When the world’s best cyclists make the impossible look routine, where does extraordinary human physiology end and our understanding of it begin?
I’ve been following professional cycling for roughly ten years now. I’ve watched some incredible performances, witnessed rivalries unfold over three weeks of racing and developed an appreciation for just how demanding this sport really is.
I’m also a recreational cyclist. I ride indoors on Zwift, get out on the road when I can, and occasionally convince myself that I’m stronger than I actually am. Usually, the next climb brings me back to reality.
Perhaps that’s why watching the likes of Chris Froome and Tadej Pogačar has become so fascinating to me.
It’s not simply that they win. It’s how they win.
Watching Froome relentlessly grind his rivals into submission on a mountain pass, or Pogačar launch an attack when everyone else is already at their physical limit, makes me wonder what kind of human physiology makes these efforts possible.
I’m not writing this to accuse anyone of doping. Cycling has had more than enough of that conversation, and I don’t believe extraordinary performances should automatically be treated as evidence of cheating.
But I do think there’s a fascinating scientific question worth asking.
Just how far can the human body actually be pushed?
The Chris Froome era: when marginal gains seemed to change everything
When I started following professional cycling more closely, Team Sky was approaching the height of its dominance.
Chris Froome won four Tours de France between 2013 and 2017, along with the 2017 Vuelta a España and 2018 Giro d’Italia.
Team Sky’s approach seemed almost clinical.
Their riders would line up at the front of the peloton, set a punishing tempo on the climbs, and gradually dismantle the opposition. By the time Froome made his move, often there was nobody left capable of responding.
It wasn’t always the most exciting racing to watch, but it was extraordinarily effective.
And naturally, people asked questions.
Professional cycling was still dealing with the fallout from the Lance Armstrong era. Suspicion was deeply embedded in the sport’s culture, and a team dominating the Tour de France inevitably attracted scrutiny.
What interests me most about Froome, though, isn’t the controversy. It’s the physiology.
In 2015, Froome underwent testing at the GSK Human Performance Lab in London.
His measured VO₂max was 84.6 mL/kg/min. Adjusted mathematically to his reported Tour de France racing weight, it would have been approximately 88.2, assuming his absolute oxygen uptake remained unchanged.
His reported sustained power during laboratory testing was approximately 419 watts, corresponding to roughly 6.25 watts per kilogram at his racing weight.
To put that into perspective, producing 419 watts for twenty minutes is already an extremely demanding effort for a trained amateur cyclist.
Froome’s physiology allowed him to sustain enormous workloads while competing against some of the best endurance athletes on the planet.
And importantly, his test results also showed something else.
His underlying physiological capacity had been exceptional years before he started winning the Tour de France.
There was a real engine there.
Source: Chris Froome’s physiological testing results, Cyclingnews, December 2015
Then along came Tadej Pogačar
If Froome represented precision, discipline and relentless efficiency, Pogačar represents something rather different.
He seems capable of doing almost everything.
He can win a Grand Tour, dominate mountain stages, attack from ridiculous distances and then turn around and win a one-day Classic.
By 2026, he had won five Tours de France, two elite road World Championships and numerous major one-day races.
What I find remarkable isn’t simply his ability to accelerate away from other professional cyclists.
It’s his ability to do it after hours of racing.
Think about that for a moment.
These riders aren’t lining up fresh at the bottom of a climb to perform a twenty-minute FTP test.
They’ve already spent hours riding, often at speeds and intensities that would be challenging for most reasonably fit recreational cyclists to maintain for even a fraction of the time.
They’ve climbed mountains, responded to attacks, dealt with changing weather conditions and accumulated enormous amounts of muscular fatigue.
And then, somehow, Pogačar accelerates.
Not against average riders, but against athletes who have dedicated their entire professional lives to becoming extraordinarily efficient endurance machines.
It’s genuinely difficult to comprehend.
Let’s talk about watts
For those who don’t cycle with a power meter, a watt is simply a measure of how much mechanical power a rider produces.
The more watts you’re generating, the more work you’re doing.
