Original episode & show notes | Raw transcript
This document synthesizes and explains the advanced concepts in exercise physiology and training methodology as presented in the podcast transcript. The discussion revolves around a specific, physiologically-driven approach to VO2 max training and offers a critical lens through which to view popular training methods and scientific studies.
The central thesis of the hosts’ VO2 max training philosophy is that the primary long-term limiter of VO2 max (maximal oxygen uptake) is stroke volume—the amount of blood the heart pumps with each beat. Therefore, the most effective training should be designed specifically to increase this capacity.
Diastole is the phase of the heartbeat when the heart muscle relaxes and the chambers fill with blood.
Diastolic filling time is the duration of this filling phase. A key goal of the prescribed training is to maximize the amount of blood that returns to and fills the heart’s ventricles before they contract.
Frank-Starling Mechanism: This physiological principle states that the more a heart ventricle is stretched by incoming blood, the more forcefully it will contract. By increasing venous return and maximizing diastolic filling, the heart walls are stretched more, leading to a stronger contraction and, over time, cardiac remodeling (a stronger, larger heart) that increases stroke volume.
The primary tool used to achieve this goal is high-cadence cycling. This is not for “neuromuscular” reasons in this context, but for its direct impact on cardiovascular dynamics.
The Muscle Pump: The large muscles of the legs act as a peripheral pump. Rhythmic, rapid contractions at high cadence squeeze the veins, actively pushing deoxygenated blood back towards the heart. This significantly enhances venous return.
Reduced Intramuscular Pressure: Compared to low-cadence, high-force pedaling, high-cadence work involves lower peak forces. This lower force reduces the pressure within the muscle, preventing the “pinching” of blood vessels and allowing for more continuous blood flow, further aiding venous return.
The Pendulum Effect: The simple kinetic energy of the legs swinging in a circular motion at high speed contributes to the cardiovascular stimulus, independent of the force being produced.
The key takeaway is that power output is secondary to the physiological stimulus. While high-cadence work may result in a slightly lower power output (e.g., 10-25 watts less) for a given effort, the hosts argue this is a worthwhile trade-off for the superior cardiac stimulus that drives long-term VO2 max improvements.
Building on the core theory, the podcast provides specific guidance on how to structure and execute these intervals.
Cadence is King: The primary focus is on maintaining a high cadence. This should be individualized, typically 10-20 RPM higher than an athlete’s naturally preferred cadence for that intensity. It should be challenging but not so high that power production falls off a cliff.
Effort Over Power: The intervals are described as “all-out” for the given duration, but not a frantic sprint from the start. The goal is to achieve the highest possible rate of oxygen consumption, which means breathing should be deep and maximal. Athletes should not be fixated on hitting a specific power target, especially if it means sacrificing cadence.
Pacing: A good effort involves a hard start to overcome inertia, followed by settling into the highest sustainable effort level. The power may naturally decline over the course of the interval, which is expected and acceptable.
Rest Intervals: Rest should be as short as possible while still allowing the athlete to feel ready for the next maximal effort. This can be progressive; as fatigue builds throughout a session, rest periods may need to be extended. This is a key metric for a coach to monitor fatigue.
Seated vs. Standing: The hosts strongly recommend avoiding standing. While standing opens the hip angle, it forces a lower cadence. This increases the force required per pedal stroke, which recruits larger, more powerful, and less aerobic motor units. These units fatigue faster and are not the primary target of this specific training adaptation.
A crucial point is that high-cadence VO2 max work is a training tool, not a racing tactic. An athlete should not try to maintain this artificially high cadence during a race or a KOM attempt. In a competitive situation, the body will naturally default to its most efficient and powerful cadence, and this is what should be used. The training adaptation (increased stroke volume) will be available regardless of the cadence used on race day.
How these intense sessions fit into a broader training plan is critical for success and avoiding burnout.
Focused Blocks: VO2 max work is best performed in a dedicated, focused training block (e.g., 2-4 weeks). This creates a significant, targeted stimulus that the body can then adapt to during a subsequent recovery and maintenance phase. Sprinkling these efforts throughout the year is seen as less effective.
Don’t Mix Stimuli: During a VO2 max block, other forms of high-intensity work, specifically FTP/Threshold intervals, should be avoided. The reasoning is twofold:
The aerobic stimulus from VO2 max work is sufficient to maintain, and sometimes even slightly improve, FTP.
Adding threshold work creates excessive fatigue, which can compromise the quality of the key VO2 max sessions and blunt the overall adaptive signal.
Preparation is Required: An athlete should not jump directly into a hard VO2 max block from an off-season or a period of low-intensity base training. A preparatory phase of training is needed to build the durability and fitness required to handle the intensity and recover from it.
Solidifying Gains: The adaptations from a VO2 max block are “realized” in the weeks and months that follow through consistent training, proper recovery, and adherence to the fundamental principles of progressive overload and rest. There is no special workout to “lock in” the gains; it is the process of recovering from the stimulus and then continuing with a well-structured plan that integrates the new, higher fitness level.
A significant portion of the podcast is dedicated to a critique of a popular study by Bent Rønnestad, which concluded that short, intermittent intervals (e.g., 30 seconds on, 15 seconds off) were superior to longer 4-5 minute intervals for improving performance. The hosts argue that methodological flaws in the study likely invalidate this conclusion.
The hosts contend that the group performing the 4x5-minute intervals was likely working at or even below their FTP, not at a true VO2 max intensity. Their evidence is based on a critical look at the study’s methods:
Unreliable FTP/Threshold Testing:
Lactate Measurement: The study used a step test with 5-minute stages. The hosts argue that 5 minutes is not long enough for blood lactate to reach a steady state. Lactate spikes at the onset of an effort and then settles. By measuring within 5 minutes, the study likely overestimated the true lactate concentration, leading to an underestimation of the power at lactate threshold (FTP).
20-Minute Power Test: The 20-minute test was performed after a lactate test and a ramp test to exhaustion. The accumulated fatigue makes it highly unlikely that the athletes could produce a true maximal 20-minute power, again leading to an underestimation of their FTP.
Ambiguous RPE Instructions: The instructions for the 4x5-minute group were based on RPE (Rate of Perceived Exertion). The hosts point out that the Borg scale is notoriously ambiguous for high-performance athletes. A rating of “hard” or “highest level you can sustain” could easily be interpreted as threshold pace rather than a truly maximal 5-minute effort, especially if the athlete’s goal is to complete all four intervals at a steady power.
The Human Element: The discrepancy between the likely maximal effort intended by the researchers and the sub-maximal effort suggested by the power and lactate data points to a potential failure in communication or athlete compliance.
Conclusion of the Critique: Because the 4x5-minute group was likely not training at a true VO2 max intensity, the study was not a valid comparison between two different types of VO2 max work. Instead, it was likely comparing a sub-threshold/threshold workout to a high-intensity intermittent workout, making the latter’s superiority unsurprising but not for the reasons claimed.