Original episode & show notes | Raw transcript
This document provides a detailed educational breakdown of the key concepts discussed in the Empirical Cycling Podcast featuring Dr. Andy Coggan. The content is structured for an educated student audience, aiming to clarify the science, history, and application of these ideas in endurance sports.
Dr. Coggan’s work is most famously associated with FTP. The podcast delves into its origin, true meaning, and common misconceptions.
The primary motivation for creating the term “Functional Threshold Power” was educational. Dr. Coggan explains that in the scientific literature, there were over 20 different definitions of “lactate threshold,” leading to immense confusion among coaches and athletes.
The Problem: An athlete might get a lab test result stating their “lactate threshold” (e.g., the first rise in lactate) is at a power output (e.g., 170 watts) far below what they know they can sustain for a long duration (e.g., 220 watts in a 40k time trial). This created a disconnect between scientific terminology and real-world experience.
The Solution: FTP was created to bypass the confusing “lactate” terminology and focus directly on performance data from a power meter. It provides a single, functional metric that corresponds to what coaches and athletes intuitively understood as the “fuzzy line” or “coach’s threshold”—the intensity above which fatigue rapidly accelerates.
Core Concept: FTP is a functional surrogate for the physiological state known as the Maximal Lactate Steady State (MLSS) or Maximal Metabolic Steady State. This is the highest intensity at which lactate production and clearance can be balanced, allowing for a prolonged, albeit difficult, effort.
A persistent misunderstanding is that FTP is defined as the highest power one can sustain for exactly 60 minutes. Dr. Coggan clarifies this is not, and has never been, the case.
The Origin: The “about an hour” or “40k time trial” guideline was the original basis for estimating FTP. This is because, for many trained cyclists, the duration of an all-out 40k TT is in the range of 40-70 minutes, which aligns with the typical time to exhaustion (TTE) at MLSS.
Physiological Variance: The actual TTE at FTP/MLSS varies significantly.
Untrained individuals might only last ~30 minutes.
Highly trained endurance athletes can often sustain it for longer, from 40 to 70 minutes.
The fitter an athlete is, the longer their TTE at threshold tends to be.
The Power-Duration Relationship: The power-duration curve is very flat in this region. The difference in average power between a 45-minute effort and a 65-minute effort is only a few percent. Therefore, using a 40k TT (regardless of its exact duration) provides a robust and practically useful estimate of the underlying physiological state (MLSS).
The podcast touches on the debate of whether CP is more “physiological” than FTP. Dr. Coggan argues this is a false distinction.
Shared Goal: Both FTP and CP are models attempting to define the same fundamental concept: the boundary between sustainable and unsustainable exercise intensities.
Methodological Differences:
FTP: A broader, more overarching concept that can be estimated through various methods (e.g., a single long effort, 95% of a 20-minute test).
CP: A parameter derived from a specific mathematical model applied to several all-out efforts of varying durations. The exact value depends on the model used and the test durations chosen.
Evolution of CP: Dr. Coggan notes that the concept of CP has evolved over time, with researchers refining it to more closely align with the very physiological state that FTP was designed to represent from the beginning (MLSS). Ultimately, he states, “CP is FTP.”
A significant portion of the conversation is dedicated to a critical analysis of the VLAmax concept. Dr. Coggan argues that its core premise is physiologically flawed.
VLAmax is marketed as the “anaerobic equivalent of VO2max”—a measure of an individual’s maximal glycolytic or lactate-producing rate. The model claims that an athlete’s FTP is determined by the balance between their VO2max (aerobic capacity) and their VLAmax (glycolytic power).
Dr. Coggan’s central critique is summarized in his proverb: lactate production is not a pressure-driven system (“blowing”), but a demand-driven one (“sucking”).
The Biochemistry of Muscle Contraction:
Demand: Muscle contraction begins with the hydrolysis of ATP. Muscle is unique in its ability to increase its demand for ATP by 100- to 1000-fold in milliseconds.
Robust Supply: To prevent ATP levels from plummeting (which would cause rigor), the muscle has robust, redundant, and rapid systems for ATP resynthesis: phosphocreatine hydrolysis, glycolysis, and aerobic metabolism.
