“The more interesting question is whether we’ve been optimizing the amount of training athletes complete rather than the physiological condition in which they undertake their most important training”
Are We Building Fitness Too Early?
Why the best preparation for peak performance may not be more aerobic training, but arriving at the right moment with enough fitness—and the capacity to absorb what comes next.
For decades, endurance athletes have been taught a relatively straightforward model of training.
Build the aerobic base. Accumulate volume. Develop threshold. Introduce higher-intensity work. Sharpen for competition.
The progression makes intuitive sense.
A larger aerobic foundation should support more demanding training. More demanding training should produce greater fitness. And that fitness, when combined with an appropriate taper, should translate into peak performance.
But after years of training, racing, monitoring power, measuring lactate, and experimenting with different approaches, I’ve increasingly questioned an assumption embedded within this model.
Does continually developing aerobic fitness before introducing harder training actually produce a higher peak? Or can it leave an experienced athlete carrying fatigue that ultimately limits the quality and effectiveness of the work that matters most?
I’m not questioning the value of aerobic conditioning.
I’m questioning whether we have confused maximizing aerobic development with maximizing readiness for future adaptation.
Those are not necessarily the same thing.
And for experienced endurance athletes, particularly masters competitors, the distinction may be fundamental.
The traditional model: Building the engine before using it
Alan Couzens has written extensively about long-term endurance development and the sequencing of physiological adaptations.
His approach reflects a familiar progression.
General preparation emphasizes aerobic development, including cardiac adaptations, mitochondrial density, capillarization, fat oxidation, and improving efficiency.
Subsequent phases introduce increasingly specific training demands.
Depending on the athlete and event, these may progress through muscular endurance, threshold development, VO₂max training, and race-specific preparation.
Couzens’ published seasonal framework explicitly distinguishes general preparation from multiple forms of specific preparation. Importantly, he also emphasizes that the progression should be tailored to the athlete rather than applied identically to everyone.
The underlying philosophy is compelling.
Develop the physiological machinery first, then progressively demand more from it.
I don’t fundamentally disagree.
But I wonder whether we need to distinguish between an athlete who is still developing that machinery and one who has spent 15 or 20 years building it.
Consider two cyclists.
The first has been training consistently for three years. Their aerobic system is still developing rapidly. Their ability to tolerate sustained workloads is improving, and they have considerable room for adaptation through additional endurance volume.
The second has accumulated thousands of training hours over many years. They have demonstrated high VO₂max, substantial sustained power, and the ability to perform late in long, demanding races.
Should both athletes approach November through February with the same objective?
Should they both attempt to maximize aerobic development before introducing more demanding training?
Or should the experienced athlete be more concerned with preserving existing adaptations while reducing the accumulated physiological cost of training?
At some point, the objective may need to shift from building the engine to preserving the conditions that allow us to improve it.
That doesn’t invalidate Couzens’ model. It asks whether the relative importance—and duration—of its developmental phases should change as an athlete becomes increasingly trained.
Mark Allen, Phil Maffetone, and the forgotten purpose of easy training
One of the most interesting historical examples comes from six-time Ironman world champion Mark Allen and his work with Dr. Phil Maffetone.
Allen famously moved away from consistently demanding training toward a much more controlled aerobic approach.
Maffetone prescribed training using an individualized heart-rate ceiling, commonly associated with his 180 Formula.
For extended periods, Allen performed the overwhelming majority of his training aerobically, at intensities substantially below those he had previously considered productive.
Initially, he had to slow down dramatically.
Over time, however, his pace at the same controlled heart rate improved.
Eventually, higher-intensity training was introduced to develop race-specific performance.
The results became part of endurance-training history.
Allen’s subsequent success helped demonstrate that constant high-intensity training wasn’t necessary to achieve exceptional endurance performance.
But there’s a detail in the philosophy that interests me more than the heart-rate prescription.
The aerobic phase wasn’t simply about accumulating more work. It was also about controlling the physiological cost of training.
In a retrospective interview about Maffetone’s influence, Allen emphasized that successful training depended on the athlete’s ability to absorb the workload and balance training with other sources of stress.
