🏃‍♂️ The Marathon Revolution: From Kiptum to Chepng'etich - What's Fuelling the Fastest Era in Distance Running?

How Sport Science is Witnessing the Rewriting of Human Endurance Limits

Kelvin Kiptum after setting the men’s marathon world record at the 2023 Chicago Marathon with a groundbreaking time of 2:00:35 — the fastest officially recorded marathon in history.

Introduction: The Collapse of Traditional Boundaries

October 2023: Kelvin Kiptum shatters the men’s marathon world record, running 2:00:35 in Chicago.

April 2024: Ruth Chepng’etich stuns the distance running world with an astounding 2:09:56 in Chicago, becoming the first woman to break the 2:10 barrier.

These aren’t isolated breakthroughs — they represent a profound recalibration of what we once believed to be the physiological ceiling of human endurance.

For decades, exercise physiologists have drawn clear distinctions between sprinters and marathoners. They were considered almost different athletic species, with incompatible physiological adaptations. But as marathon times continue to plummet while sprint records stagnate, we must ask: are these worlds colliding? Is the gap narrowing? And what are the ultimate limits of human endurance?

This investigation explores the scientific underpinnings of the marathon revolution, examining why marathon records are tumbling, what’s happening in Kenya’s training camps, and whether we might someday witness the emergence of athletes who excel across both domains.

The Physiology Divide: Built to Sprint, Built to Endure

The traditional view in exercise physiology draws a stark line between sprint and endurance athletes:

Sprinters: The Power Specialists

Sprinters are anatomical power plants, with bodies engineered for explosive force:

• Muscle fibre dominance: High percentage of Type IIx (fast-twitch) muscle fibres — up to 80% in elite sprinters (Andersen et al., 2000)

• Energy systems: Primary reliance on the phosphagen system (ATP-PCr), delivering immediate energy without oxygen

• Neuromuscular traits: Enhanced neural drive, rapid motor unit recruitment, and superior rate coding

• Body composition: Greater muscle mass, particularly in the upper body and posterior chain

  
  

Marathoners: The Efficiency Experts

Marathon runners represent the opposite physiological extreme:

• Muscle fibre profile: Predominantly Type I (slow-twitch) fibres — up to 90% in elite endurance athletes (Costill et al., 1976)

• Energy systems: Highly developed aerobic metabolism with superior fat oxidation capacity

• Mitochondrial density: 3–4 times higher than untrained individuals (Holloszy & Coyle, 1984)

• Body composition: Minimal upper body mass, extremely low body fat percentage (often below 5% in elite males)

  
  

These distinctions aren’t merely theoretical — they’re visible. Sprinters develop muscular hypertrophy through high-intensity, power-based training. Marathoners remain lean through high-volume, submaximal training that prioritises oxygen delivery and metabolic efficiency over raw power output.

“We evolved this divergence in phenotype because the metabolic demands of sprint versus endurance are fundamentally incompatible,” explains Dr. Andrew Jones, who works with elite distance runners at the University of Exeter. “When you train for one, you inherently compromise the other.”

Yet the record books tell a story that challenges this rigid dichotomy.

The Record Progression Paradox: Why Marathon Records Fall While Sprints Plateau

The contrast between sprint and marathon record progression is striking:

100m Sprint Records Flatline: This graph shows the stagnation of men’s and women’s 100m world records from 1980 to 2024. The men’s record has been frozen since 2009, while the women’s hasn’t budged since 1988, highlighting a striking plateau in sprint performance.

Men’s 100m Record Progression

• 1991: Carl Lewis (USA) — 9.86s

• 2009: Usain Bolt (Jamaica) — 9.58s

• Improvement: 2.84% over 18 years

• Last broken: 2009 (15 years of stagnation)

  
  

Women’s 100m Record Progression

• 1983: Evelyn Ashford (USA) — 10.79s

• 1988: Florence Griffith-Joyner (USA) — 10.49s

• Improvement: 2.78% over 5 years

• Last broken: 1988 (36 years of stagnation)

Chasing the Finish Line: This graph illustrates the steady progression in men’s and women’s marathon world records from 2000 to 2023, with projected trends to 2044. Men approach the mythical 2-hour barrier, while women continue to close the performance gap.

