Running Economy Explained: Why Two Runners With the Same VO₂max Can Perform Differently

Quick answer: Running economy is how much oxygen and energy your body needs to hold a given pace. It's shaped by biomechanics as much as fitness, which is why two runners with an identical VO₂max can post very different race results. VO₂max sets your aerobic ceiling; running economy determines how much of that ceiling you can actually use.

Two runners walk into a lab. Both post a VO₂max of 58 ml/kg/min on the treadmill test, an aerobic ceiling most weekend runners would be thrilled with. Yet on race day, one of them finishes a 10K several minutes ahead of the other. Same engine size, very different results.

This isn't a fluke, and it isn't really about fitness in the way most runners think about it. It comes down to a concept that rarely gets the attention VO₂max does: running economy.

What Is Running Economy? Physiology or Biomechanics?

Running economy is the amount of oxygen (and therefore energy) your body needs to maintain a given pace. Run economically, and a 5:00/km pace might feel comfortable. Run inefficiently, and that same pace could feel like a genuine effort, even with an identical aerobic ceiling.

The honest answer to "is it physiology or biomechanics" is: both, but biomechanics usually explains the gap between two similarly fit runners.

Running economy is shaped by two sources that work together.

• Physiological factors: muscle fibre type, mitochondrial density and how efficiently your body turns fuel into movement. These are shaped by years of training and are slow to change.
• Biomechanical factors: how efficiently your body converts muscular effort into forward motion. This covers how much mechanical work each stride demands and how much energy you get back from elastic return in your tendons (your springs). These respond faster to strength work, drills and technique changes.

Systems like the MotionMetrix G2 used at FORGED by ReFormd quantify exactly this: turning your biomechanical factors into an overall running economy score, so you can see how your stride compares rather than guess.

The Engine Analogy

If VO₂max is the size of your engine (the most oxygen your body can take in and use), running economy is your fuel efficiency: how far that oxygen gets you at a given pace.

An engine size alone doesn't tell you how far a car will get on a tank of fuel. A runner with a huge aerobic engine but poor running economy is like a powerful car that guzzles fuel. Flip it around, and a runner with a smaller engine but excellent economy can keep pace with, or even beat, a runner with a bigger one.

This is precisely why VO₂max alone is a weak predictor of race performance among runners of similar training status.

VO₂max tells you the size of the engine. Running economy tells you how far you get on a tank.

Why a Bigger Engine Doesn't Always Win the Race

Endurance performance is often described as resting on three legs: your aerobic ceiling (VO₂max), the percentage of that ceiling you can sustain for a given duration (closely tied to your lactate threshold), and how efficiently you convert that effort into speed (running economy). A weakness in any one of the three limits what the other two can deliver.

Two runners with the same VO₂max but different lactate thresholds, or different running economies, will produce different race times, because performance is a product of all three, not any single number in isolation.

Mini Case Study: Same VO₂max, Two Very Different Runners

To make this concrete, consider two hypothetical runners, both testing at a VO₂max of 58 ml/kg/min.

Runner A comes from a structured distance-running background. Their running economy rating comes back in the "A++" range: efficient, low-cost movement at every pace tested.

Runner B comes from a strength and power sports background and is newer to sustained distance running. Their running economy rating lands in the "C" range: more oxygen and more energy are needed to hold the exact same pace.

Same aerobic ceiling. Same lungs and heart, essentially. But Runner A can sustain a faster pace at the same percentage of their VO₂max, because less of their oxygen supply is being "wasted" on inefficient mechanics. Over a 10K or half marathon, that gap compounds into minutes, not seconds.

This is also why background matters so much in these comparisons. Runner B may well have superior raw power and top-end speed. But distance running rewards efficiency over raw output, and that efficiency is trainable, measurable, and, importantly, visible on a gait report long before it shows up in a race result.

How Should You Actually Train to Improve Running Economy?

Here's the part that surprises a lot of runners: hammering VO₂max intervals isn't the primary way to fix running economy.

VO₂max intervals are excellent for raising your aerobic ceiling itself. But running economy responds far more to a different set of training inputs:

• Strength training and plyometrics: improves tendon stiffness and elastic energy return, so more of the energy in each stride gets recycled instead of lost
• Running-specific drills: targets cadence, vertical oscillation, and ground contact time, the exact parameters a 3D gait analysis flags
• Footwear matched to your mechanics: the right shoe can meaningfully lift energy return for your specific stride pattern
• Fatigue-resistant conditioning: running economy tends to deteriorate late in races as form breaks down, so training at race-specific durations helps you hold efficient mechanics under fatigue
• Consistent easy-pace mileage: grooves efficient movement patterns through repetition, not intensity

Not sure what your easy pace is? A Lactate Threshold Test gives you accurate training zones to build that mileage on.

VO₂max intervals train the size of your engine. Strength work, drills, mileage, and mechanical fixes train how efficiently that engine is used.

Most runners chasing performance gains would benefit more from the second category than another punishing VO₂max session.

Putting It Together: What FORGED by ReFormd's Testing Reveals

Of course, knowing that running economy matters doesn't tell you which category you actually fall into: Runner A or Runner B. That's what testing is for.

Lactate Threshold and VO₂max Tests tell you the size of your aerobic ceiling and how much of it you can sustain. A 3D Running Gait Analysis using MotionMetrix G2 tells you why your running economy is what it is: your mechanical work, your elastic energy return, your cadence, your joint loading, and where the inefficiencies are hiding.

Together, they answer the question a VO₂max number alone never can: not just how big is your engine, but how well are you actually using it.

If you're training for a specific race, pairing gait analysis with strength and power profiling through the FORM | Runner's Mechanical Bundle is a practical next step, with clear recommendations you can take into your training.

Frequently Asked Questions

Is running economy trainable? Yes. Unlike VO₂max, which has a genetic ceiling, running economy responds well to strength training, drills, and consistent mileage, and can keep improving well into a runner's career.

Does running economy matter more than VO₂max? Neither matters more on its own. They work together. A high VO₂max with poor economy, or excellent economy paired with a low aerobic ceiling, both cap performance in different ways.

How is running economy measured? It's typically measured as the oxygen or energy cost of running at a fixed pace, alongside the underlying gait mechanics, like vertical displacement, ground contact time, and elastic energy return, that explain why that cost is high or low.

Can two runners with the same VO₂max have very different race times? Yes, this is common, and running economy is usually the biggest reason why.

The Bottom Line

A high VO₂max is a real advantage, but it's only half the story. Running economy, largely a product of your biomechanics, determines how much of that aerobic ceiling you can actually translate into pace. Two runners with identical engines can have very different race outcomes, and the difference is measurable, trainable, and rarely fixed by simply running harder.

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