American ultra and mountain runner Hillary Gerardi has set a new women's fastest known time for an ascent and descent of Mont Blanc (4,809) on foot in 7 hours 25 minutes and 28 seconds. The previous record was held by Swedish athlete Emilie Forsberg, who set a time of 7 hours 53 minutes and 12 seconds on June 21, 2018.

The route begins and ends at the Saint Bernard du Mont-Blanc Parish church in the centre of Chamonix and combines street, forest trail and alpine high-mountain terrain. 

Gerardi, who is based in Chamonix, had been preparing for this record attempt, which she described on Instagram as being 'years in the making', by spending more time on technical terrain in the high mountains than on the trails.

Hillary's route differed slightly from Emilie's previous record-setting run on the Grands Mulets route. Due to the risk of serac collapse, Hillary chose to ascend and descend via the steeper, more technical but less exposed North Ridge of the Dome du Goûter and the Bosses Ridge.

Writing on Instagram, she said:

'Yesterday was the best possible outcome I could have imagined for this project that has been years in the making! The preparation has been physical, mental, technical, relational, material, altitudinal, meteorological and climatological…

It has allowed me to spend many days in the mountains and countless hours scheming and planning both alone and with friends. It has been both a solo pursuit I've been focused on and also a shared goal that so many people have contributed to. I've made new friends through the process and felt my awe and respect for the mountains grow at the same time that my understanding of myself also expanded.'

Hillary planned the logistics of clothing and equipment choice for the mixed terrain meticulously. Speaking to Trails Endurance Media after her feat, Hillary explained in French that she left the church in trail running gear, including a running vest, which she then swapped for a 15-litre pre-deposited backpack at around 1,400 metres of ascent, and that she had worn a harness preemptively throughout the trail section.

The bag included extra clothing, micro-spikes, steel crampons, an ice axe, a helmet with headtorch and a crevasse rescue kit. Hillary met Valentine Fabre - an accomplished ski-mountaineer, with whom Hillary set an FKT for a ski traverse of the Haute Route last year - at La Jonction and the pair roped-up to traverse the glaciated terrain below Mont Blanc's North face safely. 

Hillary described the assortment of layers that she wore on the upper section, including a t-shirt, trousers, a long-sleeved top, a fleece, a down jacket and a windproof jacket. On her return to the forest section during the descent, Hillary removed these outer layers and swapped cramponed footwear for trail running shoes.

Although weather and mountain conditions aligned on the day, Hillary added that it was very windy high on the arête.

The men's fastest known time for the Mont Blanc speed challenge on foot was set by Catalan mountain runner Kilian Jornet on 11 July 2013 in 4 hours, 57 minutes and 40 seconds. 

Hillary adds this FKT to a long list of course records and ultrarunning and mountain running wins, which includes victories in the 120km Grand Raid des Pyrénées in 2015, the 32km Salomon Glen Coe Skyline in 2018, the 90km Marathon du Mont Blanc in 2021 and the 52k Trofeo Kima skyrace in 2022.