Shownotes

How many hours to reach full aerobic capacity

02:56 -

• Carson's answer, perhaps surprisingly given how often coaches reach for "it depends," is 10,000 hours. He draws on Malcolm Gladwell's well-known rule but grounds it in more recent research, specifically the Sandbeck 2025 paper on best-practice training characteristics from the Norwegian Federation.
• Looking at how elite Norwegian athletes' careers have developed, with annual training loads ranging from 600 to 1,200 hours and peak performances arriving after eight to twelve years, the 10,000 hour figure holds up reasonably well.
• My own take is that 10,000 hours is probably right if we're talking about reaching absolute genetic potential.
• Anecdotally, getting to an Olympic final in events like swimming or track and field tends to follow eight to ten years of structured training, with the total hours varying by event.
• For something like the 5,000 or 10,000 metres, you're likely approaching that figure; shorter events somewhat less so.
• For most listeners, though, the more practical question is how many hours it takes to reach around 95% of your potential, the point where you are performing at a genuinely high level and looking for marginal gains rather than fundamental development.
• Looking at my own data, I believe I reached that point at somewhere around 4,500 to 6,000 hours. My TrainingPeaks records go back to 2016, and by 2021 I had logged around 3,500 hours of swim, bike and run.
• Adding in the training from the years prior, where I was less consistent and had only started endurance sport six or seven years before that point, I would put my personal number at perhaps 4,500 to 6,000 hours as a conservative estimate.

The 10,000-hour rule

06:59 -

• One thing worth observing is that the sport is getting younger. Peak performances in Ironman and across the age group spectrum are now coming from athletes in their mid-to-late twenties, and the speeds being produced by younger amateurs in the 25 to 35 bracket are exceptional.
• Part of what is driving this is that we are now seeing athletes who have grown up in triathlon from the beginning, rather than coming from a single-sport background like swimming or water polo and transitioning later, as was common in earlier generations.
• For an age grouper who did not have an endurance background growing up, a figure closer to 5,000 hours to reach a high level of personal development remains entirely plausible, and it sets the stage well for how long-term development can be structured effectively within a single training year.

Adult-onset athletes and training

08:52 -

• The conversation shifts to what this means for athletes who come to the sport as adults. Not everyone is Kristian Blummenfelt, and a top-down approach drawn from elite development simply does not apply to someone who picks up triathlon in their early thirties or forties.
• The key variables are how many years they can realistically commit to the sport, the financial demands it places on them and their families, and what their actual end goal is, whether that is short course, long distance, or something in between.
• The honest answer is that you have to make the timeline extremely clear from the outset.
• Athletes regularly come in wanting to qualify for Kona within a year, and while that is possible for some depending on genetics and circumstance, the more common reality is that it takes three, four, or five years of patient, progressive development.
• Chasing large wins in a short window almost always works against the long-term process.
• For self-coached athletes, the challenge is knowing how much training is appropriate and staying honest with themselves about it. AI tools can get someone a reasonable part of the way there, but the real risk for self-coached athletes is the ego-driven tendency to push just a little further than they should.
• Having a local coach, a peer, or even a single-sport mentor to bounce ideas off of provides a useful check on that impulse, because the consequences of overshooting, whether through injury, illness, or accumulated fatigue, set the long-term development back considerably.
• On the question of whether athletes more commonly do too much or too little, undershooting is rare. Triathlon attracts type A personalities, and the default error has historically been too much intensity, too many hard days, or too much time in the gray zone between easy and genuinely hard.
• What is interesting now is a shift in the other direction driven by social media, with many athletes swinging to exclusively zone two training regardless of their total weekly hours. That extreme carries its own limitations, because too much easy volume without sufficient intensity stimulus also stalls development.
• The deeper pattern here is that as a species we gravitate toward extremes because extremes feel like a competitive edge, a secret formula that others are missing. One season it is all sweet spot; the next it is all zone two.
• What consistently falls out of fashion is a balanced approach, not because it does not work, but because nuance does not go viral.
• The content that spreads is the content that makes a bold, simple claim, and so the balanced middle ground remains perpetually underrepresented in what most athletes actually see.