That point deserves more attention.
We often discuss Maffetone’s approach as if its defining feature were a particular heart rate.
But what if one of its greatest benefits was that it prevented athletes from continually accumulating the kind of fatigue that compromised their response to harder training?
The distinction matters.
A lower heart rate doesn’t necessarily guarantee recovery.
An athlete can accumulate substantial fatigue through very large volumes of easy training.
Likewise, aerobic adaptations do not occur exclusively at one carefully prescribed heart rate.
Maffetone’s formula is a practical heuristic, not a direct measurement of an individual’s ventilatory or lactate thresholds.
Nevertheless, the broader principle is valuable.
Training should develop fitness without unnecessarily compromising the athlete’s capacity to recover.
And perhaps that principle deserves to become the central objective of the preparatory period.
Not simply to ride slowly.
Not necessarily to ride more.
But to develop or maintain sufficient conditioning while preserving the ability to absorb the more demanding training that follows.
What if we have misunderstood the value of Zone 2?
Zone 2 has become one of the most discussed concepts in endurance training.
It is frequently presented as the foundation of mitochondrial development, metabolic efficiency, fat oxidation, and long-term aerobic improvement.
There is substantial physiological justification for low-intensity endurance training.
Repeated muscular contractions, sustained energy demand, and the associated cellular signaling contribute to important aerobic adaptations.
But the conversation has become increasingly focused on the intensity itself.
Athletes debate whether 190 W is better than 170 W.
Whether they should ride closer to LT1.
Whether their heart rate is too low.
Whether they need three hours or five hours to obtain the optimal stimulus.
And in doing so, I wonder if we’re overlooking something.
The value of easy training may depend as much on what it allows us to recover from—and prepare for—as on the adaptations it produces directly.
This is particularly relevant for experienced athletes.
For a developing cyclist, increasing low-intensity volume may produce substantial improvements in aerobic capacity.
For someone with a decade or more of consistent endurance training, the additional benefit from another five hours of similar riding may be considerably smaller.
The training still produces physiological stress.
It still requires energy.
It still contributes to cumulative fatigue.
But its marginal adaptive benefit may be diminishing.
That changes the calculation.
Instead of asking:
How much Zone 2 can I accumulate before I begin serious training?
Perhaps we should ask:
How much aerobic conditioning do I actually need to preserve the qualities that allow me to respond exceptionally well when serious training begins?
These questions lead to very different training programs.
And they challenge the increasingly popular assumption that more endurance training necessarily produces a higher eventual performance ceiling.
The problem with confusing training load and fitness
TrainingPeaks has made concepts such as chronic training load, acute training load, and training stress balance familiar to endurance athletes.
These metrics are useful.
They provide a way to quantify accumulated training stress and understand how workloads change over time.
But they can also encourage an unfortunate interpretation.
That accumulating more training load means accumulating more physiological fitness.
The two are related, but they are not interchangeable.
An athlete can increase chronic training load while becoming progressively more fatigued.
They can maintain a high training load while experiencing little additional adaptation.
And they can sometimes produce outstanding performances after substantially reducing training volume.
This is not surprising when viewed through the fitness–fatigue model.
Training creates both positive adaptations and temporary negative effects.
Performance reflects the interaction between them.
The challenge is that those effects operate on different timescales.
Some adaptations develop relatively slowly and persist for extended periods.
Others change more rapidly.
Fatigue can disappear quickly, but certain forms of accumulated stress may take longer to resolve.
Consequently, two athletes with similar recent training loads may arrive at a workout with very different capacities to perform and adapt.
Even the same athlete may respond differently to an identical workout depending on the fatigue accumulated during the preceding weeks.
This raises an intriguing possibility.
An athlete who begins a demanding training block slightly less fit but substantially fresher may adapt more effectively than an athlete who begins with higher measured fitness but significant accumulated fatigue.
Not always.
And not indefinitely.
If conditioning falls too far, the athlete may lack the capacity to tolerate demanding training.