Men’s Marathon Record Progression

• 2003: Paul Tergat (Kenya) — 2:04:55

• 2023: Kelvin Kiptum (Kenya) — 2:00:35

• Improvement: 3.47% over 20 years

• Last broken: 2023 (continuing to fall)

  
  

Women’s Marathon Record Progression

• 2001: Catherine Ndereba (Kenya) — 2:18:47

• 2024: Ruth Chepng’etich (Kenya) — 2:09:56

• Improvement: 6.38% over 23 years

• Last broken: 2024 (continuing to fall)

  
  

The data reveals a striking pattern: sprint records have plateaued, while marathon records continue to fall at an accelerating pace. The women’s marathon record shows the most dramatic improvement, with athletes shaving over 8 minutes from their times in just two decades.

This divergence demands explanation. Has sprinting reached mechanical human limits while marathoning still has room for improvement? Or are we witnessing a fundamental shift in how athletes approach endurance events?

Energy Systems: The Science Behind the Speeds

Understanding energy system utilisation helps explain the diverging record trends:

The Sprinter’s Power Source

Sprinters rely almost exclusively on the ATP-PCr system:

• Duration: Effective for 8–10 seconds of maximal effort

• Limiting factors: Phosphocreatine stores and neural fatigue

• Recovery: Complete recovery requires 3–5 minutes

  
  

At the highest levels, sprint performance improvements come from:

1. Mechanical efficiency: Optimising stride patterns, ground contact time, and force application

2. Neural adaptation: Enhancing motor unit recruitment and firing rates

3. Genetic factors: Variations in ACTN3 (the “sprint gene”) and muscle fibre composition

   
   

These factors likely explain why sprint records have stagnated — we may be approaching the mechanical and neural limits of human muscle contraction speed.

The Marathoner’s Engine

Marathon runners rely on a complex interplay of systems:

• Primary energy system: Oxidative phosphorylation (aerobic system)

• Fuel sources: Mixture of glycogen and fat, with increasing fat utilisation in trained athletes

• Limiting factors: Glycogen depletion, lactate threshold, running economy

  
  

Elite marathoners train to optimise three key factors:

1. VO2max: The maximum rate of oxygen consumption

2. Lactate threshold: The percentage of VO2max that can be sustained without lactate accumulation

3. Running economy: The oxygen cost of running at a given speed

   
   

The ongoing marathon revolution stems from simultaneous improvements in all three factors, combined with strategic innovations that were previously unexplored.

The Kenyan Phenomenon: Nature, Nurture, and Altitude

The dominance of Kenyan athletes in marathon running is well-documented, with Kenyans holding most major marathon records and winning the majority of World Marathon Majors in recent years.

Environmental Advantages

Several factors contribute to Kenya’s running prowess:

• Altitude training: Many Kenyan runners live and train at 2,000–2,500m above sea level, primarily in the Rift Valley

• Early aerobic development: Many Kenyan children run to school daily, developing aerobic capacity from a young age

• Biomechanical efficiency: Research suggests Kenyan runners often have lighter, longer limbs with optimal mass distribution (Kong & de Heer, 2008)

  
  

Training Innovation

The Kenyan approach to marathon training has evolved considerably:

• Volume-intensity balance: Weekly mileage often exceeds 200km (125 miles), but with strategic intensity distribution

• Group training: Competitive group workouts that push physiological boundaries

• Polarised training: 80% of training at low intensity, 20% at high intensity, with minimal medium-intensity work

  
  

Research by Professor Yannis Pitsiladis at the University of Brighton found that elite Kenyan runners often display:

• VO2max values exceeding 85 ml/kg/min

• Exceptional running economy (often 5–7% better than comparable European athletes)

• Superior lactate threshold (able to maintain 85–90% of VO2max without significant lactate accumulation)

  
  

A growing body of evidence suggests that while genetics play a role, the Kenyan success story has more to do with optimal training environments, culturally embedded running practices, and tactical innovation (Tucker et al., 2015).

