The Silent Effort

Performance does not break down first. Health does. Belgian cyclist and coach Toon Heirbaut reveals why so many athletes are training harder while actually becoming less capable, and what the right foundation looks like when you want both results and resilience.

If you have ever felt strong on paper but constantly sick, flat, or one hard session away from crashing, this conversation will hit home. 

Casper Hessellund and Toon unpack the hidden cost of stress, poor recovery, and bad fueling - and why the biggest mistake in endurance sport is often chasing more training instead of fixing the system underneath it.

You’ll discover: why stress is the real number one performance limiter, how to spot the earliest signs of under-recovery before your body fully breaks down, and why resting heart rate and HRV matter more than most athletes realize. Toon also breaks down the difference between being undertrained and under-recovered, how amateurs misread fatigue, and why elite athletes can tolerate more load simply because they carry less life stress off the bike.

We also get into nutrition and fueling strategy in a way most cyclists never hear. 

Toon explains when carbs should be pushed hard, when fat oxidation should be trained, why zone 2 is usually much lower than people think, and why “no testing, no training” is non-negotiable in his coaching philosophy. He shares why performance tests matter, how to use them to avoid the grey zone, and why the numbers often tell a very different story than your feelings do.

Sleep is another major piece of the puzzle, and Toon lays out the practical side of recovery: how cortisol and melatonin need to work together, what actually helps deep sleep, and why a consistent wake-up time can matter more than chasing a perfect number of hours. He also shares the morning routine he uses himself, including light exposure, movement, hydration, and focus work before training.

This is essential listening if you are an endurance athlete, coach, or ambitious amateur who suspects that the answer is not more discipline, but better management of stress, sleep, recovery, and mindset. By the end, you’ll have a much clearer view of what actually builds durable performance - and what quietly destroys it.

Casper Hessellund hosts Toon Heirbaut, a Belgian cyclist and coach who works with athletes on performance, recovery, and health after dealing with his own long stretch of illness and imbalance.

The reality of being a professional triathlete is about more than podiums, sponsors, and traveling the world. Behind the highlights are demanding training weeks, financial pressure, injuries, loneliness, and the mental challenge of continuing to perform when things don’t go to plan.

In this episode of the Silent Effort Podcast, Casper Hessellund talks with professional triathlete Valdemar about what it really takes to pursue elite endurance sport. Valdemar shares how he balances training with a part-time job and coaching, what a typical week of training looks like, and why building a career in triathlon can be financially uncertain, even for athletes competing at a high level.

They also get into the tough calls athletes face: when to keep pushing and when to stop, how to handle a DNF, and why training through pain isn’t always a sign of strength. Valdemar explains the importance of listening to your body, balancing performance data with your own instincts, and making smart decisions in the moment rather than blindly following a plan.

In this conversation, you’ll hear about:

- What a demanding triathlon training week can look like

- The financial realities of trying to make a living as a professional athlete

- The sacrifices elite sport can require from relationships and everyday life

- How to recognize the difference between soreness and pain that needs attention

- Why knowing when to ease off can be just as important as knowing when to push

- The mental pressure of racing against the best—and being close to the top without feeling there yet

- How trust, patience, and daily decisions help athletes keep moving forward

For Valdemar, triathlon is a decision sport: success depends not only on fitness, but also on the choices made in training, recovery, competition, and life. This is an honest conversation about the unseen work behind performance, and the grit it takes to keep chasing a goal that may still be just out of reach.

Fuel Smarter, Ride Faster: A Practical Guide to Endurance Fueling

Fueling is not a marginal gain, it can make or break your performance. Mathias returns to discuss how much to eat, what to eat, when to eat it, and why training your gut matters just as much as training your legs.

If you’ve ever bonked late in a race, felt too full at the start, or wondered why some riders can handle 120 grams of carbohydrates per hour while others struggle at 60, this conversation offers practical ideas to help you plan your fueling. Casper Hessellund and Mathias cover race-specific nutrition, hydration, sodium, and what can happen when your body runs low on carbohydrates.

In this episode, you’ll hear about:

- Why the balance of glucose and fructose can affect how well you tolerate higher carbohydrate intake

- What gut training involves, how long adaptation may take, and how to practice fueling regularly

- How to plan meals before a ride or race, including examples of carbohydrate-rich foods

- Why eating too much or too close to a session may leave you feeling uncomfortable

- How fueling needs differ between an easy Zone 2 ride and a race-specific workout

- How to estimate your sweat rate and think about fluid intake in different conditions

- The role of sodium and electrolytes alongside carbohydrates

- What to consider when refueling after a hard race or training session

- Why athletes may overfuel easy days and underfuel hard ones

- How ongoing underfueling can affect recovery and performance

- Why being as lean as possible is not always the best route to better performance

The conversation also explores practical ways to build a fueling plan around your training week, avoid relying on thirst as your only reminder to drink, and balance performance goals with weight management. Mathias shares why good preparation can make it easier to follow through during a ride, and why fueling well is about more than chasing marginal gains.