Structuring intensity in training

15:42 -

• The broadly accepted answer, consistent with what most coaches and practitioners point to, is around two intensity sessions per sport per week for a healthy, fit athlete at an appropriate point in their training cycle.
• The important qualifier is how intensity is defined: for these purposes, it means anything above the first lactate turn point, not just VO2 max or maximal threshold work. That framing matters because it captures a wider range of sessions than athletes typically account for.
• In practice, some weeks do not reach two intensity sessions per sport per day if sessions are doubled up. A hard swim and a hard run on the same day, for example, might mean removing another intensity session later in the week to allow the tissues and metabolism to recover properly.
• On the question of stacking versus spreading, the preference here leans toward one genuinely hard effort per day, with supplemental easier work alongside it.
• The underlying principle is that what you did yesterday is just as important as today, which is in turn just as important as tomorrow. Everything works together across the week.
• A hard run on Tuesday morning might be paired with an easy swim or bike that same day, giving the athlete just over 24 hours of recovery before they can then complete a harder session in the pool or on the bike on Wednesday afternoon.
• The harder sessions are rarely the problem. Most athletes have no difficulty going hard when the session calls for it. The issue is that easy training keeps creeping upward.
• There is no compelling research showing you can go genuinely too easy, other than in extreme cases where the effort is so low it produces no meaningful stimulus, but in practice almost everyone pushes their zone two rides, runs, and swims just a little harder than they should, either to accumulate a fitness gain or, more subtly, to avoid feeling like the session was wasted.
• That said, I have seen athletes whose easy training is actually too easy, though this is less common and tends not to show up much in swimming, where the focus is more technical than metabolic anyway.
• A lot of endurance training ends up sitting in high zone one or very low zone two without being prescribed to be there, and in many cases athletes arrive with a miscalibrated sense of what easy and hard actually feel like.
• Whether slightly too easy is a problem also depends heavily on total training volume: someone doing 20 hours a week operates under very different constraints than someone doing 10, and the threshold for what constitutes productive easy work shifts accordingly.
• The practical version of this is something coaches see regularly. An athlete runs what they describe as an easy marathon or half marathon pace, averages something like 4:45 per kilometre, and comes in with a heart rate of 160.
• Without a coach pointing out that they could afford to slow down, they will simply report it as an easy session and move on. Over time, that cumulative creep upward erodes the contrast between easy and hard, and with it the headroom needed to build toward later in a long-term development plan.

Age and training considerations

25:55 -

• With a younger athlete, the body is more flexible, recovery is faster, and there is simply more room to work with.
• The priority becomes understanding how much they can realistically train given their life circumstances, whether that is a demanding job, a young family, or other commitments, and then finding a progressive range to build from.
• Younger athletes can generally tolerate a higher intensity load alongside volume growth, so the work becomes a back-and-forth calibration of where to place the emphasis.
• With an older onset athlete, the approach shifts considerably. Volume is not the starting point. The priority is finding a path that fits their life, keeps them healthy, and incorporates enough rest and body maintenance work to make consistent training sustainable.
• Jumping straight to a volume-first model for a newer athlete in their fifties is a mistake.
• My view on this is that the return on volume investment is genuinely high in your twenties and thirties, and then it gradually tapers with each decade.
• By the time someone is starting in their fifties, their absolute potential ceiling is lower than it would have been earlier, which means they are probably already closer to it.
• The calculus shifts: you can achieve meaningful results with less volume, but the limiting factors become things like muscle strength, muscle power, and VO2 max, which degrades more rapidly than other markers of endurance performance as we age.