But somewhere between excessive detraining and excessive preparation lies a balance that conventional base-building discussions rarely address directly.
I would call this the conditioning–freshness balance.
The objective isn’t simply to maximize fitness before the build.
It’s to maximize the athlete’s readiness to benefit from the build.
The masters athlete: When the cost of training becomes more important
This question becomes particularly relevant with age.
Masters athletes often bring something younger competitors cannot easily replicate.
Years—sometimes decades—of accumulated endurance training.
Their cardiovascular and muscular systems have repeatedly adapted to substantial training demands.
They have developed technical efficiency, pacing ability, muscular endurance, and experience managing demanding efforts.
Many have already reached levels of aerobic conditioning that would require years for a younger, less experienced athlete to develop.
But aging also changes the equation.
Maximal aerobic capacity generally declines with age, while maintaining muscle mass, strength, and high-intensity exercise capacity becomes increasingly important.
Recovery can become more complicated.
Sleep, injury history, work stress, and the cumulative demands of training all influence how much additional stress can be tolerated.
This doesn’t mean masters athletes should avoid hard training.
Quite the opposite.
Maintaining appropriately challenging training may be particularly important for preserving high-level performance.
But it suggests that the separation between meaningful training stress and recovery may need to become more deliberate.
Perhaps the experienced masters athlete doesn’t need less intensity. Perhaps they need less unnecessary intensity.
And less unnecessary fatigue.
There is an important difference.
A demanding VO₂max session may provide a clear physiological stimulus.
A controlled threshold session may produce a valuable adaptation.
But a series of moderately demanding endurance rides between those sessions may add enough cumulative stress to compromise the quality of both.
The individual rides may feel manageable.
Yet the overall training program becomes increasingly expensive.
This leads to a form of polarization that extends beyond simply dividing workouts into easy and hard.
Polarizing the season, not just the workouts
Stephen Seiler’s research helped popularize polarized training.
In its conventional form, polarized training emphasizes substantial time below the first physiological threshold, relatively limited time between the first and second thresholds, and a smaller amount of high-intensity training above the second threshold.
The appeal is straightforward.
Athletes accumulate meaningful aerobic volume while preserving the ability to execute demanding sessions.
However, research comparing polarized and pyramidal training shows that neither distribution is universally superior across all performance outcomes and populations.
The appropriate distribution depends on the athlete, the event, and the stage of preparation.
But I think polarization has a broader application that deserves consideration.
What if we polarized the season itself?
Rather than attempting to maintain consistently high fitness and training stress throughout the year, perhaps we should create greater contrast between periods of preparation, development, consolidation, and competition.
Not every month needs to produce substantial gains in threshold power.
Not every training block needs to increase chronic training load.
And not every period of reduced intensity needs to be replaced with additional endurance volume.
An athlete might deliberately spend several months maintaining sufficient conditioning while keeping fatigue relatively low.
Then, during a more concentrated developmental period, they introduce progressive threshold training, VO₂max work, and race-specific intensity.
Because they begin that period well-conditioned and relatively fresh, they may be able to perform the demanding sessions at a higher quality and recover from them more effectively.
The process could produce a rapid increase in performance.
Eventually, improvements slow.
The athlete consolidates those adaptations, reduces training stress, and prepares for the next targeted period.
This is not conventional polarized training-intensity distribution.
It is closer to periodizing the balance between conditioning and recovery across the season.
And that distinction may be more important than whether an athlete spends 75% or 85% of their riding time below LT1.
What does the research actually tell us?
One particularly interesting finding comes from a 2024 systematic review and meta-analysis published in Sports Medicine.
The researchers compared polarized training with other endurance-training distributions.
Across 17 studies involving 437 participants, polarized training showed a small overall advantage for improving peak oxygen uptake.
More interestingly, that advantage was most apparent in interventions lasting fewer than 12 weeks and among highly trained athletes.
For longer interventions, the advantage was not demonstrated.
Other performance measures, including time-trial performance, time to exhaustion, and power or speed at the second physiological threshold, generally improved similarly across training distributions.
These findings are intriguing.
