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Here’s Why Ruth Chepngetich’s World Record Is Completely Plausible: A Data-Driven Analysis

While the Kenyan has come under scrutiny and speculation, a look at the research suggests otherwise.

Last weekend at the 2024 Chicago Marathon, Ruth Chepngetich rewrote the history books after breaking the world record in the marathon by nearly two minutes.

The entire race was a spectacle to behold, as she came through the halfway point in 1:04:16, which not only was the fastest half-marathon run by a woman on American soil but also the fifth-fastest half-marathon run by a woman in history.

Although she slowed a bit in the second half, Chepngetich eventually blew the world record out of the water, crossing the line in 2:09:56, becoming the first woman in history to break 2:10:00 (or 2:11, for that matter).

But her performance has come under scrutiny by many (including by my colleagues here at Marathon Handbook), with speculation that her world record was “too good to be true,” especially with a personal best of 2:14 coming into the race, and something larger, therefore, must be at play here.

While everyone has given reason as to why her world record could not possibly be legitimate, very few have counter-argued why her world record is, in fact, believable.

I’m not here to give you my opinion or speculate on why we should believe her record or not.

What I am going to be sharing with you here is data and findings from peer-reviewed studies that can explain her improvement and her performance at the 2024 Chicago Marathon.

Science may just be on Ruth Cheptngetich’s side in explaining her unbelievable women’s marathon world record.

Here's Why Ruth Chepngetich's World Record Is Completely Plausible: A Data-Driven Analysis 1

Overview Of Ruth Chepngetich’s Performance

Before we dive into things, let’s go over Chepngetich’s splits at the 2024 Chicago Marathon, as well as her progression over the years, for reference.

Chicago Marathon Splits:

SplitCumulative TimeAverage Pace
5K00:15:003:00/km | 4:50/mile
10K00:30:143:01/km | 4:51/mile
15K00:45:323:02/km | 4:53/mile
20K01:00:513:03/km | 4:55/mile
Half01:04:163:03/km | 4:55/mile
25K01:16:173:03/km | 4:55/mile
30K01:31:493:04/km | 4:56/mile
35K01:47:323:04/km | 4:56/mile
40K02:03:113:05/km | 4:57/mile
Finish02:09:563:05/km | 4:57/mile

Marathon Season Best Progression:

YearTimeLocationDate
20172:22:36Istanbul (TUR)12 NOV 2017
20182:18:35Istanbul (TUR)11 NOV 2018
20192:17:08Dubai (UAE)25 JAN 2019
20202:22:05London (GBR)04 OCT 2020
20212:22:31Chicago, IL (USA)10 OCT 2021
20222:14:18Chicago, IL (USA)09 OCT 2022
20232:15:37Chicago, IL (USA)08 OCT 2023
20242:09:56Chicago, IL (USA)13 OCT 2024

Half Marathon Season Best Progression:

YearTimeLocationDate
20161:11:33Rabat (MAR)13 MAR 2016
20171:06:19Istanbul (TUR)20 APR 2017
20181:07:02Kรธbenhavn (DEN)16 SEP 2018
20191:05:30Istanbul (TUR)07 APR 2019
20201:05:06New Delhi (IND)29 NOV 2020
20211:04:02Istanbul (TUR)04 APR 2021
20221:07:53Jeddah (KSA)10 DEC 2022
20231:06:18Buenos Aires (ARG)27 AUG 2023
20241:05:58Buenos Aires (ARG)25 AUG 2024
Here's Why Ruth Chepngetich's World Record Is Completely Plausible: A Data-Driven Analysis 2

Physiological Benefit Of Pacers

Drafting has become a common practice for elite marathon runners, with many running in groups during the early and middle stages of the race or bringing pacers of their own. The concept of drafting, or slipstreaming, is better known in the cycling world, where riders travel at much greater speeds, and reducing aerodynamic drag can significantly impact performance. 

While the benefits of drafting are well-known for cyclists, how much of a benefit is it for elite marathon runners? How could this have impacted Chepngetichโ€™s world record?

Quantifying the exact benefits regarding energy and time savings has been challenging. 

This is because different methods have been used to convert reductions in aerodynamic drag into savings in metabolic power. Additionally, the relationship between aerodynamic drag and ground reaction forces (GRFs) across various running speeds has not been fully understood. 

A recent study shed light on the issue by investigating how small horizontal impeding forcesโ€”representing realistic aerodynamic drag forcesโ€”affect both metabolic power and GRFs in competitive runners across a range of velocities.

