Kilian Jornet’s record-breaking UTMB performance this year reminded us he is the greatest trail runner in the world, but what makes him so dominant?

Think of trail running and there is one name that instantly springs to mind. Arguably no one else has dominated a form of running or athletics for as long as Kilian Jornet.

Since winning the first of his four Ultra-Trail du Mont-Blanc (UTMB) titles in 2008, the Catalan has maintained his status as the world’s best on the trails. Whether it’s a vertical kilometre that is over in half an hour or an ultra distance endurance test in excess of 100km, he often seems head and shoulders above the rest.

He has won the SkyRunner world series five times and the Hardrock 100 five times — one of them with his arm in a sling due to a mid-race fall. He has also won the Western States Endurance Run, the USA’s equivalent of the UTMB in terms of status. According to the International Trail Running Association’s database, he has lost only one of his last 14 trail races and four since 2015.

After fifth place in the Sierre-Zinal race in August, it might have seemed as if the 34-year-old’s best years were behind him. However, his record-equalling fourth win this summer in the UTMB, the unofficial world championships of trail running, destroyed that notion. His time of 19 hours 49 minutes 30 seconds was a record for the race, the first time the 170km route had been covered in less than 20 hours.

So what makes him the best trail runner there has ever been, placing him so far out in front of his peers? Is it one thing or a combination of factors? Nurture or nature? The mental or the physical? It is more than likely a culmination of many aspects that combine to create a trail running superman.

At home in the mountains

The son of a mountain guide, Jornet was raised in the Spanish Pyrenees and lived in a mountain hut at 2000m altitude. He would walk for six or seven hours by the time he was 18 months old and climbed a 3000m mountain aged three.

As well as the cardiovascular advantages bestowed by growing up at altitude, his relationship with mountains has also been crucial to his success. He spent much of his life living in the Alps, where he was able to run at 4000m of altitude from his door. When he’s not running in the mountains, he is a record-breaking speed climber and champion ski-mountaineer. The mountains are in his DNA and he is at one with them – a “360° mountain athlete” as he describes himself.

He says 33-40 per cent of his training volume — in other words, up to nine hours per week — takes place at higher than 2000m of altitude.

Derek Dalzell is sports science product marketing manager for Jornet’s sponsor COROS and, as a coach, he has spent much time analysing the athlete’s smartwatch data. 

“When you’re raised a certain way and that’s what’s normal to you, it develops a different skill set that’s second nature to him in terms of climate, in terms of being at that elevation,” says Dalzell.

Skilful descending

Jornet’s phenomenal descending ability is another thing that stands out. Whereas some of us waste energy trying to control our descent on perilous-looking technical ground, his technique means he is able to save the hard work for the ups and recover on the downs.

Stats output from his COROS watch during that record-breaking UTMB win demonstrate this. When chasing the fast-starting Jim Walmsley, he was able to use the downhills to recover from the intense threshold pace of the climbs. Over one 23km segment, Jornet’s heartrate was a remarkably low 119 despite some of that, of course, including uphills.

“The one thing that stands out in his UTMB performance was his ability to recover on the downhills and that, to me, comes back to the specificity of training — essentially being so good at running in technical terrain that he can be running a 16-minute 5km downhill but his heart rate is actually dropping,” adds Dalzell. “If I’m a tactical coach working with Kilian and we know that he recovers on the downhills then you would tell him to push basically tempo or threshold every uphill because you’re going to get your recovery on the downhill.”

Fell runner and mountain guide Paul Aitken, who was one of the pacers during Jornet’s Bob Graham Round record, describes being amazed by the star man’s ability on a notorious section between Great Gable and Green Gable. While another pacer, prolific fell runner Andy Schofield, took a less direct line, Aitken and Jornet took the rough section. Jornet ended up taking a “King of the Mountain” crown for the fastest completion of that section — after around 11 hours of running.

“He was descending ground that most people would have been on their hands and knees on, so I think that’s just an example of how he was eating up rough ground,” says Aitken, adding: “I’m pretty good on downhills, I quite like rough ground. On the [Bob Graham] Round, it was on the descents where the pacers were struggling to keep up with him.

 “When I coach people downhill running and I refer to Kilian, the Salomon hashtag ‘Time to Play’, I think, epitomises his running style. He uses the terrain and the features on the ground in a very playful way, which kind of reduces muscle fatigue because you’re using the terrain to control your feet, slow you down, speed you up. And he really does look like he’s acting for that mindset of the seven-year-old running downhill without fear; that playful mindset that strips away the fear but is also a very effective way of controlling speed.”

Perfect training

In the build-up to this year’s UTMB, Jornet did 76 per cent of his training at an easy pace — described by him as zones one and two or a pace he could maintain for hours. He trained up to 200km (125 miles) per week, much of which was in the mountains.

While he is known for his long days among the slopes, he also does threshold or tempo work and even did four stride sessions over the year, such as 10x100m, to keep the speed.

“The wow factor with Kilian’s data is the elevation per workout,” says Dalzell. “He’s getting 4000-8000ft elevation gain on just his average workouts.”

However, aside from the specifics, Dalzell believes it is his ability to cross-train that makes him so good. 

“In his off-season, when he’s doing his ski-mo, doing a tonne of elevation on cross-country skis, his off-season activities are directly aiding his in-season performance,” he says. “For a lot of athletes it’s tough to replicate that. An off-season plan needs to allow your mind to free up and recover mentally as well. Yes, [Eliud] Kipchoge will get on a bike every now and then or do yoga but not at the level that Kilian is training in these other sports that also enhance his running. An off-season plan needs to allow your mind to free up and recover mentally as well.”

Moving a bit the legs after the long run last week. Nothing better than some scrambling in the backyard. pic.twitter.com/UFqO1ih0Zk

— kilian jornet (@kilianj) September 2, 2022

Mental aspects

Aside from physical attributes, the mental aspect is significant, too. Jornet admitted he was suffering the whole way around the UTMB this year so mental toughness is obviously a factor.

However, in addition to that, Dalzell says his oneness with the mountains means he is able to enjoy his training.

“When I look at athletes like Kilian or Eliud, when you listen to them talk they’re genuinely happy and they love what they do,” says Dalzell. “In order to be motivated to do those hard training sessions you really have to enjoy it. It is who they are, it is what they love to do and it’s a way of life for them.”

Sports scientist and marathon runner John Brewer adds: “Kilian has the mental durability and single-mindedness that enables him to continually train at the highest level, which means that he can focus on pushing himself to extreme limits, even when things are tough. So his success is due to a combination of both ‘nature’ and ‘nurture’ – both have made an essential contribution to his high level of sustained success.”

Built to run

Jornet has a very slight build but it has been noted that his quads and calves are quite big compared to those of a road or track runner. It is that which enables him to power up the hills. His VO2 max has been put between 85 and 92ml/kg/min — the latter would be among the highest ever recorded.

Brewer adds: “To be as good as he is, you have to have the genetic characteristics which predispose you to elite endurance running. These include the potential for a high oxygen uptake capacity, a light but strong physique and plenty of slow-twitch muscle fibres, which are resistant to fatigue.”