They suggest that concentrated periods of polarized training may be particularly effective for improving aerobic power in highly trained athletes.
But they don’t prove that an athlete should spend months doing minimal training before beginning an eight-to-twelve-week build.
Nor do they demonstrate that adaptations inevitably plateau after twelve weeks.
A separate individual-participant-data meta-analysis published in 2025 found no statistically significant overall difference between polarized and pyramidal training for VO₂max or time-trial performance, although athlete training status appeared to influence the response.
The research therefore supports a more nuanced conclusion.
Training distribution matters.
Training history matters.
The duration of the intervention matters.
And there is no single distribution that guarantees superior adaptation for every athlete.
Perhaps the most important unanswered question is not which intensity distribution is universally best.
It’s whether the physiological state in which an athlete begins a training block influences the effectiveness of that block as much as the training itself.
That seems particularly worth investigating in experienced masters athletes.
The minimum effective dose: What are we actually trying to maintain?
Another useful perspective comes from research into the minimum training required to maintain physical performance.
A 2021 review by Spiering and colleagues examined how reducing training frequency, volume, and intensity affected endurance and strength maintenance.
The authors found evidence that endurance performance could be maintained for several weeks despite substantial reductions in training volume, provided sufficient intensity was retained.
However, they also acknowledged that evidence was insufficient to establish precise minimum-dose prescriptions for competitive athletes.
This distinction matters.
Maintaining fitness is not the same physiological task as developing fitness.
The amount of training necessary to preserve an existing adaptation may be substantially smaller than the amount required to develop it.
For an experienced athlete, this opens an interesting possibility.
Perhaps the preparatory season should emphasize the minimum effective dose required to maintain the aerobic qualities that are most important for the next phase.
Not minimal exercise.
Not inactivity.
But enough training to preserve the foundation without unnecessarily compromising freshness.
Some longer endurance riding may remain essential, especially for athletes preparing for long events.
Occasional high-intensity exposure may help preserve aerobic power.
Strength training may address qualities that become increasingly important with age.
And carefully controlled threshold work may be useful when sustainable power begins to decline.
But the objective is maintenance and preparation, not continuous maximization.
This is where the traditional notion of base training begins to look different.
Instead of maximizing volume, perhaps the objective is to maintain the greatest practical amount of relevant conditioning at the lowest sustainable fatigue cost.
My own experience: The difference between being fit and being ready to improve
This question has become increasingly relevant as I’ve examined my own training history.
I’ve spent years racing and accumulating substantial cycling volume.
I’ve demonstrated strong aerobic capacity, high sustained power, and the ability to perform demanding efforts deep into long races.
Yet I’ve repeatedly noticed an interesting pattern.
Following periods of reduced training, my ability to produce reasonably high power often remains surprisingly strong.
More importantly, when I begin introducing structured high-intensity training, performance can improve rapidly.
During one recent winter, I spent November and December accumulating predominantly aerobic training.
When I introduced a relatively small number of VO₂max-oriented efforts, my short-duration power improved substantially within several weeks.
Efforts that had initially been difficult became manageable at significantly higher outputs.
Soon afterward, I was also producing strong sustained power.
But the progression didn’t continue indefinitely.
Illness interrupted training, and subsequent attempts to resume substantial work were accompanied by inconsistent performance and unusually demanding sweet spot sessions.
When I returned to a lower-stress approach and later reintroduced targeted intensity, performance improved again.
There are obvious limitations to drawing conclusions from this experience.
Illness is an important confounding factor.
Power-duration modeling does not directly measure physiological thresholds.
And a rapid improvement in two-to-five-minute power does not necessarily indicate a proportional increase in VO₂max.
Nevertheless, similar patterns have appeared across multiple seasons.
When I begin demanding training relatively fresh, I often respond quickly.
When I continue accumulating substantial training stress after progress has slowed, the additional work seems increasingly costly.
This has made me question whether my historical limitation has been insufficient endurance training—or insufficient separation between development and recovery.
Perhaps I’ve sometimes spent too much time trying to maintain high fitness and too little time preserving the capacity to improve it.