Volume and intensity according to the athlete’s age

29:26 -

• For older onset athletes, the emphasis on intensity shifts toward the pool and the bike and away from the run. The reasoning is straightforward: running intervals carry a higher musculoskeletal and fascial injury risk, and for athletes whose speed potential is already more limited, the return on high-intensity running is lower.
• The goal in running becomes more about not slowing down across the long distance rather than developing top-end speed. In the pool and on the bike, intensity can be applied more freely without the same injury exposure.
• For younger athletes, the distribution looks different. There is more latitude to develop speed on the run alongside the bike, while swimming shifts toward technique and durability as the primary focus, even as raw swim speed remains an objective.
• Across all ages and all disciplines, the overriding priority is keeping the athlete healthy and training consistently. Everything else follows from that.

Which Discipline Rewards Aerobic Volume Most?

31:30 -

• The bike offers the greatest return on aerobic volume investment across triathlon. It is admittedly the most time-consuming and logistically demanding discipline depending on where you live and the terrain available, but the aerobic benefit it produces relative to the other two is the highest.
• After that, swimming. That view does not come purely from a collegiate swimming background, but from consistently observing that a strong aerobic base built in the water translates into better running without requiring an equivalent increase in run volume or intensity.
• Swimming carries a particular advantage for younger athletes in this regard.
• When you are young and recovering well, you can absorb a level of combined volume and intensity in the pool that would break most runners.
• It is not necessarily the most optimised approach, but it is an effective one: accumulating large training loads in a low injury-risk environment, and having those aerobic gains carry over to the run and the bike.
• The sport is now moving toward shorter, more intense swim programs with a greater emphasis on strength and force production, which reflects broader trends in how swimming is coached, but the aerobic case for high swim volume remains strong.

Youth training vs. adult development

35:05 -

• The flip side of throwing volume and intensity at young athletes is the attrition it produces. 
• Cycling is a vivid example: riders in their early to mid-twenties are now winning the Tour de France and the monuments, but behind each of those champions are enormous numbers of young athletes who have been broken before they ever reached their peak.
• For a federation or a commercial team, that trade-off may be acceptable. For any individual athlete trying to get the most out of themselves, those odds are not attractive.
• This scales directly to amateur triathlon. An athlete who races hard every weekend, never allowing for genuine development phases, is essentially accumulating a false version of the 10,000 hour rule: the hours are there, but the adaptive stimulus is not.
• The same pattern is visible in youth football in the United States, where young players play competitive matches year-round but never develop the underlying sport-specific skills because they are always in performance mode rather than development mode.
• Applying that to older age group triathletes: going hard constantly, without the boring foundational training in between, reduces the chance of ever reaching a genuine aerobic peak. Having at least one meaningful race goal per year is still important, but structuring an entire year around a single event with no racing at all creates its own problems.
• The Norwegian sporting model illustrates what a long-term alternative looks like. Across multiple sports, including football where Norway now punches well above its historical weight, their system is built around keeping athletes in the game as long as possible rather than extracting short-term results from young competitors.
• One concrete expression of this is eliminating or significantly delaying national championship competition for younger age groups.
• When a 13-year-old is being prepared to peak for a national title, the training decisions made in service of that goal actively work against long-term development.
• Early maturing athletes get selected and celebrated, while the athletes who will ultimately prove most talented are filtered out before they have had the chance to develop.
• The same dynamic appears in junior ice hockey, where junior world championships receive enormous attention despite the fact that players at that age have not yet reached physical maturity, and early physical developers will consistently outperform those who mature later but may ultimately be the better players.
• The competitive structure itself distorts the talent identification process.
• The broader principle, whether in elite youth sport or amateur triathlon, is that short-term competitive pressure and long-term development are frequently in tension, and defaulting to the former at the expense of the latter is a trade-off that rarely serves the individual athlete well.

