Episode 380: Breathing, CO2 Regulation, and Performance: Deep Dive with Respiratory & Sleep Scientist Martin McPhilimey

In this episode, I sit down with respiratory and sleep scientist Martin McPhilimey to do a deep dive into breathing, CO₂ regulation, and how it actually impacts performance, stress, and sleep. We get into why respiratory physiology is way more complex than most people think, how his clinical and research background shaped his approach, and why breathwork exploded during COVID with names like Wim Hof and James Nestor. From there, we dig into allostatic load and why piling on high-stress practices—like aggressive hyperventilation or cold exposure—can backfire if you’re already running hot. We also talk about the difference between actually relaxing your system versus just dissociating from it. We cover how inspiratory muscle training can improve performance and recovery, why respiratory rate is one of the most sensitive markers of stress, and question some common ideas like “CO₂ tolerance.” We also touch on the risks and limited data around inhaled CO₂ therapies and what actually makes sense to apply in the real world.