Why marathon world records keep falling, and what the rules allow

On October 8, 2023, Kelvin Kiptum ran 2:00:35 at the Chicago Marathon, taking 34 seconds off the 2:01:09 that Eliud Kipchoge had set in Berlin a year earlier. On the same course a year later, Ruth Chepngetich ran 2:09:56 and became the first woman under 2:10, almost two minutes faster than the previous record. Two of the oldest marks in distance running moved by margins that would once have taken a decade.

The explanation usually offered is shoes, and shoes are part of it. But the governing body's regulations and race reports describe several factors working together: courses chosen to remove elevation, footwear the rules now define to the millimetre, pacing that takes decision-making off the athlete, and a ratification system with its own fine print.

Flat courses and the geography of fast

Both current records were set on big-city courses chosen for their profile. Berlin, where Kipchoge set the previous men's mark, describes its 42.195 km route as the flattest of the Abbott World Marathon Majors with very little elevation gain, and the organisers list 15 aid stations, with carbohydrate drink available at 9, 15, 20, 25, 30 and 36 km and gel at 27.5 km. A course with predictable, frequent stations lets athletes rehearse exactly when they will fuel.

The splits from the two men's records show how the course is used. In Berlin on September 25, 2022, Kipchoge passed 5 km in 14:14 and halfway in 59:50, then held on through a slower second half. In Chicago thirteen months later, Kiptum went through halfway in 1:00:48, almost a minute slower than Kipchoge had, and then ran the 30 to 35 km segment in 13:51 and the 30 to 40 km stretch in 27:52, according to the World Athletics ratification release. A negative split of that size is only possible on a course that offers nothing to slow a runner late in the race.

Chepngetich's record followed the same template on the same streets. World Athletics' race report from October 13, 2024 records 15:00 at 5 km, 30:14 at 10 km, 1:04:16 at halfway and 1:31:49 at 30 km, on the way to 2:09:56 against Tigist Assefa's previous mark of 2:11:53.

Shoes: what World Athletics actually permits

The rules are more specific than the public conversation about "super shoes" suggests. The current Athletic Shoe Regulations, approved by the World Athletics Council on March 19, 2026 and in force from April 20, 2026, set the maximum sole thickness for road running events at 40 mm and for track events, jumps and the javelin at 20 mm. The regulations state that from November 1, 2024 any shoe with a sole above the table's limits is no longer approved for World Rankings competitions.

The measurement itself is defined in detail. Thickness is taken at the centre of the forefoot, at 75 percent of the shoe's internal length, and at the centre of the heel, at 12 percent, with the shoe placed on a hard flat substrate. The approval process uses a standard sample with a 270 mm sole, which is US 8.5, EUR 42 or UK 8, and a 5 percent tolerance (2 mm on a 40 mm shoe) applies when a shoe is sent for investigation. A non-spike shoe may contain no more than one rigid structure, which may run the full length of the sole or part of it but must not be stacked, looped or overlapping, and no shoe may contain embedded sensing technology.

Two further conditions shape what elites can race in. An Available Shoe must be purchasable through the manufacturer's sales channels, including pre-order periods, before the athlete first wears it in a ranked competition, and World Athletics may ask the manufacturer for evidence. A Development Shoe, one never offered for sale, can be worn for a maximum of 12 months from its listing, and never at World Athletics Series events or the Olympic Games. The practical effect is that a record shoe must be a product, not a one-off, and the earlier piece on how carbon plate shoes changed distance racing covers how manufacturers responded.

The four percent study and what it measured

The number that follows these shoes around comes from a 2018 paper in Sports Medicine by Wouter Hoogkamer, Shalaya Kipp, Jesse Frank, Emily Farina, Geng Luo and Rodger Kram, titled "A Comparison of the Energetic Cost of Running in Marathon Racing Shoes." Eighteen high-calibre athletes ran six five-minute trials, three shoe models twice each, at 14, 16 and 18 km/h, while the researchers measured oxygen uptake and carbon dioxide production during minutes three to five.

The prototype shoe, which combined a highly compliant, resilient midsole with a stiff embedded plate, lowered the energetic cost of running in all 18 subjects. Averaged across the three speeds, cost was 4.16 percent and 4.01 percent lower than in the two established marathon racing shoes used for comparison, with shoe mass matched, and the saving did not change with speed. The authors predicted that top athletes could run substantially faster in such shoes and achieve the first sub-two-hour marathon.

That figure is a reduction in energy cost on a treadmill over five minutes, not a four percent cut in finishing time, and the records that followed came on courses and with pacing that the laboratory did not model.

Pacing: humans in front, lights on the rail

On the road, pacing still means people. The ratification release for Kiptum's record describes him breaking from a seven-strong lead group that included Daniel Mateiko, dropping Mateiko after 30 km, leading by 49 seconds at 35 km and winning by almost three and a half minutes. Chepngetich's race report records Ethiopia's Sutume Asefa Kebede running alongside her early. The value of a group is partly aerodynamic and partly psychological: the athlete does not have to judge pace alone until the final third.

On the track, the pacing has become electronic. When Jessica Hull broke the 2000 m world record with 5:19.70 at the Monaco Diamond League on July 12, 2024, the World Athletics race report described trackside lights indicating record pace that "never left her side," with pacemakers taking her through 1000 m in 2:39.88 before she ran alone. Her own account was that "I was just looking at the lights, hoping they wouldn't catch me."

Both arrangements remove a cognitive task, so the runner can spend attention on form and fuelling rather than arithmetic. The official race reports for the current marathon records describe human pacing only.

Ratification, mixed races and the fine print

A time is not a record until the governing body says so. Kiptum's 2:00:35 was ratified in a press release dated February 6, 2024, four months after the race. Chepngetich's mark appears in the December 11, 2024 ratification announcement as "Women's marathon 2:09:56 (mx)," the notation World Athletics applies to a women's mark set in a race with men on the course. Readers comparing women's records should check for that tag, because a women-only race is a different event in the record books.

The fine print can also move after the fact. On October 23, 2025, the Athletics Integrity Unit announced a three-year ban for Chepngetich after she admitted anti-doping rule violations involving the diuretic hydrochlorothiazide, from a sample collected on March 14, 2025. AIU head Brett Clothier stated that "all Chepng'etich's achievements and records pre-dating the 14 March 2025 sample stand," while noting that the unit would continue to examine material recovered from her phone. The record is therefore intact as this is written, with an investigation still open.

That sequence shows why the record pages carry dates and notations rather than just times.

The useful way to read the next record headline is to ask four questions in order. Was the course one of the flat, big-city routes where the current marks were set? Was the shoe an Available Shoe under the 40 mm rule, or a Development Shoe on its 12-month allowance? Was the race mixed, and does the mark carry the (mx) tag? And has the governing body ratified it, which can take several months?

None of those questions diminishes the performance. They explain why the marathon is now faster than its own history predicted, and why the record books, read carefully, tell you how each mark was made.