23 Oct Is FTP Really Dead – 6 Methods for Assessing Cycling Aerobic Fitness
I won’t make you hold your breath: it isn’t.
FTP is alive and well and still – in my opinion – a very worthwhile performance metric for cyclists of all stripes. Mostly what has changed is the addition of novel protocols for testing and fitness assessment – and of course a little bit of added marketing.
As a quick aside, we should cover the fact that there are a few terms that are largely synonymous – a real acronym salad: FTP, TP, LT2, AeT, MLSS (maybe), and CP (sort of). We can quibble about these terms, but they more-or-less all mean the same thing – the highest possible, steady-state cycling intensity (typically evaluated as mechanical power). For sake of simplicity and tradition, I will use FTP in this article.
The Coles Notes on FTP.
The acronym stands for Functional Threshold Power. It is the term that Andy Coggan coined when he first wrote about training with power. In general terms it is the highest power that an athlete can sustain for a period of 60 minutes. Very different things happen below FTP versus above it. Now there is a grey zone of maybe +/- 5% around FTP itself that’s a little murky, but safe to say that below 95% and above 105% of FTP are very different worlds (of hurt).
Knowing FTP is useful for both training and racing at many – bot not necessarily all – cycling and triathlon disciplines. Tracking it over time is an excellent means for assessing changes in aerobic fitness, and thereby making smart conclusions about the efficacy of a training program.
So how do we go about measuring FTP? This is where recent advances in both physiological and as well as computational research offer a buffet of options. Let’s look at 6.
This article is not a deep dive into any of these, just a quick summary of my personal, often triathlon-coach-biased experience and perceived pros and cons.
Maximal sustained power tests
These are the oldies but goodies of the bunch. Coggan was the first to popularize the well-known 20-minute maximal power test. It’s straightforward: warm up, then hold a maximal, steady-state power for 20 minutes. Take 95% of that value and presto: your new FTP.
Pros: free, easy to understand, easy to calculate
Cons: hard to execute well, not necessarily reliable, kinda sucks to do!
I’ve heard Peter Seiler talk about making his athletes do a 60-minute test instead of the 20’. There’s no more reliable way of making sure that you can hold your FTP for 60 minutes, but I would not want to be the athlete asked to do that on a regular basis!
Power duration curve tests
Dr. Philip Skiba (who became proper-famous for his work on Nike’s Breaking 2 project) popularized an alternate approach. He proposed that knowing any 2 (or better yet 3) points on the power duration curve (image below) will allow the athlete to extrapolate to any other point on that curve – including the 60-minute point. He called this Critical Power (CP). CP is typically said to be between 100% and 105% of FTP. Those two test points should include one short – say 3-minute or 4-minute maximal power effort – and one long – 12-minute or 15-minute maximal power effort. On top of CP / FTP, performing this test allows an athlete to calculate her anaerobic work capacity, or what Skiba called W’.
Pros: free, easier than the 20’ test to execute, calculating W’, more accurate than the 20’ test
Cons: not as accurate as a lab test, requires the use of advanced cycling software or online calculator
For years the concept of a steady-state threshold intensity was intimately tied to the production and clearance rates of blood lactate. Recently, I feel like that relationship has become more nuanced. Still the test procedure is generally the same: a stepped ramp test with blood drawn at each step to measure lactate concentration. Those lactate data points are then plotted against power and FTP is calculated at the second point of inflection.
Pros: more accurate than a field test, can detect the aerobic or lower threshold (LT1 / AT / LTP)
Cons: not free, dependent of skill of tester and calibration of equipment, holes in finger – admittedly very small ones.
Metabolic cart testing
This is the gold standard. Aside from getting at accurate numbers for FTP and the lower threshold, you will get accurate VO2max power (useful for VO2max-specific training), and metabolic data. It’s this last piece that I think is the real value of met-cart testing: accurate carbohydrate and fat combustion rates at different power outputs. This doesn’t matter much for the crit racer maybe, but it is essential to the long course triathlete.
Pros: the most complete suite of data including metabolic data
Cons: expensive, typically available only in performance labs and universities
INSCYD Sports Analysis Software
INSCYD is a worthwhile add to this list. They have been quietly making a name for themselves working with the likes of the Bora–Hansgrohe pro cycling team and coaches like Dan Lorang (Jan Frodeno, Anne Haug, etc.). I have only recently started speaking with them and exploring a partnership. They offer a potentially amazing product: all the data an athlete would get from a full metabolic cart lab test, with only a field test. I am honestly a little skeptical – stay tuned. You can also easily do an INSCYD test outside of a lab. I’m including them in this category because of the wealth of data they provide.
Pros: all the met cart data at a lower cost and without having to visit a lab
Cons: not free, may not be quite as accurate as a met cart.
Baron Biosystem’s Xert
Xert is not a testing methodology or platform, but it belongs in this list because it absolutely does calculate FTP – although they call it simply TP. Xert is a mathematical model that takes three parameters (I’ll use their terms) – TP, High Intensity Energy (energy expended above TP), and Peak Power) to calculate a rider’s complete fitness signature. This does take a few rides, but it is updated with every effort on the bike, making sure that it (typically) does not ever get stale. The only catch is that you need to regularly perform rides with elements above threshold. This is often not done by triathletes training for long course work – at least not during race-specific training. Still, it’s an awesome platform for road cyclists and short course tri folk, with useful applications to long course athletes too.
Pros: continuously updated fitness signature, no testing required – just ride, very inexpensive
Cons: does require regular supra-threshold efforts to maintain an accurate signature
Thanks for reading – that was a long one! Before I sign off, I want to once again touch on that lower / aerobic threshold. It is a concept that has not made waves in testing or training until recently. I am becoming a big fan, and if you’re a bike or triathlon nerd, you should be too! I’ll write about it soon. It’s worth it. I promise.