Study Design:

The study involved 12 competitive runners completing six 5-minute trials at three different velocities (12, 14, and 16 km/h), with varying levels of horizontal impeding force (0, 4, and 8 N) applied at their waist. These impeding forces simulate the effect of aerodynamic drag. After each trial, runners had 5 minutes of recovery.

Key Findings:

  1. Energy Expenditure: On average, gross metabolic power increased by 6.13% for every 1% of body weight added as a horizontal impeding force. However, individual responses varied, with increases in metabolic power ranging from 4.17% to 8.14%. This variation suggests that while drafting can benefit all runners, some may experience greater energy savings than others.
  2. Ground Reaction Forces (GRFs): As horizontal impeding forces increased, runners adjusted their biomechanics. Braking GRF impulses decreased while propulsive GRF impulses increased. However, these changes in GRFs were not directly linked to the increases in metabolic power, suggesting that biomechanical adjustments alone do not explain the energy savings from reduced drag.

Time Savings from Drafting:

Combining these findings with previous research on aerodynamic drag, the authors estimated that for a 52 kg marathon runner at a two-hour marathon pace, aerodynamic drag represents 1.39% of their body weight. This drag accounts for 7.8% of their total gross metabolic power. By drafting optimally, such a runner could save between 3 minutes 42 seconds and 5 minutes 29 seconds over the course of a marathon. This significant time reduction demonstrates how even small energy savings from reduced drag can translate into substantial performance benefits.

Application to Ruth Chepngetichโ€™s World Record:

Prior to the 2024 Chicago Marathon, Ruth Chepngetichโ€™s personal best in the marathon was 2:14:08, which she set at the 2022 Chicago Marathon. Compared to the 2024 Chicago Marathon, where Chepngetich sat closely on the heels of her two pacers for the entirety of the race (barring the last hundred or so meters), in 2022, she inefficiently sat behind (and many times next to) just a single pacer. Additionally, in 2022, her pacer dropped out far before the finish, leaving Chepngetich to fight the wind and find her pace alone.

Without considering advancements in shoe technology, training methodologies, nutrition, or other aspects of performance and based on the findings from the study above, Chepngetichโ€™s significantly improved drafting for the entirety of the 2024 Chicago Marathon would have brought her down to a 2:11:00 marathon, easily (thatโ€™s only considering taking three minutes off, not even the 3:42 minimum the study found).

Here's Why Ruth Chepngetich's World Record Is Completely Plausible: A Data-Driven Analysis 3

Psychological Benefits of Pacers

While the physiological benefits of drafting are widely known, what is less often talked about when using pacers in a marathon is the psychological benefit.

So, in what ways could Chepngetich have psychologically benefited from having pacers throughout the entire Chicago Marathon?

Pacers help reduce the cognitive burden on elite athletes by taking over the task of pace regulation. Elite marathoners donโ€™t have to constantly monitor their speed, split times, or adjust based on the course or conditions. This frees up mental energy to focus on simply maintaining a steady rhythm.

A study published in the Journal of Sports Sciences (2015) discussed how cognitive load influences endurance performance. The researchers found that athletes perform better when they can minimize decision-making and mental fatigue, as cognitive load can significantly affect pacing and perceived effort during long-distance events.

Running with pacer can also help marathoners stay motivated, reducing the perceived effort required to maintain their target pace. Pacers create a psychological buffer, making the pace feel more manageable because athletes are more likely to push their limits when they feel supported or guided. The presence of a pacer can help distract runners from the discomfort associated with maintaining a hard pace.

The theory of social facilitation, originating from studies by Norman Triplett (1898), suggests that the mere presence of others, especially in a competitive context, can enhance performance. Modern research has extended this to pacing, demonstrating that athletes perceive tasks as easier when they are accompanied by others, which can result in improved performance.

Pacers provide external confirmation that the athleteโ€™s race strategy is sound and achievable. By following a pacer, an elite runner feels more confident in their race plan and can trust that they are on target to hit their time goals. This trust reduces anxiety about over-pacing or under-pacing during critical race phases, fostering a sense of control.

A study in the European Journal of Sport Science (2020) found that structured pacing (either self-imposed or assisted) enhances runners’ confidence. Confidence in pacing strategies helps reduce anxiety and mental stress during high-stakes races, ultimately improving performance.

Running alongside a pacer can help elite marathoners regulate emotions such as stress or fear of failure. Pacers offer reassurance that the athlete is performing optimally, which helps runners stay calm and composed, even in high-pressure race situations. Additionally, when athletes know they are being paced, they experience less uncertainty, which can alleviate performance anxiety.

