I came across a conversation recently comparing VO₂max testing to power data from TrainingPeaks. It’s a familiar debate and one I’ve spent a lot of time thinking about. After running hundreds of VO₂max tests myself and coaching athletes across a range of abilities, I thought I’d share my perspective.

In short: TrainingPeaks peak power charts are more useful for most athletes than direct physiological testing. Five-minute power in particular is a surprisingly reliable proxy for VO₂max in well-trained individuals. But beyond that, power data tells you what matters most, what an athlete can actually do out in the real world.

VO₂max has its place, of course. But it’s not the be-all and end-all. Metabolic testing equipment is notoriously sensitive, and the accuracy of the results can vary far more than manufacturers claim. Unless you’re working with a skilled practitioner in a tightly controlled environment, you risk drawing conclusions from noisy or misleading data.

By contrast, peak power charts are brutally honest. They’re built from real efforts, in real conditions, with meaningful context: was it during a race? Were they fatigued? Was it off the back of a big week? That kind of data is gold for coaches and it’s already in front of us if we know how to use it.

What’s more, this data evolves. It grows with the athlete. It reflects adaptation, plateaus, breakthroughs. It shows you the energy systems that need work and the durations where confidence is building. You simply can’t get that from a single lab test.

That’s not to say physiology isn’t important, it is. But its real power comes in solving specific questions or refining things at the sharp end. For the day-to-day of coaching and training, performance-based metrics like peak power give us more clarity, more consistency, and more direction.

So while VO₂max still gets all the attention, I’d argue the humble 5-minute power line on a TrainingPeaks chart is often doing the heavier lifting.