But when climbing, absolute power is only part of the equation. Your weight matters enormously.
That’s where watts per kilogram, or W/kg, comes in.
Consider a hypothetical 65 kg cyclist:
| Power output | Watts per kilogram |
|---|---|
| 260 watts | 4.0 W/kg |
| 325 watts | 5.0 W/kg |
| 390 watts | 6.0 W/kg |
| 455 watts | 7.0 W/kg |
Now imagine sustaining 455 watts for close to forty minutes.
That’s not a sprint. That’s an immense continuous aerobic effort.
And imagine doing it near the end of a long mountain stage, after several hours of racing, with the pressure of the Tour de France hanging over your shoulders.
That’s the kind of performance that has scientists paying attention.
A 2025 paper by Norwegian researcher Ole Kristian Berg examined six of Pogačar’s major Tour de France climbs during 2024 and 2025.
Using publicly available climbing times, rider characteristics and mechanical modelling, the study estimated average power of approximately 442 ± 15 watts over efforts lasting around forty minutes, with an inferred VO₂max likely exceeding 90 mL/kg/min.
These weren’t readings taken directly from Pogačar’s power meter. They were scientific estimates based on the physics of the performances.
That’s an important distinction.
Nevertheless, the numbers were extraordinary.
How much oxygen can a human body actually process?
This is where things become especially interesting.
VO₂max measures the maximum amount of oxygen your body can utilise during intense exercise, relative to body mass.
Think of it as one measure of the size of your aerobic engine.
A reasonably healthy adult might have a VO₂max somewhere around 35–45 mL/kg/min, depending on age, sex and fitness.
Well-trained endurance athletes can reach substantially higher levels.
Elite professional cyclists can exceed 70 or 80, and exceptional endurance athletes have been measured in the 90s.
But VO₂max alone doesn’t determine performance.
Two athletes with identical VO₂max values can produce very different amounts of power.
One important reason is gross efficiency — how effectively the body converts metabolic energy into mechanical work at the pedals.
If your body requires less oxygen to generate a given wattage, you can potentially sustain more power from the same aerobic capacity.
Consider our hypothetical 65 kg rider generating 455 watts.
At 25% gross efficiency, the metabolic cost of that effort is approximately 1,820 watts. Using a representative oxygen energy equivalent, that would require around 87 mL/kg/min of oxygen uptake at the workload.
At 23% efficiency, the requirement is closer to 95 mL/kg/min.
The rider’s maximum oxygen uptake would have to exceed whatever rate they were actually sustaining, unless other energy systems contributed to the effort.
That small change in efficiency makes a remarkable difference to the implied physiological demands.
And this helps explain why researchers can disagree about Pogačar’s numbers.
In 2026, Quentin Leplat published a reanalysis that revised assumptions about aerodynamics, rider mass, drafting and metabolic efficiency.
The resulting model suggested a required VO₂max of approximately 100.7 ± 3 mL/kg/min for the performances examined.
That figure is beyond the upper range of reliably documented human measurements.
But here’s the critical point: it is a modelled requirement, not Pogačar’s measured VO₂max.
A model can reveal that our understanding or assumptions are being challenged. It cannot, by itself, establish an athlete’s actual physiology or explain how the performance was achieved.
Source: Reanalysis of Power-Based VO₂max Estimation in Tadej Pogačar, Journal of Science and Cycling, 2026
Perhaps the real superpower isn’t maximum power
The more I read about elite cycling physiology, the more I’ve started to think that focusing entirely on FTP and VO₂max misses something important.
Durability.
In cycling, durability describes how well an athlete preserves their ability to produce power after accumulating fatigue.
Suppose two riders can both produce 450 watts for twenty minutes when completely fresh.
On paper, they appear similarly capable.
Now imagine they’ve each completed five hours of hard racing.
One rider has lost 10% of that ability and can now manage 405 watts.
The other has lost only 2% and can still produce 441 watts.
That’s a 36-watt difference.
On a sustained mountain climb, it’s enormous.