Planning year-on-year progression

43:13 -

• Documenting how training volume evolves over time and tracking whether things are generally moving in the right direction is always worthwhile.
• That said, life rarely allows for rigid multi-year plans, and there are plenty of athletes who never substantially increase their annual hours yet continue to improve, whether through better intensity management, improved recovery, or simply greater consistency.
• The more reliable level to manage is the microcycle: getting the weekly and monthly structure right tends to take care of longer-term progression naturally.
• The 10% rule is a useful starting point, though it can be bent somewhat when the additional volume comes primarily from swimming and cycling rather than running, given the lower musculoskeletal loading those disciplines carry.
• The more important principle is preserving room to continue growing in subsequent years. Jumping from 500 to 900 hours in a single year may be physically manageable in the short term, but it compresses the progression curve and leaves less to build on in year two or three.
• The exception is when life circumstances change substantially, such as a sabbatical from work that frees up large amounts of training time.
• In that case, a more aggressive increase on the bike and in the pool is reasonable, provided run volume is increased more conservatively to allow connective tissue and structural resilience to adapt at the pace they require.

Measuring progress: tests and metrics

46:20 -

• Lactate testing comes in and out of fashion, and if an athlete is genuinely interested in it and the cost and logistics are manageable, it has its place. 
• But it is not something worth pushing on athletes for whom the time and expense are not justified by their training volume or goals.
• For field testing, the standard 20-minute FTP test has largely been set aside in favour of critical power tests across three or four durations.
• The multi-duration approach is less mentally demanding for the athlete, produces a richer picture of where they sit across the power curve, and can be repeated a few times a year without the psychological weight that a single maximal effort tends to carry.
• Alongside those structured tests, sub-maximal spot checks at more or less arbitrary durations serve as useful ongoing checkpoints, tracking the relationship between heart rate, perceived effort, and power or pace over time as a way of monitoring adaptation without requiring a full testing block.

Sub-maximal testing in practice

47:50 -

• In practice it might be a 30-minute time trial held at a four or five out of ten effort, or a block ridden within a known Ironman heart rate range.
• Fatigue resistance is a concept that gets a lot of attention now, and one useful format is accumulating a set amount of work, say 2,000 to 3,000 kilojoules on the bike, and then completing a 45-minute sub-maximal effort at around Ironman pace. 
• The Maffetone heart rate approach still has a place here as one more modelling data point. The broader point is that in long-course triathlon specifically, there are more meaningful markers of progression than a five-watt improvement in threshold power.
• Threshold changes below around ten watts are close enough to day-to-day variation that drawing conclusions from them is unreliable. Athletes may be improving significantly in other areas while that number barely moves.
• Sub-maximal testing is genuinely useful, but it carries its own uncertainty. If you control by heart rate and track power or pace, you need to account for whether that heart rate is suppressed by accumulated fatigue.
• RPE adds context, but when an athlete knows they are being tested, their perceived effort is likely to be influenced by wanting to see improvement.
• The closer a sub-maximal test pushes toward the hard end of the spectrum, the more reliably you can detect real changes in fitness. The pre-fatigued format addresses this well, particularly for athletes targeting long-distance events.
• That is also where the art of coaching enters the picture. How a test is framed and where it is embedded in a workout matters enormously.
• Type A athletes, which describes most triathletes, will start mentally preparing the moment they see the words "FTP test" or "time trial" in their plan.
• Structuring testing efforts within training in a way that removes or reduces that psychological loading produces more representative data. It is also, frankly, one of the areas where AI-based coaching is unlikely to close the gap anytime soon.
• Every AI training tool has been trained on content that tells it to test, when to test, and which test to use. The judgement around how to embed an assessment invisibly within a training week, and the language used to frame it, is something that remains firmly in the domain of human coaching.
• Related to this, one pattern that has come up with athletes arriving from certain AI training platforms is a compulsion to test constantly, sometimes every four to six weeks throughout the entire year.
• That frequency, sustained year-round, is enough to burn out the neuromuscular system and leave an athlete's best efforts in testing rather than racing.
• A structured testing block in the winter, perhaps two or three assessments spaced eight weeks apart, is a very different proposition from repeating that cycle indefinitely.
• The same problem appears in some sport-specific online programs, including in swimming, where weekly testing has been prescribed despite the fact that adaptations simply do not accumulate fast enough to make that frequency informative.
• Testing too often does not accelerate development; it erodes it.