That is a hypothesis, not a proven physiological diagnosis.
But it’s one worth taking seriously.
Why improving threshold early may not always be useful
Consider an athlete whose primary championship occurs in August.
They begin November with a well-developed aerobic foundation and a threshold power somewhat below their best competitive level.
They could immediately begin a substantial threshold-development block.
Over the following eight weeks, sustainable power improves.
The workouts are productive.
Fitness rises.
But what happens next?
If the athlete wishes to retain that elevated level until August, they must continue providing sufficient training stimulus.
They may shift emphasis, reduce the threshold dose, or introduce different intensities.
Some adaptations will persist.
Others may decline.
Meanwhile, the athlete still has months of preparation remaining.
The problem isn’t that early threshold development is inherently wasted.
Some adaptations are durable, and early development can provide a foundation for later improvements.
The question is whether pursuing those gains early produces a better championship performance than preserving greater freshness and concentrating the development closer to competition.
For an athlete who responds slowly to threshold training, early development may be essential.
For an athlete who repeatedly demonstrates rapid improvement after reintroducing intensity, the answer may be different.
The latter athlete may benefit from delaying the most demanding developmental work until there is a clear competitive reason to perform it.
This is a crucial distinction.
The right training stimulus performed at the wrong time may still be the wrong training decision.
And there is no physiological requirement to maximize every trainable quality throughout the entire year.
Does more base actually produce a higher peak?
This brings us to the central question.
Traditional base-building logic often assumes that increasing aerobic conditioning creates a larger foundation for subsequent performance.
There is considerable truth to this.
Aerobic conditioning supports energy production, fatigue resistance, recovery between efforts, and tolerance of repeated training.
For developing athletes, greater endurance capacity can substantially improve future performance.
But the relationship may not remain linear forever.
At some point, additional endurance training may produce smaller gains.
Meanwhile, its fatigue cost continues.
For a highly trained athlete, the question becomes one of diminishing returns.
Suppose one cyclist begins a demanding training block with slightly greater aerobic fitness but substantial accumulated fatigue.
Another begins with marginally less aerobic fitness but considerably better recovery status.
Which athlete will produce the better response?
We cannot answer that question universally.
The first athlete may possess greater workload tolerance.
The second may execute demanding sessions more effectively.
The outcome will depend on the size of the fitness difference, the amount of fatigue, and the nature of the upcoming training.
But this is precisely the trade-off that deserves more attention.
The highest possible starting fitness is not necessarily the starting condition that produces the highest eventual peak.
What we want is the greatest possible adaptable fitness.
Enough conditioning to tolerate the work.
Enough freshness to benefit from it.
And enough time for the resulting adaptations to develop before competition.
A different model: Conditioning without unnecessary fatigue
If we accept this possibility, the preparatory season begins to take on a different purpose.
Rather than treating it as a prolonged period of progressively increasing training load, we can view it as a period of preserving and selectively improving the qualities that support subsequent development.
For an experienced endurance athlete, that may involve four objectives.
Preserve the aerobic foundation
Maintain sufficient endurance work to retain cardiovascular conditioning, metabolic efficiency, and event-relevant durability.
The amount required will depend on the athlete and event.
A cyclist preparing for a five-hour road race requires different preparation from someone targeting a short time trial.
But the objective is not automatically to increase volume every week.
Maintain exposure to demanding intensities
Avoid allowing high-intensity capacity to disappear entirely during extended preparatory periods.
Occasional targeted sessions may preserve important physiological and neuromuscular qualities without creating the fatigue associated with a full developmental block.
The exact dose must be individualized.
Develop qualities that are difficult to address during competition
Strength, mobility, movement efficiency, and musculoskeletal resilience may deserve greater attention when racing demands are lower.
These adaptations can support later training.
But strength work also creates fatigue and must be included in the total recovery calculation.
Protect the capacity to recover
This is the defining objective.
The preparatory period should leave the athlete increasingly capable of absorbing demanding training.
Not progressively exhausted by the attempt to build an ever-larger aerobic base.
