Josh Kerr Shares His Plan to Break the Mile World Record.

Josh Kerr wants to run a mile faster than any human ever has. To get there, the Scottish middle-distance runner has stopped leaving his bedroom for anything other than sleep and a movie with his wife.

In April, Kerr and his wife Larimar converted their bedroom in Albuquerque into an altitude chamber. The city already sits at roughly 5,250 feet above sea level. The chamber adds another 3,000 feet, putting Kerr at a simulated 8,000-plus feet for about half of every day. He spends 12 hours in the room in total — about eight overnight, and another two-hour block combined with an afternoon nap.

The setup, described by Kerr in a first-person account published by The Telegraph on June 30, is part of a broader plan pointed at one thing: taking down the mile world record of 3 minutes 43.13 seconds, which has stood since 1999.

“I do not compare my training to others,” Kerr wrote. “I judge myself on how I peak for my goals, what my team thinks, and what we have spent 15 years fine-tuning to get to this mile world-record attempt.”

Living at altitude, then living higher

The physiology behind altitude training is well established. Time spent at elevation prompts the body to produce more oxygen-carrying red blood cells, which can improve endurance performance at sea level. Kerr has been based in Albuquerque for years to take advantage of that effect. The bedroom chamber is an attempt to push it further without the cost of a training camp.

His daily rhythm now revolves around the room. He and Larimar, a dermatologist at a nearby hospital, head into the chamber around 7:45 p.m. They are usually asleep by 8:30. Larimar leaves for work at 5:45 a.m. Kerr returns to the chamber between roughly 2 and 4 p.m. for a nap before she gets home.

He sleeps around nine hours a night. Recovery, he said, is the part of training most runners underrate.

A workout that told him the record is possible

Kerr trains under coach Danny Mackey and follows what Mackey calls a “funnel periodisation” model — the volume and character of his hard sessions narrow toward a peak race. Kerr runs hard on Tuesdays, Fridays and Sundays, keeps Monday, Wednesday and Thursday for recovery running of seven to 10 miles, and takes Saturdays off from running.

The session that gave him the most confidence in his world-record fitness came recently on the track: four repetitions of 800 meters. The first two were paced at 1:59. The next two were meant to break world-record mile pace. He ran them in 1:50.51 and 1:49.9.

“It was a huge confidence boost to know that I can turn over faster than world record pace even at high altitude, with three lots of 800m already in my legs,” Kerr wrote in The Telegraph.

His Tuesday and Sunday runs cover about 16 miles, much of it at tempo effort, which he described as a six or seven out of 10. The track work happens on Fridays. All-out efforts — the 10-out-of-10 kind — are rare.

“When it comes to those 10/10 efforts, falling over, producing huge amounts of lactic acid, it is probably once every couple of months,” he wrote.

The gym, the physio, the sacrifice

Kerr did not want to be in a weight room until about five years ago. Now he lifts for up to 90 minutes on Tuesdays and Fridays, within a few hours of his hardest running sessions. He adds plyometrics on Thursdays. The reasoning, he said, is partly biomechanical — fatigued muscle fibers recruit more motor units — and partly practical, because it protects his easy days from added load.

The strength work is periodised across six phases in the year, and includes power cleans, heavy squats, jump squats and push presses. Injury prevention drives a large part of it.

Recovery is heavily staffed. Kerr sees a physio three or four times a week. His mother is a physiotherapist. He also works with a chiropractor and with Sarah Bair-Cross, Brooks’ athletic trainer, who has been on his team since 2015 and carries a portable massage table so she can treat him at the track.

The lifestyle cost is real, and Kerr did not sugarcoat it. He grew up in Edinburgh and still has family in the U.K.

“The hardest sacrifice is not being with family in the UK, not seeing nephews grow up or not spending more time with my grandparents,” he wrote. “You do miss things such as birthdays and weddings.”

Kerr’s mile record attempt follows years of pointed buildup. His account makes clear the physiology is in place; whether it converts into a sub-3:43.13 remains the open question every miler in his position faces. Kerr, who took world 1500m gold in 2023, offered a short summary.

“I feel on track,” he wrote.