Ruth Croft was already running as much as 200 kilometres a week and climbing up to 14,000 metres during her build-up to UTMB last year.
And she won.
So as the New Zealander returns to Chamonix this week as defending champion, it poses an intriguing question: how do you improve a training programme that has already delivered the ultimate result?
For Croft and her coach Scott Johnston, the answer isn’t simply to do more.
Instead, the emphasis ahead of her UTMB title defence has been on making an already formidable athlete even more resistant to fatigue – and particularly preparing her legs to withstand the punishing descents late in the race.
‘It can’t be rushed’
Johnston, who also coaches Tom Evans and masterminded a remarkable men’s and women’s UTMB double last year, is now into his fourth season working with Croft.
And despite the enormous numbers involved in her 2025 preparation – typically 180-200km and 10,000-14,000 metres of elevation per week during the build – her overall training volume hasn’t increased significantly.
Speaking to RUN247 as part of a collaboration with TrainingPeaks, Johnston explained: “Ruth’s training volume has not increased much this year.
“What has changed is that we’ve done more strength training, more downhill-specific work and more uphill weighted work.
“This is my fourth year of working with Ruth and we have gradually built her work capacity to the point now where she’s handling significantly more hard training than she was even last year.
“It takes time to build this sort of capacity. It can’t be rushed.”
That distinction is important. Rather than simply adding kilometres to an already huge workload, Johnston has looked at what Croft needs to be able to do late in UTMB when those kilometres and metres of climbing have accumulated in her legs.
Why speed isn’t the problem
Croft hardly lacks speed.
Before establishing herself as one of the world’s leading ultrarunners, she enjoyed considerable success over shorter distances, and Johnston believes developing more of that basic speed offers relatively little return when preparing her for a race as long and mountainous as UTMB.
“Ruth is an exceptional athlete with very good speed,” he explained.
“So for a race like UTMB we’ve not needed to focus much on developing more sustainable speed.
“The primary quality that every ultra runner needs to be improving, even at Ruth’s level, is the ability to resist fatigue in the legs.
“That fatigue is inevitable in any multi-hour event, especially one with as much elevation change as UTMB.”
It’s an idea which also featured heavily in Johnston’s preparation of Evans for Hardrock 100 this summer: in an ultra, the limiting factor is unlikely to be how much blood an athlete’s heart can pump at maximum effort.
The intensity is simply too far below that ceiling for much of the race.
Instead, Johnston argues that local muscular fatigue increasingly becomes the limiting factor. Put much more simply: eventually, your legs get tired and you slow down.
That’s why he sees relatively little benefit in prioritising conventional VO₂-max sessions for an athlete preparing specifically for UTMB.
“While having a high VO₂ max can give an athlete more headroom in their intensity, it is not a guarantee of better performance in endurance sports,” Johnston said.
“In these ultra-long events the average intensity for the athletes is around their first lactate threshold, which is not at all limited by their VO₂ max.
“Efforts in these events are so far below their heart’s maximum pumping capacity that performance is vastly more limited by local muscular fatigue.”
The aim, therefore, is to make the muscles propelling Croft forwards – and upwards and downwards – capable of doing their job for longer before fatigue forces her to slow.
The ‘low-hanging fruit’ after winning UTMB
Finding an obvious weakness in the reigning UTMB champion might sound difficult.
But Johnston did identify one area where he believed there was still significant room for improvement.
“The low-hanging fruit this year for Ruth seemed to be in building that fatigue resistance on the downhill so that she would be strong on both the climbs and descents late in the race,” he explained.
That has produced perhaps the most eye-catching addition to Croft’s training: using ski lifts to help her accumulate more descending.
Once back in France with easy access to lifts, Croft can ride uphill before repeatedly running down, allowing her to place a substantial load on the muscles required for descending without accumulating the corresponding uphill fatigue.
She also incorporates downhill tempo efforts into some long runs.
But there’s an important caveat.
Rather than continually adding more and more downhill load as Croft becomes fitter, Johnston deliberately holds these sessions relatively steady.
“We do not progress the downhill work in our normal fashion like we do the uphill work,” he said.
“We pretty much hold the workload steady on these downhill sessions and just let her gradually adapt to that workload.”
Carry 12kg up – then run back down
The downhill work is only one component of a training programme designed to improve Croft’s durability.
Her key sessions during the final UTMB block include lift-assisted downhill workouts, weighted uphill threshold intervals and weighted uphill/downhill sessions.
And some of those workouts are brutal.
For her muscular-endurance work, Croft has used a pack containing around 12kg of water while climbing roughly 1,000 vertical metres on a gradient of around 20%.
At the top, she can dump the water before descending quickly.
The purpose of carrying the extra weight isn’t simply to make the session harder for the sake of it. Johnston wants to place a greater load on Croft’s leg muscles without requiring a corresponding increase in cardiovascular intensity.
It’s another way of targeting the specific quality he believes will be decisive in the latter stages of UTMB.
“It is the combination of building a base of strength, which we have done more of this year, and then layering more specific muscular endurance work on top of that,” he said.
“This is a process that has gone on since we began the build for UTMB, so every week includes some form of these types of training.”
Comparison with the athlete who won last year
There is another useful reference point available to Johnston this time around: Croft herself.
Her training is logged and analysed through TrainingPeaks, and Johnston can compare this year’s preparation with the build which culminated in victory in Chamonix 12 months ago.
And given what happened last year – not only with Croft but with Evans – there was little incentive to rip up the blueprint.
“Since the build to UTMB last year for both Tom and Ruth was so successful, I didn’t see any need to change much,” Johnston said.
“Having the dashboard and Performance Management Chart in TrainingPeaks is hugely helpful in this process because it allows me to compare the training loads and her fatigue response to last year.”
It’s therefore evolution rather than revolution: using a proven baseline while trying to make targeted improvements where Johnston believes they can produce the greatest return.
An ‘athlete that makes the coach look good’
Of course, there’s another ingredient that is rather harder to reproduce.
Johnston has coached enough world-class endurance athletes to recognise that Croft possesses an unusual ability to absorb training.
“Ruth, like Tom Evans, is the kind of athlete that makes the coach look good,” he joked.
“When a coach has an exceptionally talented athlete, it gives the coach a lot more flexibility in approaches they can take with the training.”
Yet Croft’s capacity for work isn’t simply an ability to suffer regardless of the warning signs.
Johnston points to her understanding of her own body – and the communication between athlete and coach – as a crucial part of why she can sustain such an extraordinary workload.
“Ruth is very good at monitoring how she’s feeling and knows when to back off and let me know that she needs a break,” he explained.
“She and I are in communication every day and discussing how the day’s training went and any changes that need to happen going forward to accommodate her schedule or fatigue.
“Her very high work capacity is a true gift to me as a coach. I almost never hear the words ‘I’m tired’ coming from her.”
Last year’s training was enough to make Croft a UTMB champion.
The challenge this time hasn’t been finding a way to make her train more. It’s been finding the relatively small areas where one of the world’s best ultrarunners can still become better.
And if Johnston’s assessment is right, the difference may become most apparent not when Croft is fresh and climbing strongly early in UTMB, but many hours later – when everyone else’s legs are beginning to say enough.