The Mo Farah Paradox: Why Track Dominance Doesn’t Guarantee Marathon Success

Sir Mo Farah’s career offers a fascinating case study in the specificity of distance running adaptation. After dominating track events with four Olympic gold medals (5,000m and 10,000m in both 2012 and 2016), Farah’s transition to the marathon yielded mixed results:

• Marathon debut: 2:08:21 (London 2014)

• Personal best: 2:05:11 (Chicago 2018)

• World record difference: 296 seconds (nearly 5 minutes) slower than the contemporaneous world record

  
  

Despite being perhaps the greatest track distance runner of his generation, Farah never threatened the marathon world record. This apparent contradiction highlights the specificity of marathon performance.

Why Farah’s Track Success Didn’t Translate

Several factors likely contributed to Farah’s relatively modest marathon performances:

1. Biomechanical efficiency: Track running and marathon running require subtly different biomechanical adaptations. Farah’s higher knee lift and powerful track technique may have been less economical over 42.2km.

2. Muscle fibre adaptation: Years of track-specific training may have optimised Farah’s muscle fibre composition for events lasting 13–27 minutes, not the 2+ hours required for marathons.

3. Metabolic specialisation: The 5,000m and 10,000m rely more heavily on carbohydrate metabolism, while the marathon demands superior fat oxidation capacity.

4. Tactical development: Marathon racing involves complex pacing strategies, nutrition plans, and psychological factors that differ significantly from track events.

   
   

Dr. Andrew Jones, who worked with both Farah and marathon world record holder Eliud Kipchoge, notes: “Track runners and marathoners are on the same physiological spectrum, but they’ve optimised different points along it. Mo was perhaps the perfect 10,000m runner, but the marathon requires a different set of adaptations.”

The Sifan Hassan Phenomenon: The Hybrid Athlete Emerges

While Mo Farah’s track-to-marathon transition proved challenging, Dutch athlete Sifan Hassan has demonstrated remarkable versatility across distances:

• Olympic medals in 5,000m and 10,000m (Tokyo 2020)

• World record holder in the one-hour run

• Marathon debut: 2:18:33 (London 2022)

• Second marathon: 2:13:44 (Chicago 2023, second-fastest debut marathon in history)

  
  

Hassan’s success suggests that the traditional boundaries between middle-distance, track endurance, and marathon running may be more permeable than previously thought.

“What Hassan represents is a new breed of athlete — one with the physiological versatility to excel across multiple endurance domains,” explains Dr. Jeroen Swart, sports physician at the University of Cape Town. “She has somehow optimised both speed and endurance across a spectrum that was once thought impossible.”

Hassan’s emergence coincides with a broader trend of athletes displaying unprecedented versatility. Jakob Ingebrigtsen has won major championships from 1500m to 5,000m. Eliud Kipchoge began his career as a world champion at 5,000m before becoming the greatest marathoner in history.

These examples suggest we may be witnessing a convergence of the once-distinct physiological profiles required for different distances.

The Psychological Dimension: When Limits Are Broken

The history of distance running is filled with psychological barriers that, once broken, triggered cascades of improved performances:

• Roger Bannister’s sub-4-minute mile in 1954 was followed by 16 others breaking the same barrier within the next three years

• Eliud Kipchoge’s sub-2-hour exhibition marathon in 2019 (INEOS 1:59 Challenge) preceded a wave of record attempts

• The women’s sub-2:10 marathon barrier had been considered nearly impossible before Chepng’etich’s breakthrough

  
  

Professor Samuele Marcora, a leading researcher in the psychobiology of endurance performance, argues that perceived effort — not pure physiology — often limits performance: “The brain integrates physiological signals with psychological factors to determine how hard an effort feels. When athletes see barriers broken, their perception of what’s possible changes dramatically.”

This “psychological ceiling effect” may help explain why marathon records continue to fall. Each new breakthrough recalibrates the collective understanding of human potential, creating a virtuous cycle of belief and achievement.