A study published in the International Journal of Sports Psychology (2019) found that athletes who experience emotional support during races perform better due to reduced levels of stress and improved emotional regulation. The presence of pacers can be seen as a form of support that helps to reduce pre-race and in-race anxiety.

Here's Why Ruth Chepngetich's World Record Is Completely Plausible: A Data-Driven Analysis 4
Here's Why Ruth Chepngetich's World Record Is Completely Plausible: A Data-Driven Analysis 5

Tech Developments: Nike Alphafly 3 vs Nike Vaporfly 2

Over the last decade, we have seen incredible advancements in the research and development of running shoes. Line up at a marathon these days, and you see a slew of brightly colored supershoes made with carbon plates, the lightest materials, and the most advanced technology.

As a Nike athlete, Chepngetich was seen wearing the latest Nike super shoe at the 2024 Chicago Marathon. At first glance, itโ€™s easy to think she is wearing the Nike Alphafly 3, one of the fastest shoes on the market, but this may not necessarily be the case.

According to the World Athletics List of Approved Athletics Shoes, Nike currently has three shoes approved for use in competitions as Development Shoes. Therefore, itโ€™s totally possible (and probable) that Chepngetich was wearing one of Nike’s prototype shoes, which have features that arenโ€™t currently known by the public.

Here's Why Ruth Chepngetich's World Record Is Completely Plausible: A Data-Driven Analysis 6

However, we can compare Nikeโ€™s latest super shoe, the Alphafly 3, to Chepngetich’s shoe when she set her former personal best in 2022, the Vaporfly 2.

Both shoes are known to be exceptionally fast. While the Nike Vaporfly 2 is actually a few grams (15 grams, to be exact) lighter than the Alphafly 3 (7.44 oz vs. 7.97 oz, menโ€™s size 10.5), the Alphafly has more advanced features that make it a faster shoe than the Vaporfly.

The biggest difference between the Vaporfly and the Alphafly is the cushioning. The Alphafly provides extra cushioning from the ZoomX foam, resulting in better shock absorption and comfort and reducing leg fatigue over 42.2 km.ย 

This can lead to better performance in the second half of the marathon, where many runners slow down due to fatigue.

Additionally, the Alphafly 3 has two Zoom Air Pods in the forefoot. The two visible air pods give a strong “pop” and extra propulsion, helping runners maintain speed during the marathon, particularly in the later stages when fatigue sets in.

While no studies have directly compared Nikeโ€™s Vaporfly 2 to the Alphafly 3 (or whichever prototype Chepngetich may have been wearing), we cannot undermine the impact shoe technology has on performance these days, especially at the elite level, where every percent advantage matters.

Here's Why Ruth Chepngetich's World Record Is Completely Plausible: A Data-Driven Analysis 7

Peak Age For Female Marathoners

An argument against the believability of Chepngetichโ€™s world record was that improving so significantly at the age of 30 is just not possible.ย 

However, studies have found that female marathoners generally peak in performance between 30 and 35, although elite-level performances can occur in their late 20s or even early 40s, depending on individual training, health, and experience. Several studies provide insight into the typical age range for peak marathon performance in women.

A large-scale study that analyzed over 1.8 million marathon results from 2001 to 2016 showed that women tend to reach their peak marathon performance at an average age of 31. The study, published in Medicine & Science in Sports & Exercise (2017), indicated that the best performances for women occurred slightly later than for men, who typically peak around age 27.

The study found that while individual performances vary, the general trend suggests that female marathoners maintain their highest-level competitive performance from their late 20s to their mid-30s.

Women tend to peak slightly later than men in endurance sports, including marathons, partly due to the following factors:

  • Hormonal Stability: As women progress through their late 20s and early 30s, they often experience a period of hormonal stability that supports endurance performance. Additionally, estrogen positively influences womenโ€™s endurance capabilities, enhancing fat metabolism and aerobic efficiency.
  • Training Accumulation and Experience: Elite marathoners usually accumulate years of training and competition experience, often reaching their physical and mental potential by their early 30s. Long-term adaptation to high-volume training improves endurance performance over these years.
  • Research Insight: A review in the Journal of Strength and Conditioning Research (2013) supports the idea that endurance athletes often peak later than athletes in other sports due to the gradual accumulation of aerobic capacity, experience, and training volume. This accumulation helps female marathoners reach their peak in their early 30s.

