A source close to Cragg said her withdrawal is the result of adrenal fatigue as a result of the Epstein-Barr virus.

What happened in the 2016 Olympic marathons where several athletes including Eliud Kipchoge and American stars Galen Rupp and Shalane Flanagan were given secret shoes, made to look like other shoes on the market, that scientists believe produce 2% gains in performance was "mechanical doping." Will World Athletics acknowledge this fact and potentially invalidate the 2016 Rio Olympic men's marathon results?

From Jordan Hasay (50%) to Stephanie Bruce (5%), we break down the odds for the  contenders at the 2020 US Olympic Trials.

Kosgei comes in as the defending champion after winning in 2018 in 2:18:35 and then winning London in 2:18:20. She is joined by Betsy Saina (2:22:56) and Mexico's Madai Perez (2:22:59). Chumba won Chicago in 2015, but will only be the fourth fastest in the field as Dubai champ Getaneh Molla (2:03:34) and runner-up Herpasa Negasa (2:03:40) lead the way along with previously announced Mo Farah. USA's Amy Cragg, Chris Derrick and Brogan Austin have all withdrawn.

The 5th fastest American in history thinks she can still PR at age 35. She also reveals that that she thinks the Nike Zoom Vaporfly 4% shoes have helped her a lot.

We break down what it all means as we we get closer to the 2020 US Trials. Plus, why we think Berlin might be a better option. *MB: 2019 Chicago Marathon US field is out: Cragg, Derrick, Ritz Join Rupp & Hasay

Another top names announced include US marathon champs Brogan Austin and Emma Bates as well as Stephanie Bruce, Lindsay Flanagan, Chris Derrick, Diego Estrada and Parker Stinson.

Many me be surprised that Cragg, who hasn't run a marathon sine running 2:21:42 in Tokyo in February of 2018, isn't doing a Spring marathon.

Cragg ran 43:23 (5:25 pace) to win the "one-time test event" to win the women's race easily while Austin ran 38:07 (4:46 pace) to beat out Jared Ward (38:17) and Parker Stinson (38:25). Both winners commented on how tough and hilly the course was.

The women's race at 2019 USA XC looks INCREDIBLE. For the 1st time in US history, three sub-14:50 women will race each other as Shelby Houlihan, Shannon Rowbury, and Molly Huddle are all racing as are World Championship medalists Courtney Frerichs and Amy Cragg, plus the most recent NCAA XC champ to turn pro in Karissa Schweizer, a 2016 Olympian in Marielle Hall and MUCH MORE. The men's race includes 5 Olympians plus Ben True and the pro xc debut for Drew Hunter. *MB: USA World XC Trials Saturday; Top Entrants and Weather Forecast

2018 was the best year in the history of the women's marathoning. Coming into the year, only five women in history had ever broken 2:19 but six different women did it 2019.  Plus 11 times a woman broke 2:20 in 2018, the most in history.

With Cragg, Thweatt and Jordan Hasay, organizers say this is the deepest American women's field in Chicago history.

The Japanese Corporate Track and Field Federation’s “Project Exceed” was offering 100 million yen ($936,000) to any man who could break the 2:06:16 national record. Shitara did it with a legendary run, mowing down the field after he was dropped at 32k.

Tokyo may not have cachet of London or Boston but it's by far the best marathon for US fans to watch as it's on during prime time in the US. We get you ready for Saturday night's race.

Shalane Flanagan cracks the top 5 as we for the first time exclude from our rankings an athlete, Sarah Chepchirchir, not convicted of a doping offense.

2017 is almost over and it's time to look back at the year that was in running. We reflect on the most exciting races of 2017, including history from Emma Coburn and Courtney Frerichs, major marathon wins from Shalane Flanagan and Galen Rupp, the brilliance of Eliud Kipchoge and much more.