In practical terms, this could mean accepting a lower chronic training load, more genuinely easy riding, and less pressure to continually improve threshold power during the off-season.
For some experienced athletes, that may be exactly what is needed.
For others, particularly those with insufficient aerobic conditioning, a more substantial base-building period will remain appropriate.
The objective is not to replace one universal prescription with another.
It’s to make the preparatory phase serve the athlete rather than the training model.
The 12–16-week hypothesis
My own experience has led me toward a particular working hypothesis.
For an experienced, well-conditioned athlete, a concentrated period of approximately 12–16 weeks may be sufficient to develop a substantial amount of race-relevant fitness—provided the athlete begins that period appropriately conditioned and recovered.
That doesn’t mean every physiological adaptation occurs within sixteen weeks.
Nor does it mean additional training becomes ineffective afterward.
It means that the most productive period of focused development may be shorter than the traditional model assumes.
During the early weeks, threshold power and high-intensity capacity may improve rapidly.
As training progresses, adaptation continues but may become more difficult to distinguish from accumulating fatigue.
Eventually, the athlete may reach a point where maintaining the training stimulus produces diminishing improvements.
That is where the balance should shift toward consolidation, recovery, and competition.
The objective is not to train hard until performance begins declining.
It’s to recognize the point at which continuing to increase stress is no longer the most productive strategy.
This creates a different annual structure.
A substantial preparatory period focused on conditioning and freshness.
A targeted developmental period that progressively introduces demanding work.
A period of competition and consolidation.
Then, when the calendar requires it, another focused development block.
Rather than continuously trying to maximize fitness, the athlete deliberately creates opportunities for fitness to rise.
The objective is not to remain near peak condition for ten months. It’s to create the conditions that make a higher peak possible when it matters.
Why this may matter more as we age
There is a temptation to assume that aging athletes should simply train less.
I don’t think that captures the issue.
Highly trained masters athletes still require meaningful physiological stress to maintain and improve performance.
Indeed, insufficient exposure to higher intensities may contribute to the decline in aerobic power that occurs with age.
But perhaps aging increases the importance of precision.
The difference between productive and unnecessary training stress becomes increasingly consequential.
A hard workout should create a meaningful stimulus.
An easy workout should support conditioning without compromising recovery.
A recovery period should actually reduce fatigue.
And an entire preparatory season should create the conditions needed for the next developmental phase.
This is where I see a broader version of polarization becoming useful.
Not simply an 80/20 distribution of training intensity.
But a deliberate separation between periods when we are trying to create substantial adaptation and periods when we are primarily trying to preserve it.
For an experienced masters athlete, that may prove more useful than continuously pursuing greater training volume.
The paradox: Sometimes less preparation may allow more improvement
There’s a counterintuitive possibility at the heart of this argument.
Two athletes can begin a structured training block with different levels of measured fitness.
The athlete with higher fitness may not necessarily possess the greater opportunity for improvement.
If they have already spent months accumulating substantial training stress, their ability to tolerate further increases may be limited.
The slightly less fit athlete, provided they retain adequate conditioning, may be able to absorb a more effective progression of demanding training.
They may improve more rapidly.
They may tolerate higher-quality sessions.
And they may arrive at competition with a better combination of performance capacity and freshness.
That is the freshness paradox.
Reducing training stress during preparation can appear to sacrifice fitness in the short term.
Yet, under the right circumstances, it may create the conditions for a greater increase in performance later.
We should be careful not to exaggerate the principle.
Freshness is not a substitute for training.
Rest does not create aerobic capacity by itself.
And experienced athletes can lose important adaptations if training is reduced excessively or for too long.
But the opposite is equally important.
More training does not automatically produce more adaptation when the athlete is no longer recovering sufficiently to benefit from it.
The optimal preparatory workload may therefore be neither the maximum tolerable workload nor the absolute minimum.
It may be the workload that preserves the greatest amount of relevant conditioning while leaving the athlete best prepared to absorb the next phase.
Rethinking the purpose of base training
Perhaps the term base training has become too closely associated with volume.
We measure how many hours we ride.