Whether you’re preparing for a race, training for long hours, or simply trying to make better decisions on the bike, this episode offers a useful starting point for fueling with more intention.

What if the reason your training feels flat is not your fitness, but how you fuel every hour around the ride? Former elite cyclist and nutrition founder Mathias Busk Sælgen breaks down the underfueling mistakes that keep amateur riders tired, stuck, and strangely worse after "hard" sessions.Mathias, now the owner of Noutron and a former road and gravel racer, shares what he got wrong when he was racing at 60 kilos, why eating less during the week can quietly sabotage your results, and why the biggest performance gains often come from planning, not just pushing more watts. 

If you train after work, try to "save" calories for later, or wonder why you keep bonking on longer rides, this conversation will change the way you think about carbs.You'll discover:

- Why 60 grams of carbohydrates per hour is a far smarter starting point than chasing pro-level numbers

- How muscle glycogen and liver glycogen decide whether you feel strong or empty

- The difference between glucose and fructose, and why the right ratio matters more than most riders realize

- Why 90 grams per hour is possible for some athletes, but not automatically right for you

- How heat, dehydration, and gut training change what your body can actually absorb

- Why timing your post-ride meal can matter as much as what you eat during the ride

We break down the full-picture approach to fueling: before the ride, during the ride, after the ride, and across the whole week. Mathias explains why a one-hour Zone 2 ride usually does not need carbs, why a four-hour ride after a long workday is a very different story, and how amateurs can accidentally turn a great training day into a recovery disaster by eating at the wrong time.

This is especially useful if you are a serious amateur cyclist, a gravel racer, or someone trying to balance training with work, kids, and real life. The difference between consistent progress and constant fatigue often comes down to one thing: having a plan.Perfect for riders who want more energy, better recovery, and a smarter way to fuel without copying the pros blindly.

Most people quit long before their body actually does. Volker Voit reveals what ultra-endurance really looks like when the real battle is not the bike, the watts, or the distance, it is the mind, the fuel, and the ability to keep going when everything starts to unravel.

Volker is an ultra cyclist and triathlete who did not start sports until age 32, after years of heavy smoking and drinking. Now, he is chasing record attempts across Germany and Portugal, pushing through 555-kilometer and 740-kilometer rides, night riding, sleep deprivation, cold, and the kind of discomfort that forces most athletes to stop. Casper Hessellund presses him on how far a human can really go, and Volker’s answers are as practical as they are eye-opening.

You’ll discover:

- Why ultra races are expected to go wrong, and how to adapt when nutrition, weather, or roadblocks derail the plan

- How Volker races 60 to 70 percent by mental strength, not just physical fitness

- Why he uses checkpoints and mental milestones instead of obsessing over every kilometer

- The nutrition strategy that keeps him moving for 20-plus hours, including liquid-only fueling and 120–130 grams of carbs per hour

- Why he believes most amateurs fail by chasing numbers instead of racing by feel

- The equipment upgrades that matter most, including tires and overshoes, and the gear people overpay for

- How he turned a corporate career and a late start into a life built around cycling, coaching, and content creation

Volker’s perspective is especially valuable if you are an age-group athlete, an aspiring triathlete, or someone who keeps telling yourself you are “too late” to start. He makes a powerful case that the body can do far more than most people believe, but only if you train the mind, fuel properly, and stop copying elite athletes without considering your own reality.

This conversation is a masterclass in endurance, adaptation, and perspective. If you want a smarter way to think about training, racing, and what is actually possible for ordinary athletes, this episode belongs on your list.

A surgery that nearly ended his career becomes the launchpad for an Ironman breakthrough. Lars Schmidt reveals how he went from limping through rehab and nearly selling his bike to racing his way back to the podium mindset, with a brutally practical blueprint for age-group athletes who want big results without blowing up their lives.Casper Hessellund sits down with Lars Schmidt, an ambitious age-group triathlete and coach, for a raw conversation about comeback, patience, and what it actually takes to rebuild after injury. Lars shares the full arc - from junior national-team racing and losing motivation, to military life, weight gain, a long return to sport, and finally the surgery that exposed the real problem behind years of pain: compartment syndrome.You'll discover:- Why his recovery started with just 15 minutes on the home trainer and a strict day-to-day progression- The simple rule he used to decide when to increase load: if he could do it twice, he could move up- Why he focused heavily on volume below LT1 instead of chasing hard sessions too early- How he used swimming, biking, and strength training to stay progressing while protecting his legs- Why morning pain is one of the clearest warning signs of an incoming injury- What he thinks most age-group athletes get wrong about training volume, rest days, and "recovery runs"Lars also breaks down what sustainable Ironman training really looks like for busy athletes, arguing that many competitors can get excellent results on roughly 10 to 14 hours a week if they train smart, stay consistent, and stop copying full-time pros with full-time support systems. He gets specific about session choices, the biggest wastes of training time, how to adapt when life interrupts the plan, and why family, work, and sport can coexist when you get creative.If you've ever come back from an injury, felt your fitness slipping away, or wondered whether you need insane volume to be competitive in triathlon, this episode will reset your expectations. Perfect for age-group triathletes, coaches, and anyone trying to rebuild confidence in their body while still chasing ambitious goals.Casper Hessellund is the host of Silent Effort, where he explores the mindset, methods, and hidden work behind endurance performance. Lars Schmidt is an age-group triathlete and full-time coach, known for his practical approach to training, injury comeback, and sustainable Ironman preparation.

