the anaerobic system (sustainable over a short period of time).

According to one of the main academics behind the FTP test; Dr Andrew Coggan[1] states, “FTP is the highest power that a rider can maintain in a quasi-steady state without fatiguing for approximately one hour.” In addition it is suggested that the best predictor of performance is performance itself – so a 60-minute time trial is just that a great predictor of 60 minute time trial. Because 60minutes is often very difficult (especially the relatively untrained) its suggest by Coggan that a 20minute test can be used, which is described as underestimating the 60minute test by 5%. Knowing this the 20minute test is suggested as a means of determining FTP.[2] This is interesting as a description of the test but what is the scientific basis? Why should we use it (or not) to develop training zones?

The underlying basis of the FTP test is touted as being 1. Being representative of lactate threshold (See Figure 1) and, 2. The mathematical concept of critical power (CP). So lets take a look at both of these with reference to the FTP test.

 

Figure 1

Figure 1. Here we see a test of lactate threshold with a subject working and increasing power and lactate levels rising at a relatively low rate until a threshold (LT) is reached where any additional increase in power output results in an almost exponential increase in lactate.[From Coggan AR. Training and racing using a power meter: an introduction. 2003. Accessed online at: www.ipmultisport.com/ref_lib/Coggan_Power_Meter.pdf].

 

Lactate threshold and FTP

One of the main studies cited as supportive of the 60minute FTP test as being reflective of lactate threshold and a pragmatic approach to non-lab based testing is that by Coyle et al. [3] In this study 14 male endurance athletes where used. The cycling lactate threshold test was based on testing at 5 different intensities and looked for a 1mmol (a blood measure of lactate) change on blood lactate above baseline as representing the balance between lactate production and use.

The performance test was cycling until fatigue at 88% of maximum (Vo2max). The study split the group into 2. One group (HL) that could work at a higher % of the maximum at lactate threshold (72-86%) and one at lower level (LL) (59-71%). The results in terms of time to fatigue for the LL group (working at 34% above threshold) and the HL (3% below threshold) was as follows.

Time to fatigue in the HL group was 60mins and the LL was 29mins.

Therefore, how can was state that a 60 minute FTP performance test can be related to this study and lactate threshold when the LL group did not work at lactate threshold but 34% above it. Similarly, the HL group although lasting on average 60mins, when we look at individual subjects we have one lasting 75minutes and another only 51minutes be fatigue. That’s a possible variation of 24Minutes between subjects? As such we cannot base any type of assumption that the FTP test is reflective of any type of late threshold based on the results of this study.

Given that subjects during the test where not aware of the elapsed time this perhaps speaks of the inherent variability and weakness of the FTP test i.e. how motivated are you to perform? When the real question is when does lactate threshold occur.

Therefore, I am not convinced that a 60minute test can predict accurately where the lactate threshold is or power at lactate threshold (or at least not without possible significant variability). Although there is no doubt a relationship between Lactate threshold and time to exhaustion that does not mean that time to exhaustion or max power produced over 60 minutes is an accurate value to determine training zones.

 

The concept of critical power (CP)

The critical power (CP) test was the mathematical basis of FTP in many ways but it when we look at what the CP test involves it not merely a 20 or 60minute performance test.

The relationship between power output and fatigue was initially introduced by Hill (1927).[4] However, it was Monod and Scherrer (1965)[5] that coined the term ‘Critical power’. These researchers investigated the relationship between power output and time to exhaustion during multiple bouts of exercise on specific, isolated muscle groups. They then derived a mathematical equation that defined the relationship between power output and time to fatigue. This test involved 4 -5 bouts over a time period of 2 – 24 minutes and the data then entered into the equation to define CP.

We can already see limitations to this work – as they say ‘no muscle is an island’ as such testing a single muscle group would not be reflective of the physiological stress brought about during cycling where we see modern day application of FTP. So what about looking at a more relevant studies.