How much time we accumulate below LT1.
How much training stress we generate.
And how consistently we increase those numbers.
But the purpose of a base is not to create impressive training statistics.
It is to support what comes next.
For a developing endurance athlete, that may require substantial additional aerobic development.
For an experienced athlete, it may require far less development and considerably more attention to fatigue management.
In both cases, the objective should be the same.
To enter the demanding phase of training with the greatest possible capacity to adapt.
This shifts the question from:
How much aerobic training can I accumulate before the season begins?
To:
What amount and type of training will leave me best prepared to absorb the work that determines my peak performance?
That is a more individualized question.
And I suspect it may lead experienced athletes toward substantially different preparatory programs than the conventional pursuit of ever-increasing endurance volume.
Final thoughts: Build the capacity to adapt
I still believe aerobic conditioning is fundamental to endurance performance.
I still believe threshold development matters.
And I certainly believe that high-intensity training is necessary to reach the highest levels of competitive performance.
What I’m increasingly questioning is the assumption that these qualities must be developed continuously—or that maximizing the amount of aerobic training before introducing intensity necessarily produces the highest eventual peak.
The training history of an experienced athlete matters.
The timing of adaptation matters.
The cumulative cost of training matters.
And the physiological condition in which an athlete begins a demanding block may matter more than we currently acknowledge.
Alan Couzens provides a compelling framework for sequencing endurance adaptations.
Phil Maffetone and Mark Allen demonstrate the importance of controlling training stress and allowing aerobic development to occur without constantly pushing intensity.
Stephen Seiler’s work highlights the value of separating substantial low-intensity training from demanding sessions.
Each offers part of the picture.
But perhaps the next step is to think beyond the distribution of intensity within a training week.
Perhaps we need to consider how we distribute the demand for adaptation across an entire season.
For experienced athletes, especially masters competitors, the objective may not be to maintain the highest possible level of fitness year-round.
It may be to preserve enough fitness, strength, and durability that we can enter a concentrated developmental period fresh, responsive, and capable of absorbing substantial training stress.
Because ultimately, the goal isn’t to maximize the training we complete.
It’s to maximize the adaptation we obtain from it.
And perhaps the best base isn’t the one that leaves us the fittest in February.
It’s the one that leaves us best prepared to become the fittest we’ve ever been in August.
Research and further reading
Alan Couzens — Seasonal Training Progression and Individualized Development
Couzens’ published framework outlines the progression from general aerobic preparation through threshold, VO₂max, and race-specific training. His later writing also emphasizes differences in individual training responses.
https://alancouzens.com/TP/templates/season.html
https://alancouzens.substack.com/p/what-type-of-athlete-are-you
Phil Maffetone — Interview with Mark Allen (2015)
A retrospective discussion of aerobic development, managing physiological stress, and integrating higher-intensity training.
Seiler, S. (2010). What Is Best Practice for Training Intensity and Duration Distribution in Endurance Athletes?
International Journal of Sports Physiology and Performance, 5, 276–291.
https://pubmed.ncbi.nlm.nih.gov/20861519
Silva Oliveira, P., Boppre, G., & Fonseca, H. (2024). Comparison of Polarized Versus Other Types of Endurance Training Intensity Distribution on Athletes’ Endurance Performance: A Systematic Review with Meta-analysis.
Sports Medicine, 54, 2071–2095.
https://pubmed.ncbi.nlm.nih.gov/38717713
Which Training Intensity Distribution Intervention Will Produce the Greatest Improvements in Maximal Oxygen Uptake and Time-Trial Performance in Endurance Athletes? (2025).
Individual-participant-data systematic review and network meta-analysis.
https://pubmed.ncbi.nlm.nih.gov/39888556
Spiering, B. A., Mujika, I., Sharp, M. A., & Foulis, S. A. (2021). Maintaining Physical Performance: The Minimal Dose of Exercise Needed to Preserve Endurance and Strength Over Time.
Journal of Strength and Conditioning Research, 35, 1449–1458.
https://pubmed.ncbi.nlm.nih.gov/33629972
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