🎙️ Episode 20:  How Fast Can You Run a Marathon?

 

Making Sense of Marathon Predictions

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Your watch predicts one time. A race calculator gives you another. Your training suggests something different again. How do you decide what pace to start at?

 

In this solo episode of The Rehab Runway, Luke Nelson explores the evidence behind marathon prediction and how to turn an estimate into a realistic race plan.

 

We look at what your recent 5 km, 10 km or half marathon can tell you, how commonly used calculators perform against actual marathon results, and why the training behind a prediction matters. We also explore physiological testing, durability, smartwatch estimates and the influence of race-day conditions.

 

Whether you’re preparing for Melbourne Marathon or planning your next marathon elsewhere, this episode will help you assess your target with more confidence.

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🏃 In this episode we cover:

⏱️ What can a shorter race tell us?

How to interpret recent race results, why the circumstances matter, and what to investigate when your 5 km and half-marathon performances suggest different marathon targets.

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🧮 Riegel and Jack Daniels’ VDOT

How these two approaches estimate equivalent performances, where they differ, and why you should consider a calculated marathon time alongside your preparation.

 

📊 The 2026 Valencia prediction model

What Oficial-Casado and colleagues found when comparing their model with VDOT, why accuracy varied by finishing-time group, and why an average error isn’t an individual prediction range.

 

🫁 VO₂max, lactate threshold and running economy

How these physiological characteristics contribute to performance, what laboratory testing can add, and why one impressive number doesn’t tell the whole story.

 

🔋 Durability: what changes as the run continues?

Why fresh fitness may not reflect what you can sustain late in a marathon. We discuss research on physiological changes after prolonged running and how to interpret patterns from your long runs.

 

📅 What training supports your target?

Consistency, training volume, long runs, tempo work and practised fuelling. We examine research on the training patterns associated with faster marathons, including the limitations of observational data and estimated intensity zones.

 

⌚ How much should you trust your watch?

What device-specific validation studies can tell us, what remains uncertain, and how to weigh a watch prediction against races and training.

 

🌡️ Heat, hills and the race plan

Why the course and conditions belong in the prediction, and how to bring the available information together when choosing an opening pace.

 

🧠 Key takeaways

• A recent race is a useful starting point, but its timing, effort and conditions matter.

• Different calculators can produce different targets from the same performance.

• Average prediction errors don’t tell you exactly how far off your own result might be.

• Training history and durability help assess whether your fitness can translate to the marathon.

• Fuelling, pacing and race conditions affect what you can deliver on the day.

 

🎧 Listen to the episode

👉 Spotify

👉 Apple Podcast

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If you found this episode useful, share it with a runner choosing their marathon target or a coach helping them prepare.

 

📖 Read more

How Accurate Is Your Marathon Prediction?

The accompanying blog explores the research, compares prediction methods and includes the Valencia formula so you can try the calculation yourself.

👉 Read here

 

🎙️ Related episode

Episode 13: Running Durability Explained with Michele Zanini

For a closer look at durability, listen to my conversation with Michele about how prolonged running changes physiology, how durability is measured and what it means for endurance performance.

 

👋 About the host

Luke Nelson is a Sports & Exercise Chiropractor, running coach and strength coach at Health & High Performance in Melbourne. He works with runners to manage injuries, build capacity and prepare for the demands of training and racing.

 

📱 Follow Luke on Instagram: @sportschiroluke

🌐 Explore the clinic, coaching and resources: Health & High Performance

 

📚 Research discussed

• Vickers & Vertosick (2016): Race-time prediction in recreational endurance runners

• Oficial-Casado et al. (2026): Predicting Valencia Marathon performance from half-marathon results

• Joyner (1991): Modelling optimal marathon performance

• Hunter & Muniz-Pumares (2025): Physiological durability and marathon performance

• Muniz-Pumares et al. (online 2024): Training characteristics across marathon performance levels

• Dai et al. (2025): Huawei Watch GT Runner race-prediction validation

• El Helou et al. (2012): Environmental conditions and marathon performance

• Minetti et al. (2002): The energy cost of uphill and downhill running

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🧠 Upcoming Courses​

• Physio Running Camp Kenya 2027

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