Cycling races can be won in a myriad of ways, but the winners generally have one thing in common – they are less fatigued than the rider in second place. Whether it’s a bunch sprint for the line or a solo breakaway who escapes the pursuit of the peloton, their race-winning move saw them churn out a power output that belied the kilometres already in their legs and one that their closest competitors simply couldn’t match.

This ability has set certain riders apart throughout the history of road cycling, and is what differentiates the likes of Mathieu van der Poel from the rest when it comes to dominating at Paris-Roubaix or Tadej Pogačar’s superhuman displays deep into the third week of a Grand Tour.

Speaking to GCN, Van der Poel’s coach Kristof De Kegel said that while the Dutchman isn’t even the best in the Alpecin-Premier Tech team when it comes to power output in a fresh state, it’s his ability to deliver that same output “after 3,500 minimum to 4,000-5,000 kilojoules in a Monument” that is probably his biggest advantage. 

While genetics are likely to play a role, sports scientists are now trying to measure this fatigue resistance, and unlock a way of targetting it – and improving it – in training.

A fourth dimension

Historically, performance has been determined by factors such as VO2 Max, lactate threshold and economy – the oxygen cost of a specific power output – and it has been possible to fairly accurately predict an athlete’s current potential based on these metrics. 

“Around 1991, Michael Joyner presented a model of endurance performance,” says Toby Helder, lead performance clinic physiologist at St Mary’s University and sport scientist at Orreco. “That model essentially had a bunch of different factors that you could improve that might predict performance.”

All of these tests however are undertaken when an athlete is fresh. While useful markers for setting training zones, each will reduce over the duration of a race as the body starts to fatigue. “A few papers looking at cyclists have found that things such as critical power have been reduced after a few hours of cycling, which is understandable – no one can hold power forever,” says Helder. But he adds that research has shown that some seem to have better resilience than others.

It’s this reduction in capacity – and its cause – that has been the focus of intense research over the last five years. “I know some of the top teams are trying to figure out how to measure it best because if you can find out what makes someone's performance metrics reduced, you can try and prevent that,” he says.

A measurement minefield

Currently, there is no agreed-upon way to test a rider’s fatigue resistance or how to quantify it with a number like that for lactate thresholds or VO2 Max. 

“No one's quite figured out what is the best simulation of how to induce fatigue,” says Helder. While some research focuses on performance after a set amount of work (kilojoules) or time, he explains that a review from 2025 found that “no one seems to have a right way to do it because no one quite knows what they're targeting for” but that any tests had to be conducted after at least 90 minutes of fatiguing exercise.

Helder adds that while there isn’t a clear testing protocol yet, the studies have indicated that durability is linked more to intensity rather than solely duration. “It seems to be that the amount of time you are in each different zone – moderate, heavy, severe – seems to accumulate. It's a bit like you're burning your matches. You only have so many matches that you can have in your back pocket, and the more you burn them, the less you can use later on. It seems to be intensities that are burning it more than the duration.”

Fighting fatigue

The amount of matches a rider has is partially down to genetic makeup and DNA, while training history and volume are factors in fatigue resistance. But there are signs that certain sources of fatigue can be slowed, helping to add matches to the box or stop them from being lit in the first place.

“There seems to be a few different ways that people are breaking down over time,” says Helder, who suggests that how well you can recruit muscles neuromuscularly, the ability to process high amounts of carbohydrates for long durations, and a break down in form and loss of efficiency (both physiologically and mechanically) are all common causes.

But each of these can be targetted and improved upon in training, aiding a rider’s durability. “We already know that if you're taking enough carbohydrates, it seems to improve fatigue resistance in some way, which is why these guys are loading up so much,” says Helder. “That's also where things such as strength training have been looked at more – if you can become stronger then, in theory, you'll break down less likely over time.”

A top-end differentiator

While a fatigue resistance score isn’t likely to pop up on the likes of TrainingPeaks in the immediate future, Helder believes that it does have potential to be the next big thing in performance metrics.

“In theory, if we could find a reliable and valid way to measure this fatiguing metric, it is exciting,” he says, adding that it could be a way of identifying “what is it that brings out the Pogačars in the peloton?”

But don’t expect it to be a topic of conversation on the local club run like FTP numbers and watts per kilo. “It’s the differentiator at the top end. Amateurs are not going to be spending that much time on a bike and their drop off might be a lot larger just because they've not got that training background in them.”

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