Linkage: The rates of these supply pathways are intimately linked to and controlled by the rate of ATP demand.
Lactate as a Response, Not a Limiter: Glycolysis (and thus lactate production) accelerates in response to the need to resynthesize ATP quickly. A higher rate of ATP breakdown (i.e., higher power output) “sucks” substrates through the glycolytic pathway faster.
No “Maximal” Rate: Dr. Coggan argues that during whole-body exercise, athletes do not reach the true maximal enzymatic capacity of their glycolytic pathway. There is always a reserve. Therefore, what is being measured is a peak rate of lactate production (VLApeak) determined by ATP demand, not a maximal enzymatic limit (VLAmax).
The Practical Takeaway: If you want to know someone’s glycolytic power, measure their 15-second sprint power. Wrapping it in a pseudo-scientific concept like VLAmax, which is based on flawed assumptions, is unnecessary and misleading.
The discussion explores the fundamental reasons for fatigue and the intricate systems that govern performance.
FTP/MLSS represents the point where ATP demand can be sustainably met, primarily by aerobic pathways.
Below Threshold: ATP demand is met aerobically. Byproducts are cleared effectively.
Above Threshold: ATP demand outstrips the rate of aerobic ATP production. To make up the shortfall, there is an exponential increase in glycolysis and phosphocreatine breakdown. This leads to the accumulation of metabolites (e.g., H+, ADP, Pi) associated with fatigue and alters the cell’s energetic state, ultimately inhibiting contraction.
Dr. Coggan introduces a more recent concept in muscle physiology that adds a layer of complexity to our understanding of contraction and energy conservation.
Energy Conservation: In resting muscle, most myosin cross-bridges are in a “super-relaxed state,” lying flat against the myosin filament. This is a crucial energy-saving mechanism to prevent unnecessary ATP hydrolysis.
Mechanosensing: The muscle “turns on” in proportion to the force required. Tension on the muscle filament causes myosin heads to move away from this relaxed state, making them available to bind with actin. This process, called mechanosensing, ensures that only the necessary number of cross-bridges are activated for a given task.
Implications: This refines the classic textbook view of muscle activation. It’s not just calcium turning the switch “on”; it’s a multi-stage process involving both the thin (actin) and thick (myosin) filaments, designed for exquisite control and energy efficiency.
Fatigue is never caused by a single factor.
Peripheral Factors: Glycogen depletion (particularly in specific fiber types), accumulation of metabolic byproducts, and alterations in high-energy phosphate levels all contribute.
Central Factors (The Brain): The role of the central nervous system is critical. Fatigue occurs when the brain can no longer generate sufficient central motor drive to overcome noxious peripheral feedback signals. As Dr. Coggan puts it, on the Borg scale, “fatigue is when your perceived exertion hits 18.” It’s not necessarily that central drive decreases, but that it fails to increase enough to maintain the required output. The title of a key paper sums it up: “Exercise Begins and Ends in the Brain.”
The podcast highlights the gap between pure science and practical coaching, emphasizing the importance of context and interpretation.
Dr. Coggan intentionally called his power-based training guides “levels,” not “zones,” for a specific reason.
“Zones” imply prescription: The term “zone” encourages rigid thinking, where an athlete feels they must stay within a narrow power range (e.g., “I can’t go out of Zone 2 on this hill”). This leads to training that is less specific to the demands of racing.
“Levels” imply description: The term “level” is meant to describe the intensity and physiological strain of an effort. It provides a common language to understand training without being overly restrictive.
Dr. Coggan is clear that he is an exercise physiologist, not a coach. His goal has been to develop tools and concepts to help coaches and athletes, but his professional focus has been on fundamental research, often funded by the NIH and conducted in medical schools. This perspective, free from the demands of coaching, may have helped in the development of objective, physiology-based tools.
While power data is objective, subjective feedback remains invaluable. Session RPE (rating a workout on a 1-10 scale about 30 minutes after completion) is a powerful tool. When RPE is abnormally high for a given power output, or power is low for a given RPE, it’s a red flag for a coach, indicating potential issues like poor sleep, stress, or impending illness.