Nice story, but Clayton Young will not break the American marathon record in Chicago; finishing will be a challenge

© Copyright – 2026 – Athletics Illustrated

American distance runner Clayton Young is committed to running for the American marathon record on Sunday in Chicago.

The 33-year-old ran 2:08:00 in Chicago in 2023. The course is flat and fast, and numerous records have been set in the Windy City.

But Young is not going to set a new American record in Chicago. In fact, there is a good chance he will not finish the race.

Young is suffering from a 12-centimetre tear in his semimembranosus, a biarticular muscle on the medial, or inner, side of the back of the thigh. It originates at the ischial tuberosity, the sit bone, and inserts into the tibia.

It is not an insignificant muscle for a marathon runner. The semimembranosus helps extend the hip, flex the knee, and stabilize the pelvis and knee during the running gait.

The early stages of the marathon may feel relatively normal. The problem comes later, when fatigue sets in and the demands placed on the hamstring increase. As the race progresses, maintaining pace with a compromised muscle becomes increasingly difficult.

The American record is 2:04:43, set by Conner Mantz at the 2025 Chicago Marathon.

Young has run 2:05:41, but that performance came at the 2026 Boston Marathon, a point-to-point course that does not qualify for record purposes or marathon standards. It therefore cannot be considered his PB in the same sense as a time run on a record-eligible course.

The Boston performance was also aided by a substantial tailwind. Winds were generally 10 to 16 km/h from behind, with gusts reaching 30 to 40 km/h.

Because Boston is a point-to-point course, a favourable wind can provide assistance over much of the entire race rather than being limited to a particular section. It is therefore reasonable to regard Young’s 2:05:41 as a wind-assisted performance rather than an indication that he is currently capable of running 2:05 on a record-eligible course.

Even if we assume the tailwind was worth more than a minute and Young’s equivalent performance in neutral conditions was approximately 2:07:45 to 2:08:00, breaking Mantz’s 2:04:43 American record would still require a substantial jump.

To run 2:04:42, Young needs to average approximately 2:57 per kilometre. When he ran 2:08:00 in Chicago in 2023, he averaged approximately 3:02 per kilometre. This means he would need to run about 4.7 seconds faster every kilometre over the same course.

Compared with his 2:05:41 Boston performance, he would need to improve by about 1.4 seconds per kilometre. If we assume his Boston performance was worth approximately 2:07:45 to 2:08:00 without the tailwind, the gap becomes roughly 3.4/3.5 seconds per kilometre.

No tailwind. Torn hamstring. Faster than ever.

It is not going to happen.

The more likely scenario is that Young gives the record a serious attempt, then steps off the course somewhere around 21 or 22 miles, or roughly 34 to 35 kilometres, once it becomes clear that the record is out of reach and the hamstring is no longer capable of doing the work required or begins to tighten up.

Young’s fastest half marathon came at Houston in 2025, where he ran 1:00:52. That is an indication that, with a healthy hamstring and the right conditions, he is capable of running in the low-2:07 to 2:08 range for the marathon, just as he has.

There is another interesting angle to Sunday’s race.

Young and Mantz have been training partners for years. In the half marathons and marathons in which they have both competed, Mantz has a perfect 8-0 record over Young.

Mantz will be racing the New York City Marathon this year.

Young, meanwhile, has little to lose. He is the underdog; Mantz’s national record is a long shot, and the attempt itself puts his name out there in the public domain, while taking a wild stab at the American record in the build-up to one of the world’s most prominent marathons.

For Young, Sunday may be less about breaking the record than about being part of the conversation.

But the record is not going to leave Chicago with him.

Clayton Young vs. Conner Mantz