Original episode & show notes | Raw transcript
In the lexicon of endurance sports, few terms are as pervasive yet as poorly defined as “junk miles.” It’s a label often applied with certainty but understood with confusion. The Empirical Cycling podcast transcript reveals that this ambiguity exists for a reason: the value of any training mile is not inherent to its intensity but is dictated by a complex interplay of context, purpose, fatigue, and adaptation.
This document will deconstruct the concept of “junk miles” as discussed in the podcast, exploring the various definitions, the critical role of training volume, the limitations of rigid intensity zones, and the often-overlooked psychological benefits of “unstructured” riding.
The podcast opens by highlighting the lack of a consensus definition. This is the foundational problem. Three distinct interpretations emerge:
Definition 1: Riding Too Easy. This is the classic “noodling” or “Zone 1” ride. The argument is that the intensity is too low to stimulate meaningful physiological adaptation. As one of the coaches, GC, notes, this is a common perception he encounters.
Definition 2: Riding in the “Gray Zone”. This refers to rides that are “hard, but not too hard,” typically falling into Zone 3 or “tempo” intensity. The critique here is that these rides generate significant fatigue without providing the potent stimulus of higher-intensity intervals or the low-stress, sustainable benefits of easy, high-volume riding.
The Unified Definition: Fatigue Without Benefit. Host Kolie Moore proposes a more encompassing and functional definition: Junk miles are any miles that add fatigue without providing a commensurate benefit. This definition is powerful because it shifts the focus from a specific power zone to the outcome of the ride in the context of an athlete’s overall training plan and well-being. This will serve as our guiding principle.
A central thesis of the podcast is that total training volume is a primary driver of endurance adaptation, particularly for developing fatigue resistance (often called durability). The intensity at which this volume is accumulated is often less important than the total time spent riding.
This is illustrated by two key examples:
The Commuter Effect: Athletes who stopped commuting during the pandemic or upon retirement often experienced a noticeable drop in fitness, even though their commutes were low-intensity. This demonstrates that these seemingly “junk” miles were providing a valuable adaptive signal.
The High-Volume Camp: An athlete undertaking a 25-hour training week for the first time will gain immense benefit, even if the rides are paced at a very low intensity. The key is sustainability. Riding those hours too hard creates overwhelming fatigue that requires a long recovery, negating the gains. Riding them at a sustainable, “easy” pace allows for rapid recovery and a noticeable boost in aerobic feeling and performance.
The podcast introduces the concept of the “fatigue security blanket.” This describes a state where athletes feel productively tired from consistently riding their “easy” days too hard (e.g., at the upper end of Zone 2, around 70-75% of FTP).
The Problem: While this increases training load, the fatigue accumulates insidiously over weeks and months. Athletes mistake this chronic fatigue for progress.
The Symptoms: The tone of workout comments shifts from positive and optimistic (“I could have done more”) to negative and survival-focused (“Glad I survived that”). The athlete is trapped by a sunk-cost fallacy, believing more rest would erase all their “hard-earned” fitness.
The Takeaway: As GC illustrates with his anecdote, a 6-hour ride at 150 watts is a far superior endurance ride to a failed attempt at a 5-hour ride at 200 watts. The longer ride, even at a lower intensity, provides a greater stimulus for volume-related adaptations with less systemic fatigue.
The podcast argues against a dogmatic adherence to training zones, which were originally intended to be descriptive, not prescriptive.
Adaptations are a Spectrum, Not a Switch: There is no magic physiological switch that flips at 65% of FTP. The body’s response to training is a continuum.
Equivalency of Adaptation: For many foundational aerobic adaptations, different training intensities can lead to similar outcomes. The discussion mentions that tempo, sweet spot, and FTP intervals can all stimulate the PGC-1α signaling pathway, a master regulator of mitochondrial biogenesis (the creation of new mitochondria, which are the powerhouses of our cells). While the specific motor unit recruitment and fatigue profiles differ, the underlying aerobic-building signal can be remarkably similar.
The Goal is the Goal: The purpose of a workout is not to achieve a specific zone distribution. The purpose is to achieve a physiological goal (e.g., improve lactate clearance, increase VO2max, extend time to exhaustion). The zones are simply a tool to help guide the effort. A group ride that results in 30 minutes of “Zone 5” time on a power file does not equate to a structured VO2max workout if the efforts were too short or inconsistent to truly stress the oxygen transport system.
Whether a ride is “junk” depends entirely on its purpose within the training ecosystem.
Group Rides: A group ride can be the definition of junk miles if an athlete sits in the draft for hours doing minimal work. However, it can also be an indispensable training tool for:
Pack Skills: Learning to handle a bike in close quarters.
Race Simulation: Replicating the unpredictable surges and high power-out-of-corner accelerations that are impossible to simulate in structured training.
“Poor Man’s Motor-Pacing”: Using the draft of the group to perform intervals at speeds and cadences that would be unsustainable alone.
Mental Health and Fun: A ride that seems to have no physiological purpose can be the most important workout of the week if it serves to reduce stress, prevent burnout, and reconnect an athlete with their love for the sport. This is a tangible, crucial benefit.
The podcast introduces the idea of “periodizing fun.” Just as you periodize training stress, you should periodize enjoyment.
The example of the client swapping a stressful VO2max block for fun off-road laps illustrates this perfectly. He returned to structured training more motivated and receptive to hard work.
Given the above, true “junk miles” are rare and are defined by their negative impact on the training process. The podcast provides three clear examples:
Adding Unsustainable Stress: The client who commuted at 280 watts twice a day. This added massive fatigue with no room for recovery, making any additional structured training impossible and ultimately leading to total burnout. The fatigue far outweighed any benefit.
Derailing the Plan: The unplanned, hard group ride or race done on a recovery day or just before a key event. This introduces a massive dose of fatigue at a time when recovery is the primary goal, compromising future performance.
Blind Compliance Leading to Burnout: The athlete who executes a training plan with 100% compliance, ignoring life stress, waning motivation, and mounting fatigue. Early in the season, the miles are beneficial. Late in the season, those same workouts become “junk” because the athlete is too physically and mentally cooked to adapt positively to them. The ride becomes a frustrating obligation rather than a productive stimulus.
Ultimately, the term “junk miles” is a misnomer. It is more useful to ask: “What is the purpose of this ride, and what is its cost?” A ride has a purpose if it is building volume sustainably, targeting a specific physiological system, developing technical skills, or providing necessary mental rejuvenation. Its cost is the fatigue it generates. A ride only becomes “junk” when the cost dramatically exceeds the purpose.