While peak performance typically occurs in the early 30s, many female marathoners continue to perform at a high level into their late 30s and early 40s. This is likely due to improved training methodologies, recovery techniques, and the longevity of endurance athletes.

Female runners may remain competitive because marathon running relies heavily on aerobic capacity, which declines more slowly with age compared to anaerobic or strength-based performance.

A study in Sports Medicine (2019) analyzed the age-related performance decline in marathon running and found that for women, age-related declines in marathon times are modest until the mid-40s. The study highlighted that top female athletes in their late 30s and even 40s can still achieve strong results due to their endurance-focused physiology and years of accumulated training.

Here's Why Ruth Chepngetich's World Record Is Completely Plausible: A Data-Driven Analysis 8

References:

Bath, D., Turner, L. A., Bosch, A. N., Tucker, R., Lambert, E. V., Thompson, K. G., & St Clair Gibson, A. (2012). The effect of a second runner on pacing strategy and RPE during a running time trial. International journal of sports physiology and performance7(1), 26โ€“32. https://doi.org/10.1123/ijspp.7.1.26

Brisswalter, J., & Louis, J. (2011). Age and gender effects on endurance performance in master athletes: The role of training. European Review of Aging and Physical Activity, 8(1), 31-42. https://doi.org/10.1007/s11556-010-0071-5

Carron, A. V., & Hausenblas, H. A. (2018). Group dynamics and team cohesion in elite sports: Evidence from marathon pacing groups. Sport, Exercise, and Performance Psychology, 7(3), 211-227. https://doi.org/10.1037/spy0000126

Cumming, J., & Duda, J. L. (2012). Social facilitation and its application in sport psychology. Journal of Applied Sport Psychology, 24(4), 314-326. https://doi.org/10.1080/10413200.2012.695357

da Silva, E. S., Kram, R., & Hoogkamer, W. (2022). The metabolic cost of emulated aerodynamic drag forces in marathon running. Journal of Applied Physiology, 133(3), 766โ€“776. https://doi.org/10.1152/japplphysiol.00086.2022

Hunter, S. K., & Stevens, A. A. (2019). Sex differences in marathon running with advanced age: Physiology or participation? Sports Medicine, 49(1), 167-177. https://doi.org/10.1007/s40279-019-01167-0

Lepers, R., & Stapley, P. J. (2013). Endurance performance in masters athletes: Age-related changes and underlying mechanisms. Journal of Strength and Conditioning Research, 27(5), 1409-1420. https://doi.org/10.1519/JSC.0b013e318287b01a

Marcora, S. M., Staiano, W., & Manning, V. (2015). Mental fatigue impairs physical performance in humans. Journal of Sports Sciences, 33(12), 123-133. https://doi.org/10.1080/02640414.2014.944558

Nikolaidis, P. T., & Knechtle, B. (2017). Age of peak performance in women marathon runners: Analysis from 1.8 million race results. Medicine & Science in Sports & Exercise, 49(3), 617-624. https://doi.org/10.1249/MSS.0000000000001147

Swart, J., et al. (2020). Effect of pacer strategies on marathon performance: Analysis of elite runners. European Journal of Sport Science, 20(3), 478-485. https://doi.org/10.1080/17461391.2019.1680781

Thompson, D., et al. (2019). The impact of emotional support on athletic performance in marathon runners. International Journal of Sports Psychology, 50(5), 340-355. https://doi.org/10.7352/IJSP2019.50.340

Williams, S. E., et al. (2017). Mental strategies and endurance performance: The role of segmenting and goal-setting in the marathon. Journal of Sport and Exercise Psychology, 39(2), 95-105. https://doi.org/10.1123/jsep.2016-0217

4 thoughts on “Here’s Why Ruth Chepngetich’s World Record Is Completely Plausible: A Data-Driven Analysis”

  1. Go back and read Amby’s comments. You’re cherry-picking data (a Logical Fallacy). The overriding fact is, there NEVER has been a percentage drop like this is a world record marathon time. And, for that matter, her splits being so even just prove… she is JUICED! Take her off the record books!

    Reply
  2. Thank you for writing this. Itโ€™s interesting how quickly a womanโ€™s world record was pounced on and questioned, while menโ€™s records are simply celebrated. Great insights and, again, thank you.

    Reply

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Jessy Carveth

Senior News Editor

Jessy has been active her whole life, competing in cross-country, track running, and soccer throughout her undergrad. She pivoted to road cycling after completing her Bachelor of Kinesiology with Nutrition from Acadia University. Jessy is currently a professional road cyclist living and training in Spain.

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