One of the primary papers referenced as underpinning the suggestion that CP is representative of maximum lactate steady state (MLSS)(i.e. just below lactate threshold where there is a balance between the rate of lactate production and the rate of lactate removal primarily representing aerobic system) or just above it is that by Poole et al.[6] In this trial a cycling test was used to assess the relationship between power and MLSS. Similarly, we see other studies referenced to demonstrate a relationship.[7]

 However, although there maybe a relationship that does not mean accurate. For example I might say driving when the group is icy may result in a 60% chance of a crash but 60% although significant does not predict it will happen. In assessing the accuracy of such a relationship last year Maturana and collegues[8] demonstrate that CP (calculated in tests over 1-20mins) over-estimated MLSS by 20w (based on subjects with a threshold of about 255w). That’s an 8% overestimation and although it may not sound like much if you cycle 20w above MLSS it will result in a continual rise in blood lactate ending in subjects fatiguing before the end of the test.[9] These results have been further repeated by studies from the likes of Bull et al, which demonstrated that CP overestimates the power output that can be maintained over 60minutes. [10]

Finally, the calculation of CP is highly impacted by the mathematics employed to identify CP, as is training status of subjects and pedalling frequency (higher cadence resulting in lower CP and FTP).[11]

As such this general view amongst people that CP and FTP are representative of lactate threshold is clearly flawed and at best controversial among scientists. Therefore, care should be taken to base any type of training program on the basis that FTP or CP is an accurate representation of an athlete’s true threshold.

 

What else does FTP testing not tell us as athletes?

An important factor in developing an effective training program is to know what our physiological strengths and weakness are. As part of determining where there are weaknesses we need to look at factors such as aerobic or anaerobic capacity, or economic an athlete maybe (the oxygen cost of cycling at certain intensities). What we get from FTP testing is one value, ‘a performance measure over one hour’. We do not get a measure of oxygen cost (or oxygen cost per watt – economy), lactate threshold, or similar measures that are independent of psychological motivation to complete a test to full exhaustion. In fact in most lab-based test of aerobic capacity most can generate a value well before physical exhaustion.

Another important factor is the assessment of fuel use across a given range of exercise intensities. What I mean by this is how much fat (grams/min) and carbs (grams/min) are you burning to maintain a given effort (say 200w vs. 250w). You may ask why is this important?

Well for any event exceeding 2.5-3hours in duration it can be massively important as the results from sub-maximal and max testing can give and indication of how much carbs we would need to take on board (based on stored carbs or circa 400-500g) to get us through an event. For Ironman based events such information can be vital to effectively determine pacing and nutritional (Carb) intake requirements.

So what about the practicalities of getting testing carried out in a lab (no I don’t do such testing)? A submax (check of bodies response to aerobic up to threshold work), max (anaerobic capacity and maximum oxygen uptake), and LT test carried out for cycling and running may cost in the region of £300-400 in the UK. For cyclists only needed a bike test or runners needing a run test its going to be half this cost. When you think about the money spent on a new wheel, helmet or the latest watch such costs spread over the course of a year should not break the bank for most. The data from such testing should not be under estimated and can be massively important in tracking fitness but more importantly identifying how a training program should be structured and how much time dedicated to base, build and comp specific periods.

 

Conclusions

So whilst testing FTP are great as a performance measure and I do believe performance is the best measure of performance its limited as a tool for accurately setting up training zones. However, few of us compete in only 20minute time trials or even 60-minute time trial. As such I would rather base my performance on a performance trial that is closer to what I would experience in a race. The problem is I do Ironman and other than jumping into a half Ironman I don’t thing any performance test would be appropriate.

FTP repeated over time can help be a measure of improvement in fitness/ performance once any learning effects are overcome (i.e. the first time you do an FTP test you may go out to hard and burn out, the next time you will pace better, spreading the effort over the 20mins). However, what I am discussing in the blog is the data in the scientific literature. Maybe tomorrow a new study will find some other reason why the FTP 20 Min test is accurate as a measure of threshold, however, until I see that evidence I can only base my views of what I have read so far.

For setting training zones I want to know how my body is reacting internally – so how much oxygen, carbs, fat am I using at given intensity (heart rate, power, or velocity) and how much lactate I am producing. Psychologically, I cannot significantly control my lactate response of the amount of oxygen my muscle consume for a given power, yet I can control how hard I feel I am pushing for the FTP test.

I am sure many coaches would swear that FTP is a great way to monitor athletes and set up training zones but is this because they don’t have access to other forms of testing? Is it because FTP is quick and easy, needing limited equipment? Have they actually looked at the other options? The bro-science response well my athlete did x or qualified for Y using FTP is not a response to the limitations discussed above. Maybe if they used other ways to set up training their athletes would have achieved their goals earlier, or perhaps many of their athletes don’t achieve but they just pull out those that have as a defence.