Suddenly, what looks like an impossible late-race attack becomes easier to understand.
It’s not necessarily that one cyclist has dramatically more peak power.
It’s that one cyclist retains much more of their available performance after everyone else has started fading.
This, to me, might be one of the most important scientific explanations for what we’re witnessing in modern professional cycling.
It also changes how I think about training as an amateur.
We spend so much time discussing FTP, maximum power and personal records. Perhaps we should spend more time thinking about how well we maintain that power after several hours in the saddle.
Modern cycling isn’t the same sport it was twenty years ago
Another factor that deserves recognition is just how much professional cycling has evolved.
Nutrition alone has changed dramatically.
Today, elite cyclists can consume well over 100 grams of carbohydrate per hour during demanding races, using carefully designed carbohydrate mixtures and gastrointestinal training.
Compare that with the fuelling practices of previous generations, and there’s a meaningful difference in how much energy riders can supply during prolonged competition.
Add improvements in aerodynamic equipment, tyres, drivetrain efficiency, altitude training, heat adaptation, recovery strategies and workload monitoring.
None of those developments individually explains everything.
But combined, they can produce significant performance gains.
And perhaps most importantly, teams now have far better information about how individual athletes respond to training.
Rather than simply training harder, the emphasis is increasingly on training more precisely.
That doesn’t eliminate the limits of human physiology. But it may help exceptional athletes get closer to those limits more consistently.
Of course, there’s the elephant in the room
You cannot discuss extraordinary professional cycling performances without acknowledging the sport’s history.
Cycling has endured major doping scandals, including the Festina affair, the Lance Armstrong era and numerous subsequent cases.
Team Sky also faced serious scrutiny over its medical practices, and Froome was involved in a salbutamol investigation that was ultimately closed without an anti-doping rule violation being established.
These are reasons why fans are sometimes sceptical.
I understand that scepticism.
But I also believe there’s a danger in allowing history to rob us of the ability to appreciate exceptional athletes.
A rider producing extraordinary power is not evidence, by itself, of prohibited performance enhancement.
Equally, passing anti-doping tests doesn’t provide absolute proof that no prohibited practice has ever occurred.
Both statements can be true.
Science should investigate extraordinary performances. Anti-doping authorities should remain vigilant. Teams should be as transparent as reasonably possible.
And fans should be able to ask difficult questions without automatically accusing anyone of cheating.
I don’t believe those positions are contradictory.
The more I understand, the more extraordinary it becomes
Perhaps the most interesting thing about studying the physiology behind professional cycling is that it hasn’t made these performances seem less remarkable.
It’s actually done the opposite.
When I watch Pogačar attack on a mountain, I now think about the oxygen his body must be processing, the carbohydrates being oxidised, the metabolic efficiency required and the fatigue he’s already accumulated.
When I revisit Froome’s performances, I think about the enormous aerobic engine required to sustain that kind of climbing power.
And when I return to my own bicycle, I have a renewed appreciation for how brutally difficult sustained effort really is.
We sometimes describe these professional cyclists as superhuman.
They’re not.
They’re human beings with extraordinary physiological characteristics, supported by decades of accumulated sports science and increasingly sophisticated training systems.
There may still be aspects of their performances that science cannot fully explain with the information currently available.
To me, that isn’t a reason to jump immediately to accusations.
It’s a reason to keep asking questions.
Where exactly are the limits of human endurance? How close are these athletes to those limits? And how much further can science, training and natural human ability take us?
I don’t have definitive answers.
But as someone who loves cycling, those questions make the sport even more fascinating to watch.
And perhaps that’s enough.
Because sometimes, the most extraordinary thing about professional cycling isn’t that these riders make the impossible look easy.
It’s that understanding how difficult it really is makes their achievements even harder to believe.
This article is a personal reflection on endurance physiology and professional cycling. References to power outputs and oxygen consumption distinguish laboratory measurements from estimates derived from publicly available racing data. Nothing in this article alleges wrongdoing by Chris Froome, Tadej Pogačar or their respective teams.
