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.
