What's Limiting Your VO₂ Max? How to Train Based on Your Limiter
You know your VO₂ max number. Maybe you got it from a lab test, a fitness watch, or a gym assessment. And you've been told that higher is better.
But here's what nobody tells you: knowing your VO₂ max is almost useless if you don't know what's capping it.
The fix for a delivery problem is completely different from the fix for a utilization problem. Train the wrong one and you're wasting months of work.
VO₂ Max Is a Two-Part System
When you exercise, oxygen uptake increases linearly with intensity until you hit a ceiling. That ceiling is your VO₂ max.
But VO₂ max isn't a single bottleneck. It's the product of two distinct processes:
Delivery: How much oxygen your heart, blood vessels, and red blood cells can transport to your muscles.
Utilization: How efficiently your muscles extract and use that oxygen to produce ATP.
Most people are limited by one or the other. The training fix is completely different for each.
How to Identify Your Limitation
The 5-15 Test (Gold Standard, Needs NIRS)
The most accurate assessment uses a Near-Infrared Spectroscopy device that measures muscle oxygenation in real time:
Start at low intensity for 5 minutes. Rest 1 minute.
Increase intensity. Repeat: 5 minutes on, 1 minute rest.
Continue increasing until exhaustion.
Monitor muscle oxygenation (SmO₂) and total hemoglobin throughout.
Delivery-limited athletes see muscle oxygenation drop as intensity increases. During rest periods, blood flow spikes — the heart is trying to deliver more oxygen. But at exhaustion, the blood flow peaks stop increasing. The heart can't deliver any more, even though the muscles could still use more.
Utilization-limited athletes see muscle oxygenation stay relatively stable even at high intensities. Blood flow increases appropriately. The muscle simply doesn't deoxygenate much — it's receiving plenty of oxygen but can't extract and use it efficiently.
No NIRS Device? Use These Proxies
You can estimate your limitation without expensive equipment:
Signs you're delivery-limited:
High muscle mass, BMI above 26 (with low body fat)
Better at interval-style workouts than long grinding workouts
Threshold power below 3 watts per kg
Power/strength athlete background
Signs you're utilization-limited:
Medium muscle mass, normal BMI (20–25)
Better at long grinding workouts than interval-style workouts
Threshold power above 3 watts per kg
Endurance athlete background
Think of it this way: a muscular, powerful athlete like Brent Fikowski is likely delivery-limited. His heart can't supply enough oxygen to all that muscle mass during sustained efforts. A lean, endurance-oriented athlete like Patrick Vellner is probably utilization-limited. His delivery system is excellent, but mitochondrial respiration is the bottleneck.
Train for Your Limiter (Not Someone Else's)
If You're Delivery-Limited: Long Intervals
Goal: Improve cardiac output and oxygen delivery.
Interval length: 4–8 minutes
Rest: 2–4 minutes (2:1 work-to-rest ratio)
Intensity: Around threshold power — hard but sustainable
Frequency: 2–3 times per week
These longer intervals stress the cardiovascular system without pushing into the red zone that creates excessive recovery demands. You're training your heart to pump more blood and your body to deliver more oxygen.
If You're Utilization-Limited: Short, All-Out Intervals
Goal: Improve mitochondrial respiration and oxygen extraction.
Interval length: 20–40 seconds
Rest: 4–5 minutes (1:10 or 1:12 work-to-rest ratio)
Intensity: All-out, maximal effort
Frequency: 2–3 times per week
These short, explosive intervals push your muscles to extract and use oxygen at maximum capacity. The long rest ensures full recovery for each effort — quality over quantity.
The Power Curve Tells the Story
Your power curve — how much power you can produce at different time domains — reveals your limiter:
Delivery-limited athletes have very high sprinting power but drop off quickly as duration increases.
Utilization-limited athletes have lower peak power but maintain it much longer.
This is why different body types excel at different events. A 20-minute grinding event favors utilization-limited athletes. A 3-minute max effort favors delivery-limited athletes.
If you've ever wondered why the guy who crushes short metcons falls apart in longer ones (or vice versa), this is why.
Key Takeaways
VO₂ max is limited by either oxygen delivery (heart/blood) or oxygen utilization (muscles/mitochondria) — and the training fix is completely different for each.
Delivery-limited athletes need long intervals (4–8 min) at threshold intensity with moderate rest.
Utilization-limited athletes need short, all-out intervals (20–40 sec) with long rest (4–5 min).
Estimate your limitation using body type, threshold power, and performance profile if you don't have access to NIRS.
The 5-15 test with a NIRS device is the gold standard for identifying your limitation.
Training the wrong limitation wastes time and can lead to overtraining.
This article is based on research and insights from the WOdScience YouTube channel, featuring exercise physiology research from ETH Zurich.
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