In conclusion FTP has its limitations and if it works for you as a coach or athlete and you improving year on year then keep on using it. However, don’t do it blindly, always consider why you are doing something what are the limitations? Is it based on real evidence? I will in later blogs look at the other measure I mention above such as lactate threshold, Vo2max etc but for now I hope you find this blog useful.

Keep training and best of luck for 2017!

Ps. I asked some of the key authors behind the FTP test for comment on what I feel are the limitation before writing this blog but received no response.

 

References

  1. Hunter A, Coggan A. (2006) Training and racing with a power meter. VeloPress, Colorado USA.
  2. Ibid, pg.51
  3. Coyle EF, Coggan AR, Hopper MK, Walters TJ. Determinants of endurance in well-trained cyclists. J. Appl. Physiol. 64:2622-2630, 1988.
  4. Hill AV (1927). Speed and energy requirement. In Muscular Movement in Man, pp. 41–44. McGraw-Hill, New York.
  5. Monod H & Scherrer J (1965). The work capacity of a synergic muscular group. Ergonomics 8, 329–338.
  6. Poole DC, Ward SA, Whipp BJ. The effects of training on the metabolic and respiratory profile of high-intensity cycle ergometer exercise. Eur J Appl Physiol. 1990;59:421–9.
  7. Pringle JSM, Jones AM. Maximal lactate steady state, critical power and EMG during cycling. Eur J Appl Physiol. 2002;88:214–26.
  8. Maturana FM, Keir DA, McLay KM, Maurias JM. Can measures of critical power precisely estimate the maximal metabolic steady-state? Appl Physiol Nutr Metab. 2016; 41: 1197–1203
  9. Ibid n8, pg 218, 222
  10. Bull AJ, Housh TJ, Johnson GO, Perry SR. Effect of mathematical modeling on the estimation of critical power. Med Sci Sport & Ex. 2000; 32 (2), 526–530
  11. Barker T, Poole DC, Nobel ML, Barstow TJ. Human critical power – oxygen uptake relationship at different pedaling frequencies. Exp Physiol 91 (3), 621-632.

5 thoughts on “The Myth of Functional Threshold Power (FTP)

  1. Mark,

    Your blog entry just came to my attention. I am sorry to say that it contains several critical inaccuracies. First, I have never claimed that FTP was *equal to* LT, estimated using Ed Coyle’s “1 mM above exercise baseline” approach, or any other. Second, I have never suggested that people use 95% of their maximal 20 min power to estimate FTP. Quite frankly, I am surprised that anyone with a doctorate (in any field) would make such adamant claims without thoroughly researching the topic they are discussing.

    Andy Coggan

    • Hi Andy,

      Thanks for your email. I did reach out to you via email on 4th March to get some comment from you before I posted the article, which I have just forwarded to your email. In relation to your comments. Its a shame you feel I did not research for this blog and of course I am no ‘expert in this area’ (my area is nutrition) hence reaching out to you for comment. However, like any good writer I try to ensure I do the best I can to make sure the readers can read all my references used and of course like any good debate can respond to my posts (isn’t that how people share and learn).

      However, I did not just take a look online to the may forums and websites of coaches that also seem to have came to the same view and reference your work. I used the following source material:

      On page 4 of your pdf paper ‘Training and racing using a power meter: an introduction’ downloadable here https://www.researchgate.net/publication/237251583_Training_and_racing_using_a_power_meter_an_introduction you write:

      “Given the limitations of laboratory testing as discussed above, probably the easiest and most direct way of estimating a rider’s functional threshold power is therefore to simply measure their average power during a ~40 km (50-70 min) TT. This highly pragmatic approach is justified by laboratory research showing that the power a cyclist can generate for 60 min correlates very highly with, but is slightly greater than, their power at LT (defined as a 1 mmol/L increase in blood lactate over exercise baseline) (2).”

      As per below does this not mean the same as:

      “FTP was *equal to* LT, estimated using Ed Coyle’s “1 mM above exercise baseline” as per the blog?

      It sounds similar to me but perhaps I am misinterpreting?

