American long-distance runner Shalane Flanagan ran the Boston Marathon the day after completing the Chicago Marathon, part of an incredible attempt to run all six Majors in a six-week period.Flanagan retired from competitive running in 2019. Her career included a 10,000 metre silver medal at the Beijing 2008 Olympic Games, and a bronze medal from the 2011 IAAF World Cross Country Championships.The 40-year-old also won the 2017 New York City Marathon, becoming the first American woman to do so since Miki Gorman in 1977.Flanagan is now taking on the incredible feat of completing all six World Marathon Majors in just 43 days. So far, she has completed four, all in under three hours.She started with the Berlin Marathon on September 26th, completing the race in 2 hours 38:32 minutes, before crossing the line at the London Marathon in 2:35:04.After finishing the Chicago Marathon in 2:46:39, Flanagan flew to Boston the next day for her next race. Astonishingly, she managed to run faster, recording a time of 2:40:34.

Flanagan has two more races to go before completing the challenge. She is set to run the Tokyo Marathon as a virtual event in Oregon on October 17th, before taking part in the New York City Marathon on November 7th.

Social media users have applauded Flanagan for completing back-to-back marathons after ESPNw shared news of the achievement on Twitter.

"I knew she was doing this and I saw her in the Chicago Marathon when I was downtown," one Twitter user wrote. "But the real shocker is how she dropped a whole 6 minutes off her Chicago Marathon is insane."

Another posted: "She improved her time at the Boston Marathon?! That just insane. This lady had endurance for days… literally."

Wheelchair racer Tatyana McFadden has also been acknowledged after finishing on the podium of both the Chicago and Boston Marathon.

One day after winning the women’s wheelchair division at the Chicago Marathon, she placed second in Boston. McFadden, an eight-time Paralympic champion, also finished second at the Berlin Marathon and third in London.

The 32-year-old is also set to compete at the New York City Marathon next month. She will be joined by rival Manuela Schär, another athlete aiming to finish five majors this year.