Endurance sports are booming, but most athletes are still chasing the wrong things. Professional triathlete, coach, and endurance entrepreneur Nicholas Chase reveals why getting faster is less about doing more, and more about getting the basics right - mindset, recovery, fueling, and the courage to ignore bad advice.

Casper Hessellund pushes Nicholas on the biggest myths in modern endurance culture, from the obsession with "more" training to the influencer-fueled noise around gear, nutrition, and AI-driven marketing. Nicholas breaks down why so many athletes stall, how to spot the bullshit, and what actually separates the people who keep improving from the ones who burn out.

You'll hear Nicholas explain:

• Why endurance performance is improving, and how much of it is really better tech and better measurement
• The decision paralysis that keeps athletes stuck buying speed instead of building fitness
• Why stress plus recovery equals adaptation, and why skipping recovery leads to diminishing returns
• How to think about carbs, fuel timing, and why pro-level nutrition advice often fails everyday athletes
• The role of genetics, discipline, race frequency, community, and training with people better than you

Nicholas also opens up about the business side of endurance sports, including athlete sponsorships, brand optics, and why some companies cut the people who actually build their success. And in one of the most honest parts of the conversation, he shares the silent effort driving his own life right now - taking care of others, funding athletes, and making sure no one who depends on him gets left behind.

This is essential listening if you race, coach, train after work, or just want to get better without getting buried by misinformation. If you've ever wondered whether you need more intensity, more carbs, more gadgets, or just a better plan, this episode will reset how you think about endurance.

Lower is not always faster, and that one mistake could be costing you free speed on every flat ride. Arne Peters, the cyclist-turned-bike-builder who obsesses over aerodynamics, reveals why the smartest position is often the one riders never test.

Casper Hessellund sits down with Arne to unpack the hidden tradeoff most cyclists miss: the fastest setup is not just about shrinking your frontal area, but about finding the sweet spot between aerodynamics, power, comfort, and sustainability. Arne shares how he used an adjustable stem, hour-long road tests, and real-world power data to discover that a higher front end could actually make him faster, not slower.

You'll discover why cyclists fixate on CDA but ignore the harder question of whether they can hold the position for an hour, why some riders lose speed by chasing the lowest possible stack, and how tiny details like shoulder shrug, elbow position, helmet shape, and clothing can completely change your drag. Arne also breaks down why modern bike fits often rely more on tradition and pattern recognition than actual performance feedback.

We break down the biggest free speed opportunities for amateur and serious riders alike, including:

• why adjustable stems are one of the most underrated tools in bike fitting
• why a proper position test should come before expensive wheels
• why 30 to 32 mm tires can be faster overall for many riders
• why integrated handlebars may be more style than speed
• why aero gains only matter if you can sustain them under pressure
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If you race crits, attack in breakaways, ride solo, or just want to stop wasting watts, this episode is packed with practical ways to get faster without guessing. Arne also explains when aerodynamics start to matter most, what most cyclists get wrong about "slam stem" culture, and why the next big shift in bike fit may already be underway.

Essential listening if you want real-world speed gains, not bike-shop mythology. Start testing, start measuring, and find out where your actual speed is hiding.

Aero wins races before the first pedal stroke - and most cyclists are spending money in the wrong place. Frederik Muff, Fusion’s aero specialist and a Danish time trial record holder, breaks down what actually makes you faster, from the one change that can save real watts to the products that are mostly marketing.

Frederik has set Danish records in 10, 30, 50, and 100 km time trials, and he brings that racing experience into the wind tunnel every day. He and i get into the details that matter most for triathletes, time trialists, and serious cyclists who want speed that actually shows up on race day - not just in a product launch claim.

You'll discover why body position beats almost everything else, why the helmet-suit-position system matters more than any single part, and why a “faster” setup in the wind tunnel can still be the wrong choice in the real world. Frederik also explains when aero starts to matter, how much resistance comes from the air, why headwinds hurt so much more than tailwinds help, and why the best athletes are often the most willing to experiment.

We break down where to spend 1,000 euros for the biggest return, what not to waste money on first, and how Fusion approaches testing with elite riders like Mattias Skjelmose, Magnus Ditlev, and Sam Laidlow. Frederik shares the biggest gains he’s seen, the weirdest surprises the tunnel has revealed, and why sometimes the most valuable test result is finding out nothing needs to change.

He also pulls back the curtain on how a wind tunnel actually works, how repeatable measurements are, how aero claims get gamed, and why outdoor validation still matters. If you’ve ever wondered whether deep wheels, aero helmets, skinsuits, or lower positions really make the difference, this episode gives you the answers that matter.

Perfect for triathletes, cyclists, and endurance athletes who want to stop guessing and start making smarter aero decisions.