What actually determines your running performance
VO₂max, threshold and running economy: the three engines of distance running, what training improves each, and why the most trainable one is not the most measured.
Your 10K time does not depend on one number but on three, and on how they combine. Classic endurance physiology sums it up like this: how much aerobic energy you can produce at maximum, what percentage of that capacity you can hold without accumulating fatigue, and how much energy each kilometre costs you at a given pace.
Three variables explain most endurance performance
The landmark review on the physiology of champions places VO₂max, lactate threshold and efficiency (economy) as the main determinants of distance performance. Two runners with the same VO₂max can be minutes apart over 10K if they differ in threshold or economy.
VO₂max: the size of the engine
This is the maximum amount of oxygen your body can use per minute. It rises quickly in the first months of training and then plateaus: it is the variable with the most genetic ceiling and the one most overrated. It is trained mainly with long intervals at high intensity.
Long intervals improve VO₂max the most
A meta-analysis of controlled trials found larger effects on VO₂max with intervals of 2 minutes or more, at least 15 accumulated minutes of hard work per session, and programs of 4 to 12 weeks. It is the basis of the classic 4×4 minutes, or 1,000 m repeats.
Threshold: how much engine you can use without cooking it
Threshold (call it lactate threshold, anaerobic threshold or critical speed depending on the model) is the highest pace you can hold in a steady state, roughly 30–60 minutes of maximal effort. It is the variable that moves most with training in already-developed runners, and the one that best predicts half-marathon and marathon performance.
- How it feels
- Comfortably hard
- How to train it
- Tempos and long intervals
- How to estimate it
- A 30-minute test
3–4 words at a time before you have to breathe.
20–40 min at threshold pace, continuous or in blocks.
Average pace of the last 20 min of a 30-minute maximal effort.
Economy: what each kilometre costs you
Running economy separates runners with the same VO₂max
The landmark review on running economy concludes it is as strong a predictor of performance as VO₂max within homogeneous groups, and that it is modified by trainable factors: strength, tendon stiffness, technique, cadence and footwear. The methodological caveat is also there: values are not comparable between laboratories or protocols.
It is the highest-return avenue for the amateur runner with years of mileage behind them, because it does not depend on raising VO₂max: improving economy by 3% effectively lowers the cost of every one of your paces (strength for runners, technique and cadence).
Durability: the fourth factor
In long races there is a fourth variable: how much the other three degrade over the kilometres. A marathoner is not running with their first-hour economy at kilometre 35. That resistance to degradation is trained with long runs, with quality work inside the long run, and by practising eating and drinking on the move (eating and drinking on the run).
| Variable | What improves it | How much room you have |
|---|---|---|
| VO₂max | Long intervals at 90–95% of max HR | A lot in year one, little afterwards |
| Threshold | Tempos, long intervals, sustained volume | High for years |
| Economy | Heavy strength, plyometrics, technique, footwear | High and cheap for amateurs |
| Durability | Long runs, in-race nutrition | Decisive from the half marathon upwards |
Takeaways
- VO₂max: the engine. Threshold: how much of it you use. Economy: how much you spend.
- VO₂max plateaus early; threshold and economy keep improving for years.
- Long intervals (≥2 min) are the tool for VO₂max.
- Strength and technique act on economy, not on VO₂max.
- In long races, durability outranks laboratory numbers.
Sources for this chapter
- [1]Joyner MJ, Coyle EF (2008). Endurance exercise performance: the physiology of champions. The Journal of Physiology. review
- [2]Wen D, Utesch T, Wu J, et al. (2019). Effects of different protocols of high intensity interval training for VO2max improvements in adults: A meta-analysis of randomised controlled trials. Journal of Science and Medicine in Sport. meta-analysis
- [3]Barnes KR, Kilding AE (2015). Running economy: measurement, norms, and determining factors. Sports Medicine - Open. review