How Conner Mantz Ran 2:04:43: Inside the American Marathon Record

How Conner Mantz Ran 2:04:43: Inside the American Marathon Record

The Conner Mantz Series · Part 1 of 3

In October 2025, Conner Mantz ran 2:04:43 at the Chicago Marathon and broke a 23-year-old American record. Most runners would call that the race of their life. Conner calls it something else:

"I consider that like a solid B performance."CONNER MANTZ

This week he lines up at the New York City Marathon. Before he does, here's how he ran the fastest marathon ever by an American, the workouts that got him there, and what every marathoner can take from it.

2:04:43 American record Chicago 2025
4th Place in a world-class field
55 sec Off the old record 2:05:38, set in 2002
4:45 Per mile for 26.2 miles
Conner Mantz racing in a USA singlet

1How the Record Race Unfolded

Conner Mantz racing for Team USA

The plan was bigger than the record. Conner was aiming to break 2:04, with a 62:00 halfway target.

"When I went for it, the plan was actually to break 2:04. But then our pace was kind of all over the place. And so when we saw sub-2:04 wasn't going to happen, it was like, well, let's just make sure sub-2:05 happens."CONNER MANTZ

The record run

His first four 5Ks

Bars start at zero. Shorter bar = faster. Red = fastest.

0-5 km14:234:38/mi
5-10 km14:574:49/mi
10-15 km14:444:45/mi
15-20 km14:564:48/mi
62:19First half
62:24Second half
2:04:43American record

Splits via LetsRun.

He went out in 4:30 for the first mile with a tailwind and ran his fastest 5K first, then deliberately backed off. He reached halfway in 62:19, and his second half (62:24) was almost exactly the same. Late in the race he fought back onto a pack, caught Geoffrey Kamworor around mile 25, and was outsprinted for 3rd by just 6 seconds.

2Why He Calls It a "Solid B"

Conner Mantz portrait

Conner believes knowing the record was safe made him stop racing in the final miles.

"I almost think like knowing I was going to get the American record had me become less competitive in actual racing portions of it."CONNER MANTZ
"I wasn't thinking about like beating the guys as much as I was thinking of, well, as long as I don't run like 5:20s, I'm going to break the American record."CONNER MANTZ
"I don't think I've finished a marathon and felt as fresh as I did afterward."CONNER MANTZ
The takeaway Have an A goal and a B goal before race day. When plan A slipped, Conner switched to plan B without panicking, and still broke the record.

3"The Marathon Really Doesn't Start Till 20 Miles"

Conner Mantz running in the rain

Watching other Americans chase his record at Chicago this year, Conner kept one rule in mind:

"...there's probably 15 guys in the US who could be on pace through 30K and not do it... we all like to overestimate our fitness and 30K to 20 miles is about when the marathon really starts."CONNER MANTZ
Learn moreHow to run the first 20 miles so you can race the last 10KAlmost every runner feels good at 30K. What separates a great marathon from a bad one is what's left for the last 10K. Conner's record run is the model: a near-even split, with the halves just 5 seconds apart.•Bank energy, not time. Going out too fast costs you more late than it gains you early•Check in at 30K, don't celebrate. Ask: can I hold this, or speed up, for 10 more km?•Have a B goal ready for when plan A slips, like Conner did•Keep fueling all the way through. Late-race fade is often an empty tank, not a lack of fitness

Pace it like Conner. Tap your goal time for even 5K splits:

Sub-2:30 marathonEven pacing for 2:30 · tap to open
Each 5 km17:46
Per km3:33
Per mile5:43
Halfway1:15:00
Sub-3:00 marathonEven pacing for 3:00 · tap to open
Each 5 km21:20
Per km4:16
Per mile6:52
Halfway1:30:00
Sub-3:30 marathonEven pacing for 3:30 · tap to open
Each 5 km24:53
Per km4:59
Per mile8:01
Halfway1:45:00
Sub-4:00 marathonEven pacing for 4:00 · tap to open
Each 5 km28:26
Per km5:41
Per mile9:09
Halfway2:00:00

Train like an American record holder

More miles. Less pounding.

Conner runs two of his runs each week on LEVER. Find out why in Part 2 and Part 3 of this series.

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4The Sessions Behind the Record

Conner Mantz training

In the months before Chicago, Conner's build included a few signature markers. These come from his pre-race interviews:

13 x 3 milesConner's session · about a month out
Splits13:39, 13:42 and 13:40
PaceAbout 4:33 per mile
WhereProvo, around 4,500 ft
WhySustained work faster than goal marathon pace
2The long marathon-pace runConner's session · August, with Clayton Young
Start3 miles at about 4:43 per mile
Then8 miles at about 4:39-4:40 per mile
TotalAbout 11 miles of work
WhyLong, steady running right around race pace
3A race as a fitness checkConner's session · U.S. 20K Championships, September
Result56:16, an American record
TimingAbout six weeks before Chicago
WhyHe called it his best sign of fitness for the marathon
Steal itHow to use these sessions at your levelYou don't need 4:33 pace. The structure is what matters. Use your own goal marathon pace (from the pacing cards above):•3 x 3 miles at a bit faster than marathon pace, with 2-3 minutes easy between, about 4-6 weeks out•Long marathon-pace run: 2-3 miles slightly slower than goal pace, then 6-8 miles at goal pace•Tune-up race (10K to half marathon) 4-6 weeks out, to check your fitness honestly•Keep the easy days easy between them, so the hard sessions stay hard

He also trained at altitude, moving to Park City (about 7,000 ft) while doing his hard sessions lower down in Provo.

5How He Fuels 26.2 Miles

Conner Mantz running

Fueling is one of the most practical lessons from Conner's marathons, and he treats it like training.

"...minimum is 80 and maximum is probably 110... So 80 is like the minimum, but I'm probably closer to, I don't know, probably closer to a hundred."CONNER MANTZ, ON GRAMS OF CARBS PER HOUR
Workouts Bottle at Tuesday and Thursday sessions Mostly before, with a bit more during as the race gets closer.
Long runs Race-day amounts on Saturdays He matches what he'll take in the marathon, by the mile.
Final weeks Before every run Including his treadmill doubles, so his body is used to it.
Learn moreFueling 101 for your marathonYour muscles store enough carbohydrate for roughly 90 minutes of hard running. After that, what you take in during the race decides how well you finish. Pros like Conner take in a lot, but they practiced to get there.•Start lower and build. Many runners begin around 40-60 g of carbs per hour and work up in training•Practice on long runs and workouts, not for the first time on race day•Use the same products you'll use in the race•Spread it out every 15-20 minutes instead of all at once

General guidance, not individual nutrition advice. Talk to a sports dietitian for your own plan.

6Will Someone Break It?

This October, a pack of Americans went after his record in Chicago. The closest, Clayton Young, finished 40 seconds back. Conner's take:

"I think because so many people went for it this last time, I think it kind of showed people like 2:04 isn't just easy."CONNER MANTZ
"...I think if going into the Olympic trials, if someone's in 2:04:40 shape, they're going to make the team."CONNER MANTZ

7What Every Marathoner Can Learn From Conner

Pace for the last 10K His halves were 5 seconds apart. Even pacing beats a fast start.
Have a plan B When sub-2:04 slipped, he switched goals and still made history.
Practice your fueling He trains his gut at workouts, long runs and even easy doubles.
Respect recovery Feeling great after a marathon doesn't mean you're recovered. That's Part 2.

Next in the series

Part 2: Two stress fractures, 170 days off, and how LEVER helped him come back

He felt so good after the record that he went straight back to training. It cost him Boston.

More miles. Faster recovery. Fewer setbacks.

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