Are there physiological limits to a specific W/Kg?

Obviously there are limits to the time you can hold W/Kg (FTP) and it seems as though 6.5W/Kg seems to be the golden number however, is there a number/time that we should be saying is impossible for a pro cyclist to hold without the aid of enhancements? I know this is a slightly “length of string” question but, wondered if anyone had any good academic publications?

I also know that the recovery rates of pro cyclists allow them to continually hold high W/kg but there must be some point at which the body cannot function.

There are numerous physiologists who regard the ability to hold certain w/kg for certain lengths of time as suspicious, but there are lots of caveats. >6.5 for >45 minutes has been cited as the ‘impossible’ number, but it’s not straightforward. From my admittedly very amateurish grasp of all of this, I think >6.2 for >30 minutes when deep into a stage race is very questionable.

Can performance be used as an indicator of doping? - CyclingTips is an interesting read, as is Tour 2013 rest day: Pondering the unanswerables with physiological implications | The Science of Sport

While I don’t doubt that training and nutrition have moved on a long way since the 90s, the fact that we now have domestiques bettering the times (and, more importantly, estimated w/kg) of Pantani and Armstrong (highly talented riders and conclusively proven dopers) up certain Alpine and Pyrenean climbs after over a week of racing and over 100km into a stage is, well, eyebrow-raising.

And it’s the fatigue aspect that I don’t think gets enough attention. It is very, very impressive, but not wholly outlandish, for riders to knock out >6w/kg for 20 minutes. There are amateur TT riders who can do it. But the ability to do after 3 hours of hard racing is exceptionally rare. To do so after hours of hard racing after 2 weeks of the same is bordering on miraculous.

Purely personally, I strongly suspect that use of synthetic haemoglobin products is rife in the pro ranks, but I a) freely admit I cannot come close to proving that and b) genuinely hope I’m wrong.

Ultimately, if I were asked about some of the performances in this year’s tour, I would say they probably indicate doping, but fall short of proof beyond reasonable doubt.


Thanks for the reply; very interesting. I am not sure how credible the MPCC’c credibility figures are but, they are suggesting only 3 doping cases in cycling in the first three months 2020; which does not sound like a lot when we are seeing the dramatic speed increases. Perhaps, I am reading more into it but, it seems like the only way people are getting caught is by whistleblowing or investigative journalism.

There have been tons of advancements: everything from more dedicated training to power meters, to better nutrition and fueling during ridtes, to better understanding of aero benefits. All of these would dramtically improve the performance of the average professional rider. So, I don’t think some of this necessarily points to nefarious means. However, some of the numbers are starting to worry me, and I hope against hope that controls and testing are up to the job.


I very largely agree.

The difficulty is that these are arguments that were (in slightly different form) made during the 90s: we have been here before.

The (appropriate) analogy a French commentator made (I can’t remember if it was this year or last) was it’s a bit like suspecting your spouse of cheating. You don’t want to think it, you find plausible alternatives, and you want to be wrong, but at some point, when the same suspicious things keep happening, there are just too many things sensibly to explain away, and the simplest and most likely explanation becomes the worst.

The question is: are we there yet?


I don’t think W/kg isn’t the best metric to ferret out doping, and there a few reasons for that:

  1. As mentioned above, you have to be specific about the time interval over which power/weight is used
  2. It’s difficult to compare such metrics from different riders in different years on the same segment because to make a valid comparison, you need all of the variables (wind, temp, humidity, Crr, CdA, and other things that may influence the aforementioned variables). Not only that, but you’d need to know how those variables changed over a segment. It seems some “experts” are making assumptions about those variables and about power output over those intervals.
  3. The tech now is far improved now. A number of variables in #2 have improved. Training methods have improved. Everyone has power meters now (Pantani didn’t…did he?). Nutrition science is far more advanced.

The net result of that is that it’s very likely that it takes a lower W/kg figure to achieve a performance that surpasses one done by a doping athlete years before.

As for the MPCC’s graphic and claims, we know that cycling does more doping testing than pretty much every other sport. I think that the biological passport has made it a lot more difficult for dopers to get by in cycling. Couple that with the attitude brought into the peloton by riders that turned pro in the last 10 or so years, and I think it makes it much more difficult for doping and dopers to thrive in the peloton. Maybe that’s positive peer pressure.

