In our sport, it’s not often you see an elite athlete declare a lofty goal months in advance. In many cases, fans don’t even know a track athlete’s competition schedule, let alone their aspirations for the season. For Josh Kerr to announce his intent to break the world record in the mile—arguably the most iconic distance—and share the journey along the way, was a pivotal moment in the running community. It got people talking, debating, and celebrating.
More than anything, Kerr’s bold, unabashed approach throughout the training cycle was much-needed inspiration.
This story was written in partnership with Amazfit.
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In a culture that often awards shortcuts, the 1500-meter world champion dedicated himself to the goal by maximizing every training element to elevate his approach. To lower his previous mile personal best of 3:45.34, Kerr became meticulous with data metrics—tracking his sleep, recovery, and heart rate variability (HRV) using Amazfit wearable technology. The information gathered from his Helio Ring and Cheetah 2 Pro watch enabled Kerr and his coach, Danny Mackey to make informed decisions that helped him avoid overtraining.
After receiving his sleep data, Kerr even installed a bedroom altitude chamber and unique system to pump excess oxygen into his home gym—allowing the three-time global medalist to reap the benefits of living and training in three different altitude environments from his home in Albuquerque, New Mexico.
The precision ultimately paid off at the London Diamond League meet on July 18. In a thrilling showdown between Kerr, a stacked field, and the clock, the Olympic silver medalist met the moment head on.
With the help of Brooks Beasts teammate Brannon Kidder and second pacer Zan Rudolf, the 28-year-old Scot embraced the world record pace he’d practiced countless times. Powering through the first 400 meters in 55.3 seconds, Kerr appeared calm and controlled behind the rabbits guiding him at London Stadium.
In the early moments of the race, Kerr’s heart rate quickly rose from about 120 beats per minute (bpm) on the start line to 160, and hit a max heart rate of 188 about 400 meters into the race. By the first 800 meters—which he clocked in 1:51.1—Kerr remained in the 180 bpm range as he settled into an aggressive, but rhythmic pace.
When officials rang the bell with one lap to go—sending the British crowd into a frenzy—Kerr remained up front with American Yared Nuguse running a few steps behind him. On the backstretch, Kerr shifted gears—pushing far ahead of Nuguse and just slightly beyond the pace of the previous world record (3:43.13) run by the legendary Hicham El Gerrouj in 1999.
On the homestretch, Kerr glided through lane 1 with no challengers—emerging as the fastest miler in history. When the clock read 3:42.66 as he flew across the finish line, Kerr threw his arms up in celebration—a singular moment when diligence and courage paid off in a big way.
After the race, the Diamond League champion shared how achieving a flow state, which he’d practiced many times ahead of the attempt, helped him do something unprecedented in front of a home crowd.
“My two pacemakers set the tone, the river. They set the stream, and all I had to do was sit in that water for as long as I could, follow it, and not fight it,” Kerr said. “I wasn't on a chase today, I was flowing with the conditions that were set, and I just needed to not slow down. I had a blast out there.”
Overall, Kerr ran an incredibly even race and accelerated at the perfect time over the four-lap distance. His 400-meter splits were 55.3, 55.8, 55.4, and 54.9 seconds with pacemakers taking him through 1,000 meters. His final 200 meters was covered in 27.4 seconds—his fastest split of the day. In comparison, El Guerrouj had pacers through 1200 meters and averaged 55.5 seconds for each 400-meter split. The Moroccan was famously pushed to the finish line by runner-up Noah Ngeny on the bell lap when he set the previous record 27 years ago in Rome.
According to the data experts at Amazfit, Kerr’s metrics indicate the middle-distance runner’s form and efficiency operated closer to that of a sprinter when compared to those in the standard population. He hit a max stride length of 2.2 meters and hovered around 200 milliseconds for his ground contact time, while elite sprinters can hit up to 2.7 meters in stride length and have a low ground contact time of about 100 milliseconds.
Below are some of the key data metrics behind Kerr’s record-setting run:
Max heart rate | 188 bpm |
Average heart rate | 178 bpm |
Start line heart rate | 123 |
Max cadence | 200 |
Max power | 500 |
200-meter splits | 27.5, 27.8, 27.9, 27.9, 27.7, 27.7, 27.5, 27.4 |
400-meter splits | 55.3, 55.8, 55.4, 54.9 |
Max stride length | 2.2 meters (7.25 feet) |
There’s likely even more to come for the world record-holder. Reflecting on his athlete’s historic performance, Mackey said he believes Kerr can lower the mark with additional pacing.
“If there could be help for 1200 meters, he could run a little bit faster, so we set up for that 41 Finish just to set the bar high,” Mackey said. “That’s what Josh wanted to do, and I feel like he could’ve done it.”
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