      Regards the 95% I believe in your book ‘Training and Racing with a Power Meter’ it states:

      “The reason for subtracting 5 percent of the watts from your 20-minute test is that FTP is defined as the highest average wattage or power that you can maintain for 60minutes.”

      https://books.google.co.uk/books?redir_esc=y&id=pPY5CgAAQBAJ&q=95#v=snippet&q=20&f=false This can be accessed online at

      In addition on page 51 of that book it states regarding the ‘threshold test’ the following:

      “Once the test is over and you have downloaded the data, you will need to figure out what the average power was for the entire 20-minute effort. Then you take this number and subtract 5 percent from it. The number that results will be your functional threshold wattage value.”

      Does this not equate to you suggesting people use 95% of the maximal 20 minute test to estimate FTP?

      Would be great to hear your thoughts, and happy to amend the article based on your comments.

      Best regards Mark

  2. Mark,

    1. The sentence in the chapter I wrote for USA Cycling refers to the fact that the subjects in the high LT group, for whom time-to-fatigue at ~88% of VO2max averaged 60.8 min, were able to maintain an intensity that was 9% (i.e., “slightly greater than”) than their LT as defined using Coyle’s method.

    IOW, correlation does *not* equal equality.

    2. Any book is always a group effort, in this case involving two authors and an editorial team. As I have pointed out in numerous presentations, posts, etc., the “95% of 20 min power” rule-of-thumb for *estimating* FTP is Hunter’s approach, not mine. *On average*, 95% is this appropriate correction factor to use, but there is sufficient variation between individuals that I have always preferred alternative approaches, including critical power testing, provided that the test durations are chosen appropriately, i.e., fall within the domain of validity of that simple mathematical model. (OTOH, I am not a coach dealing with multiple athletes spread around the world, so YMMV.)

    3. The above point about group effort also applies to the (mis)definition of FTP as being equal to exactly 60 min power.

    Simply put, if you really want to know *exactly* what *I* think, pay attention only to things where I have complete editorial control (e.g., messages to web forums), and take articles that are co-authored or edited by others with a grain of salt. In particular, be a bit wary of articles that combine “Dr.” or “Ph.D.” with “Andy” or with each other, as that’s a sure sign that someone else has had their finger on things.

    Andy Coggan

    • Hi Andy,

      Thanks for the responses.

      1. OK but when you read the text it did not read like that. I am happy to insert the term ‘correlates’ into the article. Or perhaps you can propose what you believe your testing by the 60 minutes if not a representation of lactate threshold? Are you saying that lactate threshold has no place with reference to FTP as the issue is just correlation rather than causation? As such is all FTP based training programs based on correlation between FTP and fatigue but in fact that relationship has nothing to do with hydrogen ion formation and related metabolic fatigue?

      2. OK – But for us readers we don’t know that. The chapter ‘Power based training: where to begin?” Does not state the author that wrote it. As such it was an honest mistake by my and the many many coaches that base training zones on this test and the related correction. I am happy to insert a note into the article that following clarification this is not the view of Dr Coggan – thats not problem and something we could have discussed back in March when I tried to reach out. I use WKO4 and as such value the insights from power based training and mix both CP testing and lactate as they offer different benefits and weaknesses.

      3. Yes great point and I tried to make that point in relation to critical power and where it came from historically. Perhaps you would like to write a brief article for the site clearing up the confusion (it would be unedited and only placed on the site after your approval – i.e. my fingers wont be editing). As I said I have no skin in the game at this time re FTP, LACTATE, Respiratory threshold etc in developing training zones. As an athlete i am (as you will see from the blog) look for anything that saves time and money in giving insight into how to effectively develop a training plan. I am sure if athlete knew the 95% of FTP rule was not always going to be accurate (as I have tried to say in the article) then they may consider other methods.

      I look forwards to hearing from you but i hope you can see that I had done my due diligence and where my views came from i.e. from books and article that i thought where by yourself.

      Thank you so much for your time and I believe this will help clarify a number of issues for coaches and athletes out there, and specifically the differing views between authors over where FTP testing and critical power testing may fit in their program design.

      Please email me if you would like to add content or and article or where you would like any corrections added.

      Regards Mark

    • Hmm.. I would in a humble way recommend dr. Coggan NOT to be a co-writer of papers/books that are inconsistant with his definitions and correlations and other strong beliefs.
      Of course we should be open minded on development on this topic. But as an example it seems strange suddenly to define FTP NOT to be an all out effort over 60 minutes as this has been the traditional interpretation.

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