Racing as testing

54:00 -

• In triathlon specifically, it is difficult to expect peak efforts on race day in any meaningful data sense. The variables are simply too numerous.
• Single-sport efforts are a different matter: a standalone 5K, a swimming race, or a 20-mile time trial can produce genuinely representative best efforts.
• Interestingly, many athletes also record their best power and pace numbers early in the season, in February or March, before accumulated training fatigue sets in.
• Joel Filliol made this point in a post that drew considerable attention, warning against what he described as becoming "too fit" too early and developing a misleading sense of fitness that may not carry through to the races that matter.
• The core of Filliol's argument is straightforward: avoid forcing high-intensity efforts too early in the year, preserve room to build resilience progressively, and do not burn peak efforts on a January 5K.
• There was significant pushback and no shortage of jokes, but coaches with long track records of developing athletes over extended periods deserve more than a dismissive response. Reading between the lines matters here.
• That said, the context in which Filliol operates is important. He works primarily with elite or high-performing younger athletes competing at sprint and Olympic distance, where a traditional linear periodisation model, lower intensity and higher volume early, building to race-specific intensity later, is well suited.
• That model does not transfer directly to a 50-year-old preparing for an Ironman, nor to an amateur living in northern Finland or the American Midwest where winter daylight and temperatures impose real constraints on outdoor training volume.

Overcoming performance plateaus

58:30 -

• For that athlete, doing some harder efforts in the middle of winter, or chasing a parkrun personal best in late winter, is entirely reasonable.
• Their overall training load is nowhere near that of a world-class athlete, the psychological benefit of a small win in a dark January keeps motivation intact, and the physiological cost is manageable.
• The broader principle is that the Filliol argument is correct within its original context, and the debate that followed would have been more productive had that context been made explicit earlier.
• Whether a training philosophy is right or wrong is almost always the wrong question. The more useful question is: right for whom, and under what conditions.
• When I observe that an athlete has plateaued and is no longer improving, either in competition results or in training performance, I begin by analysing the training structure itself.
• I assess whether adjustments are required in terms of volume or intensity, always in the context of the athlete’s broader life constraints.
• I look for objective indicators such as stagnation in threshold values, paces, or specific performance benchmarks like 5 km or 10 km times, or time trial efforts in the pool.
• If these metrics are no longer progressing, I revisit the balance between training volume and intensity, considering whether one may be excessively high or insufficient relative to the other.
• Beyond the training prescription, I place significant emphasis on lifestyle factors, particularly sleep and nutrition.
• Although there is widespread awareness of their importance, I find that many athletes do not consistently apply this knowledge in their daily routines. It is common to see athletes executing well-structured sessions and meeting carbohydrate intake targets during exercise, yet compromising recovery through insufficient sleep.
• In such cases, I evaluate whether adjustments to daily structure are necessary, such as redistributing training sessions to better align with recovery needs. 
• The objective is to ensure that training interventions are supported by adequate recovery and overall well-being.
• I recognise that there is often a considerable gap between understanding the principles of performance optimisation and effectively implementing them.
• While nutritional adjustments can generally be addressed with relative ease, managing sleep and overall recovery is more complex, particularly for athletes balancing professional and personal responsibilities.
• Achieving a high level of performance requires navigating these trade-offs, and I view this as one of the most challenging aspects of the process. Reaching close to one’s true potential is rarely compatible with convenience, and it often demands deliberate compromises in other areas of life.
• In certain cases, particularly with older athletes who have demanding careers and family obligations, I acknowledge that maximising performance in the present may not be realistic. Instead, I consider the concept of training age and long-term development.
• While absolute physiological markers such as VO₂ max may decline over time, the athlete’s ability to reach their individual potential may actually improve later in life when more time and energy can be dedicated to training.
• This perspective shifts the focus from immediate peak performance to sustained progression over the long term.
• In this context, I sometimes adopt a more conservative approach, prioritising consistency and longevity over short-term gains.
• The objective becomes maintaining engagement in training, preserving both physical and mental readiness, and creating the conditions to pursue higher performance levels when life circumstances are more favourable.

