Original episode & show notes | Raw transcript
The podcast you provided delves into the complex and often misunderstood world of VO2 max, a cornerstone metric in endurance sports. While many athletes are familiar with the term, the hosts of the Empirical Cycling Podcast argue that common conceptions and applications of VO2 max, particularly the idea of a fixed “power at VO2 max,” are fraught with inaccuracies. This document will unpack the key concepts from the podcast, providing a detailed, science-based explanation of VO2 max, ramp tests, and the intricate relationship between them.
At its core, VO2 max represents the maximum volume (V) of oxygen (O2) that your body can uptake and utilize during intense exercise. The “dot” often seen above the V in scientific literature signifies a flux, or a rate of flow, highlighting that VO2 max is a dynamic measurement.
The gold standard for determining a true VO2 max, as established by A.V. Hill and Lupton in 1923, is the observation of a plateau in oxygen consumption despite an increase in workload. This plateau is critical because it indicates that the athlete has reached their physiological limit for oxygen utilization.
A crucial distinction made in the podcast is between VO2 max and VO2 peak.
VO2 Max: Confirmed by a plateau in oxygen uptake. This is the “true” maximal value.
VO2 Peak: The highest oxygen uptake measured during a test without a confirmed plateau.
Many studies, especially with untrained individuals, may report a VO2 peak as a VO2 max. This is a significant point of contention, as an athlete might not have reached their true physiological limit due to factors like muscular fatigue or lack of motivation.
The ramp test is a common protocol used to estimate VO2 max and determine a value often referred to as Maximal Aerobic Power (MAP), Peak Power Output (PPO), or Wmax. In a typical ramp test, the resistance is increased at regular intervals until the athlete reaches exhaustion.
The podcast highlights a critical flaw in relying solely on the power output from a ramp test: the final power value is highly dependent on the test protocol. A study cited in the podcast demonstrated that by simply changing the duration of the stages in a step test (from 30 seconds to 120 seconds), the resulting “power at VO2 max” varied by over 80 watts, even though the measured VO2 max remained the same.
The central argument of the podcast is that the concept of a single, definitive “power at VO2 max” is a fallacy. This is due to several key factors:
Anaerobic Contribution: The original assumption behind ramp tests was that the work performed was purely aerobic. However, we now know that above FTP (Functional Threshold Power), there is a significant contribution from anaerobic energy systems. This means that an athlete’s anaerobic capacity can significantly influence their final power output in a ramp test, without necessarily reflecting a higher VO2 max.
The VO2 Max Slow Component: When exercising above FTP, there is a phenomenon known as the VO2 max slow component. This means that your oxygen uptake will gradually drift upwards over time, even at a constant power output. Consequently, you can reach your VO2 max at a variety of different power outputs, depending on the duration of the effort. A three-minute all-out effort, for example, might elicit VO2 max at a much lower power output in its final minute than the peak power achieved in a ramp test.
Exercise Modality: VO2 max is exercise-specific. A triathlete will typically have a higher VO2 max when running than when cycling or swimming, due to the greater muscle mass involved. This further complicates the idea of a single, universal VO2 max value.
The podcast critiques the common practice of prescribing training zones based on a percentage of a ramp test result or a generic “VO2 max power.” The hosts argue that such approaches are often ineffective because they fail to account for the factors mentioned above.
For example, an athlete with a high anaerobic capacity might be prescribed a “VO2 max interval” at a power output that they can sustain with relative ease, without ever reaching their true VO2 max. Conversely, an athlete with a lower anaerobic capacity might find the same relative intensity to be unsustainable.
So, if “power at VO2 max” is a flawed metric, how can athletes and coaches effectively track improvements in aerobic fitness? The podcast suggests a more pragmatic approach:
Controlled Five-Minute Power Tests: Instead of relying on a single ramp test, the hosts recommend using repeated five-minute maximal effort tests. By keeping the testing conditions (freshness, nutrition, etc.) as consistent as possible and controlling for anaerobic training between tests, you can get a more reliable indication of improvements in your aerobic system.
Focus on Breathing: A simple, yet effective, subjective measure of being at or near your VO2 max is labored breathing. If you’re not breathing hard, you’re likely not working at your true VO2 max.
The podcast’s deep dive into VO2 max reveals that while it is a fundamentally important physiological marker, its practical application is far more nuanced than many believe. The idea of a single “power at VO2 max” is an oversimplification that can lead to ineffective training. By understanding the limitations of ramp tests and the complex interplay of aerobic and anaerobic energy systems, athletes and coaches can adopt more effective strategies for training and tracking progress. The key takeaway is to move beyond a single number and embrace a more holistic and individualized approach to endurance training.