The cycling and triathlon training field has changed drastically in the last few years, especially in terms of the data we can collect with tools like HR/HRV monitors and power meters. With the increased accuracy and amount of data we collect from each athlete (and increasingly powerful tools to interpret that data), we may actually be able to do away with some older means of data collection.


VO2 and blood lactate data, in particular, once required booking time at a university laboratory to gather. Now, we can instead interpret your power meter data over time to cover almost all necessary physiological data—and save you lots of time and money in the process. 


The Key Metrics and Shortcomings of a Traditional VO2 Test


By measuring the gas inhaled and exhaled, a traditional VO2 test can tell you the power or heart rate ranges where you’re aerobic or anaerobic, as well as the maximum volume of oxygen you can move through your body. If you have a higher VO2 max, you can move more oxygen, and in theory, you’ll have more power. In the past, we’d get a VO2 baseline, train an athlete, and repeat the test to see if their VO2 rose; if expired gasses showed higher oxygenation or increased efficiency, we could see if the training was working.

The stats from the VO2 test overall (including expired CO2 and Respiratory Exchange Ratio) can give you some good data, if you know how to interpret it—but the single VO2 max test value doesn’t really help us much, as it’s just a single snapshot from a single day. With ongoing power meter data recorded over time, we can get more actionable data and even get the same VO2 numbers without the lab.


How to Use WKO to Replicate VO2 Test Results


As an alternative, you can use the SRM X Power Duration model, or your max powers plotted in a curve for each time stamp from one-second max power to the max power of your longest ride. If you compare your PD curve from one 90-day training period to the next, and the second period shows higher power in your curve, then you’re watching your training work! You don’t need a lab test to confirm that you’re putting more power to the pedals and increasing speed. 


Do You Need a VO2 Test?

If we know your size and given cycling efficiency, we can also estimate your VO2 without the test—here’s a graph of modeled VO2 max based on your Power duration curve from WKO: 


Remember, this data is great, but it’s also important to remember that VO2 isn’t the whole picture of you as an athlete. The goal in training cyclists is to create more power, higher times to exhaustion and be specifically fast for the event we’re training for.