A US “ultra-endurance” cyclist has claimed a new world record for fastest woman to circumvent the globe by bike.

Lael Wilcox took 108 days, 12 hours and 12 minutes to cycle 18,125 miles (29,169km), starting and ending in Chicago.

She beat the 2018 record held by Jenny Graham, from Scotland, whose journey took 124 days 11 hours.

Wilcox, 38, of Alaska, set off on 28 May, crossing 21 countries on four continents before arriving back in Chicago around 21:00 local time (02:00 GMT) on Wednesday.

She cycled up to 14 hours a day on her journey, which will now be verified for inclusion in the Guinness Book of World Records.

Experts estimate ultra-endurance cyclists can burn anywhere from 6,000 to 10,000 calories a day on their bikes.

“She just has such incredible physical stamina, mental toughness and just sheer determination to go out and do these extreme efforts,” said Anne-Marije Rook, North America editor at Cycling Weekly magazine.

“It’s just a tremendous effort to be able to do that day in and day out for 108 days straight.”

Wilcox was the first female rider to win the TransAm, a 4,000-mile race across the length of the US. She has also set records in the Tour Divide, a gruelling race traversing the American continental divide along the Rocky Mountains.

While her latest record is billed as a “ride around the world”, Guinness rules only require riders to start and end in the same place, always travelling in the same direction.

A rider’s entire journey, including flights, ferries and public transit, must equal a total distance equivalent to 40,000km – the circumference of the Earth’s equator.

After pushing off from Chicago, Wilcox headed for New York, where she boarded a flight to Portugal.

She then spent several weeks journeying north to Amsterdam, down through Germany, across the Alps, into the Balkans and eventually across Turkey to Georgia.

She then flew to Australia, riding from Perth along the southern coast to Brisbane where she hopped on a flight to New Zealand.

After covering both islands she flew to her hometown of Anchorage, pedalled along the Pacific coast to Los Angeles, then took Route 66 to Chicago.

Graham, the current record-holder, said she had spent the day cheering on Wilcox’s finish: “It’s the most amazing thing to see women out there pushing their sport the way they want to. I’m just a massive fan.”

Rook, of Cycling Weekly, said the efforts of Wilcox and Graham were motivation for others: “What Jenny Graham, Lael Wilcox, and women like them are doing is just pushing the boundaries. Not just in what’s possible in terms of cycling, but the boundaries that have been set on women athletes.”

Wilcox charted her journey with a series of social media videos made with her filmmaker wife, Rugile Kaladyte. The couple have also published a daily podcast, chronicling the daily ups and downs of the trip.

Wilcox’s new record may already be under threat, however. Vedangi Kulkarni, 25-year-old Indian ultra cyclist, is 65 days and roughly 7,700km into her attempt. She too is aiming to complete her ride in 110 days.