Zach Bitter

He said that in middle school he found winning the 1,600 meters far more fun than finishing last in the 100-meter dash, and that through high school and college he learned endurance training and found he got better as distances grew longer.⁠[1]

At the University of Wisconsin–Stevens Point he ran for the men’s cross country team from 2005 to 2007 and for the track and field team in 2007.⁠[2]

He said he switched to a high-fat, low-carbohydrate diet in late 2011 as he moved into ultramarathons, after experimenting with regimens such as Atkins, and that he has since recovered better and raced faster.⁠[3]

At Desert Solstice in Phoenix in December 2013 he set the American track record for 100 miles, and organizers said he also set a 12-hour world record; UltraRunning magazine named it the Outstanding Male Performance of the Year.⁠[4]

In April 2014 he won the U.S. 100K championship at the Mad City 100K in Madison in 6:44:03, qualifying for the 100K world road championships in Doha; he was then a high school teacher in Madison.⁠[4]

In 2015 he won a national road championship at 50 miles in 5:17:25, and he had represented Team USA at the world championships.⁠[2]

At Desert Solstice in December 2015 he ran 402.5 laps of a 400-meter track to set an American track record of 11:40:55 for 100 miles, averaging 7:01 per mile, and won $600.⁠[5]

In his race report he wrote that researching the history of track ultras led him to Don Ritchie, who held the 100-mile world best for 25 years, and he recalled his training in Madison, including tempo runs after a full day of teaching.⁠[6]

He led the 2016 Javelina Jundred 100-mile race from the start and won in 13:30:28, more than an hour ahead of runner-up Brett Sanborn.⁠[7]

He explained that in low-volume periods carbohydrates make up about 5% of his calories, rising to 20–30% in peak training blocks, while fat always remains the majority.⁠[1]

On March 23, 2018, the Human Performance Outliers Podcast, which he co-hosts with Shawn Baker, released its first episode, exploring the outer limits of performance through interviews and Q&As on nutrition and performance.⁠[8]

He won the Tunnel Hill 100 in Vienna, Illinois, in 12:08:36, a 100-mile trail world record 24 minutes faster than Jonas Buud’s 2010 mark, after covering the first 50 miles in 5:42.⁠[9]

The time also cut 36 minutes from Ian Sharman’s 2011 American record, earning him USA Track & Field Athlete of the Week.⁠[10]

At Six Days in the Dome at the Pettit National Ice Center in Milwaukee he set a men’s 100-mile world record with an unofficial time of 11:19:13; he said it had been a six-year journey with numerous failed attempts.⁠[11]

He broke the 11:28:03 record held by Russia’s Oleg Kharitonov, the equivalent of four consecutive sub-three-hour marathons, then kept going to cover 104.88 miles in the 12-hour event, breaking his own 12-hour record.⁠[12]

A Manitowoc, Wisconsin, native, he was then an endurance athlete and coach living in Phoenix, Arizona; his record pace averaged 6 minutes 48 seconds per mile.⁠[13]

With Ultra London and other races cancelled because of the coronavirus pandemic, he turned to the 100-mile treadmill record at home; his longest previous treadmill run had been 30 miles.⁠[14]

Running from 6:30 a.m. until just after 6:30 p.m., he set the 100-mile treadmill world record, beating Canadian Dave Proctor’s 12:32:26 by more than 20 minutes.⁠[15]

At Desert Solstice in Phoenix he attempted Yiannis Kouros’s 24-hour world record of 303.5 kilometers but covered only 186 kilometers; Nick Coury won the race.⁠[16]

He appeared on episode 205 of the Lex FridmanLex FridmanLex Fridman is a Soviet-born, US-raised computer scientist and podcast host who works as an MIT research scientist on human-AI interaction and autonomous driving. His Lex Fridman Podcast is known for hours-long conversations with guests including heads of state and technology leaders.Open the full entry Podcast, whose description calls him an ultramarathon runner and coach; topics included the marathon mentality and the psychology of quitting, the 100-mile world record, training and race strategy, the MAF 180 formula, his diet philosophy and fasted training, the treadmill record and shoe technology.⁠[17]

At the 2021 Tunnel Hill 100 he led most of the day but was caught by Phil Young at mile 97 and finished second in 12:47, about three minutes behind the winner.⁠[18]

As of October 2026 his website lists him as the American record holder at 100 miles (11:19:13) and 12 hours (104.88 miles), with four national championships and wins at races including the San Diego 100, Javelina 100 and Ice Age 50; he shares training and nutrition strategies through personalized coaching, training plans and the Human Performance Outliers Podcast.⁠[19]

Personal website: Public link: https://zachbitter.com/ (opens in a new window)⁠[17]

X: Public account: https://x.com/zbitter (opens in a new window)⁠[17]