Thing that Carson has changed his mind about

1:06:25 -

• As I have gained experience as a coach, my perspective has evolved significantly. Early in my career, I tended to rely heavily on performance data and observable results to guide decision-making.
• There was a tendency to assume that successful outcomes could be systematically reproduced through adjustments in training variables alone, which reflects a common early-stage overconfidence in purely analytical approaches.
• Over time, I have shifted towards a more comprehensive and contextual methodology. I now place considerably greater emphasis on the personal lives of athletes and on their subjective feedback.
• I actively seek to understand factors beyond training itself, recognising that performance is deeply influenced by lifestyle, environment, and individual circumstances.
• This includes gathering detailed information about daily routines, family structure, and time constraints, as these elements directly impact the feasibility and effectiveness of any training plan.
• In practice, this means that I no longer operate solely as a data-driven analyst but rather take on a broader role in supporting the athlete.
• I aim to integrate training within the realities of their life, aligning performance objectives with their personal context.
• By doing so, I can make more informed and sustainable decisions, ultimately contributing to the development of a more balanced and resilient athlete.

Practical pieces of advice

1:08:30 -

• The first principle I prioritise is thinking in terms of long-term consistency rather than short-term progress.
• I recognise that many athletes focus excessively on what they can achieve over the next eight to twelve weeks, often driven by upcoming tests or immediate performance markers.
• However, I place greater importance on what can be sustained and developed over several years. To make this approach actionable, I ensure that I understand my annual training volume.
• Rather than only tracking recent weeks or months, I look at the total number of hours accumulated over a full year, as this provides a much clearer picture of consistency and highlights the impact of interruptions such as illness, injury, or other life constraints.
• The second principle I follow is to prioritise building a solid physiological foundation before attempting to reach peak performance.
• I focus on progressively increasing the amount of training that I can consistently sustain, whether measured weekly, monthly, or across multiple years.
• I monitor how this progression translates into performance improvements, such as changes in pace, thresholds, or race outcomes.
• This allows me to assess whether I am moving in the right direction while acknowledging that peak performance is the result of a long accumulation of training rather than a short-term effort.
• I remain aware that true potential is often realised only after several years of structured and progressive development.
• Finally, I evaluate progress based on what is repeatable rather than what is momentarily impressive. Instead of relying on isolated peak efforts or singular standout performances, I focus on consistent indicators of progression that can be reproduced over time.
• This may include training volume, distance covered, or stable improvements in performance metrics.
• By doing so, I avoid the tendency to chase exceptional one-off results and instead ensure that my development is grounded in sustainable and measurable progression.

Sporting and non-sporting recommendations in Milwaukee

1:15:02 -

• From a sporting perspective, I see Wisconsin as an excellent destination for cycling, particularly in and around Madison.
• The area west of the city offers some of the best riding conditions I have encountered in the United States. While it does not feature long alpine-style climbs, the terrain is varied and engaging, with short climbs and constantly changing profiles.
• The road network is notably quiet and structured in a way that feels more reminiscent of European riding, avoiding the long, straight, uninterrupted roads that are common in many parts of the U.S.
• This creates a more dynamic and technically interesting riding experience, which is one of the reasons why the region has long hosted events such as Ironman Wisconsin.
• From a non-sport perspective, I would emphasise the food culture in Milwaukee and the surrounding region. Wisconsin has a strong culinary identity rooted in its dairy production, particularly cheese, but what stands out is the diversity of cultural influences.
• There is a significant presence of Polish and Scandinavian heritage, among others, which contributes to a varied and high-quality food scene.
• This combination of local produce and multicultural influence makes the region particularly interesting from a gastronomic standpoint.

LINKS AND RESOURCES

• Carson and Torden Multisport on Instagram
• Carson’s previous appearance on That Triathlon Show: The Trisutto Way of Triathlon Training with Carson Christen | EP#140