Josh Kerr’s Record Spike Was Built to Work at Only One Pace

Josh Kerr broke the mile world record on Saturday in a shoe that was never designed to do anything else. Brooks spent five months building the Hyperion 222 for one runner at one speed, a project its senior director of product development, Danny Orr, described to Popular Science the day before the race. Kerr’s 3:42.66 at the London Diamond League took 0.47 seconds off Hicham El Guerrouj’s 27-year-old mark and remains subject to standard ratification. The spike had cleared World Athletics approval days earlier.

World Athletics has capped every track spike at a stack height of 20 millimeters since Nov. 1, 2024, under regulations that also restrict shoes to a single rigid plate, and a world record shoe gets no exemption. “There are height measurements at 12 percent and 75 percent along the midsole that have to be below a 20-millimeter height,” Orr told Popular Science. Every brand designs against the same ceiling, so Brooks looked for its advantage in specificity, building the spike from eight years of testing on Kerr, whom it has sponsored since 2018: high-speed video, pressure readings, and VO2 data.

Geometry That Only Works at 16 mph

A 3:42.66 mile averages just over 16 mph (26 km/h), four laps at roughly 55 seconds each. At that speed Kerr lands on his mid-foot and rolls immediately onto his forefoot, and the sole’s pronounced curve, which Orr calls “a little bit shaped like the bottom of your bicycle tire,” is drawn for that contact pattern alone. The same curve fights a slower runner’s heel-first landing. “You would almost feel like you were running uphill in the spike,” Orr said, whereas Kerr at race pace gets the opposite sensation: “it’s almost like he’s running slightly downhill.”

The carbon fiber plate inside is the stiffest Brooks has ever made, and it was calibrated to Kerr personally. Using finite element analysis, an engineering stress simulation, Brooks matched the plate’s stiffness to the force Kerr generates against the track, because Kerr is bigger and stronger than most milers. “His ability to generate force is higher than a lot of other people that we would work with in this space,” Orr said. “The spike is much stiffer than anything that we’ve ever made before.”

The outsole holds permanent titanium pins, unavailable on any retail spike per Brooks, set among 222 carbon fiber traction elements, matching the 222-second target of Project 222, which Kerr announced in March. In details released before the race and published by FloTrack, Brooks said the upper was formed on a last taken from Kerr’s foot and wrapped with a TPU band it calls the Victory Band; the sockliner reads “The Pursuit.” “We’ve never utilized any of these materials in a track spike to date,” Orr said.

A Suit Cut to One Body

The suit followed the same logic. Brooks worked from 3D body scans of Kerr, and the result is sleeveless and high-necked, nearly seamless, closed by an ordinary front zipper, a detail Kerr asked for. Forecasts put race-day temperatures around 76 F (24 C), warmer than record chasers usually want, and the lower half is dotted with laser-cut perforations that let heat escape while the fabric stays tight to the body.

Brooks’ promotional videos describe the suit as completely silent, and Orr framed that as psychology rather than aerodynamics. Kerr races best in a flow state, Orr told Popular Science, and “a big part of the conversations with him on the apparel side is what are some of these elements that can just remove the noise.” “The last lap was incredible,” Kerr said afterward in comments published by World Athletics. “I was deaf in the last 110 metres.”

Why This Record Can Stand

When Faith Kipyegon attacked the four-minute mile at Nike’s Breaking4 event in June 2025, her 4:06.42 was never eligible for ratification: the exhibition used male pacers, and Nike had not submitted her prototype spike to World Athletics for approval. Brooks took the opposite route. Competing prototypes went to an independent testing lab in Colorado, the results were replicated in Albuquerque, and the final build reached the governing body’s approved list days before the race.

The mark also came out of a real race: Kerr beat runner-up Yared Nuguse, who ran 3:45.69, by just over three seconds in the Emsley Carr Mile. His buildup included a 2:42.45 1,200m time trial, the fastest ever run.

Kerr trains in the Hyperion 222 only on his hardest days, because the geometry resists anything slower, and Brooks plans a public version that Orr says will be “very, very limited.” “This shoe is step one on our plan for LA ’28,” Orr said of the 2028 Los Angeles Olympics. “This is iteration one, and we’re going to make changes to this in iteration two and three.”