Of course, there are still riders doping. You have to assume that if for no other reason than continuing to improve tests and create new tests and methods for rooting out dopers.

Okay, I’m longwinded.

The take-home point, I think, is that W/kg is meaningless as an indicator of possible doping without context, and if used, that context has to be very well defined. Without well-defined constraints and variables, using W/kg as an indicator of doping is a bit like trying to derive some meaning out of a graph whose axes aren’t labeled.


Honestly, I don’t really care if they all do or dont, but if they do that its probably a fascinating side of racing that It would be very interesting to the fans.

I genuinely believe that we are too conservative on the topic, if it is a matter of athlete safety then I agree but I would argue that many other things they do are risking their life, mental health etc.

A well-considered response and by and large, I agree.

Certainly, unless a rider or team publishes their power data, deriving that is based on a host of assumptions. Even if we (arbitrarily) say that >6.5 for >40 minutes clearly indicates doping, but (say) 6.3 for that time is just about feasible, the range and number of assumptions likely creates an error margin wider than the under/over line.

Having said that, doping with PFCs or synthetic blood products would not, AFAIK, show up in a blood passport. Moreover, they’re not (again AFAIK) routinely tested for.

Next, the aero advantages that are now so prevalent are at their least meaningful up long, steep climbs, and the bikes aren’t any lighter (in many cases, they’re heavier).

Finally, I am also very sceptical about a number of individual performances, which I won’t name, but anyone who watched the TdF can work out which ones I mean. It is unprecedented for a domestique to beat times which, let’s be clear, have stood for several decades now.

It’s an interesting analogy that many of the world best performances for women’s athletics that were set by heavily-doped Soviet or DDR athletes in the 70-80s are now accepted as being essentially unbeatable by clean participants, even though athletics training has also moved on since then. Perhaps tech has more of a role in cycling, and yes, it is harder to compare like with like, but we are essentially seeing supposedly impossible numbers being produced by riders without a history of that kind of achievement. In athletics, that would be greeted with deep suspicion. In cycling, it’s explained away.

I’ll finish a longwinded comment with a story I’ve told on here before. Our rowing coach at university was from the former DDR. He was fairly open about the doping protocols that went on over there, as they were state enforced. However, he was utterly adamant that clean elite sport was a myth, and that (by and large) dope tests caught only the unlucky, the stupid, or the under-resourced. Indeed, when one of the squad commented that they would love to watch an ‘untested’ 100m sprint final, ‘just to see what was actually possible’, this coach replied ‘you can watch that race every 4 years and have done so already’.

I’m sorry if this is all a bit cynical, and I wholly understand if people disagree.

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I was listening the Science of Sport podcast where they were discussing the concepts of Critical power and Wprime. It makes a lot of sense to me that your body is a battery and when you go above your critical power limit you use your battery up at joules/s amount. Plus that the battery never gets fully recharged over a stage race or even within a stage.

I think physiologically these elite athletes are operating at the extreme ends of the spectrum and agree that it is probably the average riders in the peloton that are the ones operating outside their limits. I know this was touted as the fastest TdF ever but it would be interesting to break that down into the peloton and/or across climbs/downhills where aero gains might be taken account of.

Sorry I did not start this as a doping topic (despite the obvious insinuation), I am a data nerd and love to understand these performances in context. I think we all love our cycling and want it to be clean but I am not sure what the answer is; do we blindly accept or do we expect more? Perhaps data is the way forward, more available data over the TdF with riders weights, power and speed data available real time. People can actually see the numbers then … won’t necessarily stop doping out on comp but would highlight impressive or confusing performances.

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I have said for a while that the teams should have to make every rider’s power data available to the UCI and WADA. Much as I’d love it to be public, I can see why they would fight that hard, as it could be a competitive disadvantage. But I can’t see why they could refuse to give it to the governing body.

Out of interest, I went out last night to see how long I could hold 6.5w/kg.

I’m 40, average about 200 miles a week, and race masters CX. I’m not ‘fast’ but I’d say by club standards I’d say I’m faster than most. I won a semi-competitive sportive earlier this year.