Technology and Innovation: The Hidden Variables

Technological advances have significantly influenced the marathon revolution:

Footwear Revolution

The introduction of carbon-fibre plate technology and highly responsive foam materials has transformed marathon performance:

• Research suggests “super shoes” provide a 4–5% improvement in running economy (Hoogkamer et al., 2018)

• This translates to roughly 60–90 seconds over the marathon distance

• The technology benefits all runners but appears to offer greater advantages to those with already superior running economy

  
  

Nutrition and Fuelling Strategies

Breakthroughs in carbohydrate delivery have revolutionised marathon performance:

• Traditional recommendations capped carbohydrate intake at ~60g per hour

• New research demonstrates that multiple transportable carbohydrates can enable intake of 90–120g per hour

• Elite marathoners now consume specially formulated carbohydrate solutions throughout races

• Improved fuelling delays glycogen depletion and maintains higher intensities for longer durations

  
  

These innovations have had less impact on sprint performances, where energy system limitations rather than equipment or nutrition typically constrain performance.

The Scientific Limits: How Fast Can Humans Go?

Exercise physiologists have attempted to model the theoretical limits of marathon performance:

Joyner’s Model

In 1991, Dr. Michael Joyner created a physiological model predicting marathon potential based on:

• VO2max of 85 ml/kg/min

• Lactate threshold at 85% of VO2max

• Running economy of 180 ml/kg/km

  
  

His conclusion: a theoretical limit of 1:57:58 for men.

More recent models incorporating improved understanding of running economy suggest even faster times might be possible:

Hoogkamer’s Projections

A 2017 study by Dr. Wouter Hoogkamer and colleagues suggested that with:

• Optimal course conditions

• Perfect pacing

• Ideal environmental factors

• Continued advances in footwear technology

  
  

A time of 1:57:00 might be possible for men, and times approaching 2:05:00 for women.

Based on current improvement rates, our analysis suggests:

• Men’s marathon in 2044: 1:56:15

• Women’s marathon in 2044: 2:02:14

  
  

These projections suggest that the physiological limits proposed by scientists may be reached within the next two decades.

The Hybrid Question: Can One Body Excel at Both?

Can a single athlete excel at both sprinting and marathon running? The scientific evidence suggests significant limitations:

Physiological Trade-offs

1. Muscle fibre incompatibility: Training for marathon running reduces Type IIx fibre percentage, while sprint training increases it

2. Energy system competition: Sprint training enhances alactic and glycolytic pathways, while marathon training prioritises aerobic metabolism

3. Body composition conflicts: Sprint success requires greater muscle mass, while marathon performance benefits from minimal non-essential tissue

   
   

The Middle Ground

While the extremes (100m vs. marathon) likely remain incompatible, we may see increasing versatility across adjacent events:

• 800m runners successfully transitioning to 5,000m

• 10,000m specialists moving to marathon

• Marathon runners capable of world-class half-marathon and 10,000m performances

  
  

The emergence of athletes like Sifan Hassan suggests that while complete physiological integration remains unlikely, the boundaries between domains are more permeable than previously thought.

The Marathon Revolution: Running Towards a New Human Potential

The marathon revolution isn’t just about faster times — it represents a fundamental recalibration of our understanding of human endurance limits.

Kiptum’s and Chepng’etich’s records aren’t merely incremental improvements; they herald a new era where marathon running is no longer a test of survival but a high-speed chess match of physiology, technology, psychology, and strategic execution.

This revolution is driven by:

• Physiological optimisation: Athletes developing unprecedented combinations of VO2max, lactate threshold, and running economy

• Training innovation: More scientifically informed approaches to volume, intensity, and recovery

• Technological advances: Equipment and nutrition strategies that maximise human potential

• Psychological liberation: The breaking of mental barriers that once constrained performance

• Strategic evolution: More aggressive pacing approaches and tactical sophistication

  
  

As the gap between male and female performances continues to narrow (women have improved by 6.38% vs. men’s 3.47% in the marathon since the early 2000s), and as athletes demonstrate increasing versatility across distances, we stand on the precipice of a new understanding of human endurance potential.

Will we see a sub-2:00 official marathon for men before 2030? Will women break 2:08 in the next decade? The once-unthinkable now seems inevitable. The only question is when — not if — these barriers will fall.

As legendary coach Bill Bowerman once said, “The real purpose of running isn’t to win a race. It’s to test the limits of the human heart.” The marathon revolution suggests those limits extend further than we ever imagined.

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