For a significant period of time now, the go to power test for cyclist to determine their “threshold” or “FTP” has been the 20 minute power test, followed by an assumption that 95% of that given power is sustainable for an hour and that should be taken as your “Functional Threshold Power” (Allen & Coggan, 2010). However, using this to determine your training zones may leave certain interval sessions, especially those with a more anaerobic training impact too difficult for some and too easy for others and more importantly miss the desired stimulus.
The greater the anaerobic contribution to the effort the less reliable the calculated training zones from the 20 minute test are as shown by the graph above comparing the power duration model of different athletes. What does this tell us?
Critical Power
Well, it is clear that we need to test the ability of both the aerobic system and the glycolytic system in order to get a clearer understanding of an athlete’s physiology. This is where the well-researched “Critical Power” comes into play. Critical power is defined as the highest power that can be sustained in a quasi-steady state manner and the duration that CP can be held for varies athlete to athlete. The critical power test takes a combination of maximum efforts between 3 and 15 minutes (for the most accurate calculation) and calculates an athletes CP. This calculation can be done with just two maximal tests (usually 3 minutes and 12 minutes) but the more the merrier for the most accurate overview of the athlete’s physiology. Whilst CP and FTP have similar definitions CP commonly provides a greater value. CP also brings another metric into play and that is W’ (pronounced W prime). This is the amount of work that an athlete can sustain above their critical power and can be useful to create a pacing plan for short time trials of a shorter duration of their time to exhaustion at CP. A math equation is used to determine both CP and W’. The CP model has been extensively researched and is one of the most accurate field tests to determine cycling thresholds.
WKO5
A very similar model to this is the “Power Duration Model” built into the WKO5 data analysis software. This uses an athletes peak performances over every duration in which it has a data point for, in order to create a power duration curve and a modelled FTP (mFTP). Used correctly over a good period of time this can track changes in mFTP, time to exhaustion, aerobic and anaerobic contribution to a given power output and many other useful metrics. When used correctly this has shown to be the most accurate field-based method to track the physiology of a cyclist.
Laboratory Tests
Now a further, and more expensive way to determine your thresholds is laboratory-based testing. Whilst expensive this can provide useful information such as gas exchange ratios, blood lactate levels, maximal aerobic power and others. In my opinion with experience carrying out these tests, they are very useful for tracking progress over time, however the data is less useful for transferring out for use into the field where different environmental conditions are at play which affect the values. This is the case with any physiological testing, however laboratory-based tests are the further from real world performance than field-based tests. If your purpose for testing is to track metrics and you have access to this equipment then I would recommend that you use this, however if you are just looking to gauge a threshold estimate for day to day training then a field based test is more useful.
My Recommendations
In order to determine and keep track of your cycling thresholds, I would recommend utilising the Critical Power model. This is the most scientifically researched and backed field-based test for cycling specifically and is easily repeatable and cheap. You can even find a calculator for CP and W’ online if you don’t want the hassle of calculating it yourself or paying a coach to do it for you. Here is a solid protocol which you can try and repeat:
Ensure you are well rested and not carrying unnecessary fatigue into the testing.
A solid, personalised warm up of 20 minutes or more before each maximum effort (learn what works for you).
Test day 1: 3 minute all out test
Test day 2: 5 or 6 minute all out test
Test day 3: active recovery ride of 30 minutes to an hour
Test day 4: 12 minute all out test
Test day 5: Rest day
Test day 6: Take it to the next level, take your calculated CP and complete a time to exhaustion test. Ride at CP until you can no longer.
This will give you a great overview of your physiology at a given time with many useful data points to track improvements from. Try repeating this before and after a training block to track your progress, or alternatively use this in conjunction with the WKO5 software to create a power duration model and learn how to manipulate your training to improve power over desired durations specific to your goals! It is useful to note that this is a fairly intensive testing block, so it may not be repeatable as often as other tests, however it will provide an extremely useful dataset. Alternatively get yourself a coach who can prescribe you individualised training zones that cater specifically to your physiology and goals.
So lets come full circle, is the 20-minute FTP test dead? Unfortunately, it depends. It’s fair to say that taking 95% of your 20-minute power and assuming that’s enough information to determine all of your training zones is insufficient, but if you are looking to specifically improve 20-minute power or training for an event that requires 20-minute efforts then test it and implement a training protocol which is based around improving it! This goes for any power duration you are looking to improve, no one training or testing protocol fits all unfortunately and if it did, I would be out of a job!
Thanks for reading, if you have any questions or would like to enquire about cycle coaching, please don’t hesitate to get in touch.
References
Karsten, B., Petrigna, L., Klose, A., Bianco, A., Townsend, N. and Triska, C. (2021). Relationship Between the Critical Power Test and a 20-min Functional Threshold Power Test in Cycling. Frontiers in Physiology, 11. doi:https://doi.org/10.3389/fphys.2020.613151.
Craig, N.P., Norton, K.I., Bourdon, P.C., Woolford, S.M., Stanef, T., Squires, B., Olds, T.S., Conyers, R.A.J. and Walsh, C.B.V. (1993). Aerobic and anaerobic indices contributing to track endurance cycling performance. European Journal of Applied Physiology and Occupational Physiology, [online] 67(2), pp.150–158. doi:https://doi.org/10.1007/bf00376659.
Kenny, G.P., Reardon, F.D., Marion, A. and Thoden, J.S. (1995). A comparative analysis of physiological responses at submaximal workloads during different laboratory simulations of field cycling. European Journal of Applied Physiology and Occupational Physiology, 71(5), pp.409–415. doi:https://doi.org/10.1007/bf00635874.
Hill, D.W. (1993). The Critical Power Concept. Sports Medicine, 16(4), pp.237–254. doi:https://doi.org/10.2165/00007256-199316040-00003.
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