Anyone want to guess how long I could hold that wattage for? :rofl:


For an average person, 6.5 W / kg as a 6 minute power translates to a VO2 max of about 77 ml / kg.min

A long time ago in a galaxy far far away (when I was a competitive XC skier forty years ago) I was at that level. Unfortunately for me the Bjorn Daehlies of this world were up in the mid 90s, which translates to over 8 W / kg (6 minute power).

Were they clean? Who knows? It does illustrate that external factors have some influence because XC skiers routinely achieve VO2 max levels that pro cyclists would kill for.


It was less than 6 minutes…

That guys can do this for >20 minutes after 100km racing and deep into a stage race utterly boggles my mind. They might be doping, but I’ll tell you now that I could take all the drugs in the world and not get close to that, and couldn’t have done at 21, either.

I do recall reading somewhere that comparing elite XC skiers’ VO2 numbers (which as you note are insanely high) to cyclists is not quite apples to apples, as the full body involvement of skiing tends to produce higher numbers that don’t necessarily mean higher fitness. I don’t recall the details; I’ll have to see if I can find it.


Not really w/kg relater, but I think a lot of the avg. speed increase can be explained by the increased level of the complete peleton. Including tech, training, nutrition etc. Where previously only the top riders were at the very top level we now have 150 guys able to up the pace.

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Re max w/kg - is this a constant for all riders, or could it be dependent on weight?
You could imagine that it would plateau with riders above say 100 kg, or that very small riders could have a relatively larger max w/kg?
Any evidence out there that it is constant across a range of bodyweight?

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It’s very dependent on weight - that’s why wout van aert, for all his time trialing and sprinting prowess, will never be a GC rider. He just weighs maybe 10-15 kg more than someone like Pogacar or Vingegaard and the central aerobic system which is the bottleneck to climbing performance doesn’t scale linearly with weight/height/body-size

It’s an interesting conundrum.

On flat or rolling courses, pure watts beats w/kg all day. If you can drill it for 450w for an hour on the flat you’re going to be a hell of a time triallist or rouleur. But if you weigh 90kg, you’re going backwards quickly uphill at that level.

Conversely, some of the very small and skinny climbers can put out 325w at not much more than 50kg. The w/kg is great uphills, but they really struggle in crosswinds etc and will need a lot of protection.

The true gc guys sit between those two extremes.

The other really big factor, of course, is recovery/repeatability. There are probably 5-6 riders we could all mention who, on their day/for one day, can hang with Pogacar and go. But day in day out for 3 weeks? No chance. IMO that is probably the rarest quality the real greats possess.

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My obvservation is that the best GC guys are 65-70kg but have a frame which naturally would like to be 75-80kg.

It seems like at those sort of weights, when lean, you still have elite climbing w/kg with a decent enough engine (i.e. from the 75-80kg ‘chassis’) that can stomp a TT.

Of course TT is not just about the engine; aero and time spent practicing is huge.

Only other point that’s worth making is that the whole “limit of w/kg” discussion sometimes ignores how the w/kg is achieved. Think about how the TDF was raced this year - absolutely blistering attacks (had to be nudging toward 1000w kicks) followed by lulls (which looked around threshold), over and over.

That is very different to banging out 6w/kg for half an hour at steady state, a la Froome / Thomas / Wiggo.

Whether or not its more suspect, less suspect, I don’t really know or spend all that much time thinking about. I just figure that it’s pretty amazing and wonder if we’ll look back at this in 5-10 years time as another period of heavy dope use (or not).

I don’t know if the conclusions being drawn in this thread are right or wrong, but I think that there are two significant issues that I think are missing from the debate.

  1. If we are looking at times up climbs, then the way they are raced (Sky/TJV train v’s favourites kicking shades out of each other v’s GC leader solo and off the leash) makes a big difference. Sure #AeroIsMeaningless at the speeds I climb, but at 25-30kph up 5% grades it matters. Furthermore, even if the best of the peloton now is not more gifted, better fed or better trained than 20 years ago, the peloton as a whole is. The gap between GC leader and domestique must be smaller than it was. This impacts the racing and times up climbs, it is a team sport after all.
  2. Speculation about the latest doping practices without reference to & knowledge of the testing protocols, etc is pretty, well speculative (but not necessarily wrong). This is not my area of expertise, but in areas that I am (was?) knowledgeable I always found the press ill informed, and the internet commentators wildly misinformed (the two are somewhat related).