Why "Breathe More Oxygen" Is a Myth: Nasal Breathing, CO2 Tolerance & the Diaphragm | Zack Kramer

Most runners assume nasal breathing works because it gets you more oxygen. It doesn't — and today's guest explains what's actually going on instead. Zack Kramer, a strength and conditioning coach who rebuilt his practice around breathwork after years in CrossFit, walks through the real mechanism behind nose vs. mouth breathing: it's not oxygen uptake, it's CO2 tolerance.We cover what functional breathing actually looks like day-to-day, why mouth breathing becomes a hidden habit for so many runners, how to train your diaphragm like any other muscle, and a simple pre-run warm-up that speeds up nasal adaptation. Zack also shares his own month-long transition to full-time nasal breathing — including what didn't work.KEY TAKEAWAYS1. Nasal breathing isn't about getting more oxygen in — runners are already near-saturated (95%+). It's about CO2 tolerance, which delays the urge to breathe harder at a given pace.2. Nasal adaptation typically takes about a month of consistent practice; committing fully (24/7, including sleep) speeds it up.3. The diaphragm is a trainable muscle — a tired diaphragm pulls oxygen-rich blood away from your legs and arms before it pulls from anywhere else.4. A short CO2-buildup warm-up (exhale breath holds, ~2 minutes) can shortcut the rough first 5–10 minutes of a run.5. Chronic nasal issues (deviated septum, congestion) are common and manageable with nasal dilators — full nasal breathing isn't an all-or-nothing requirement.* Website / coaching: http://athletebreathcoaching.com* Instagram: https://www.instagram.com/athletebreathcoach/PaceBuddiesWebsite / coaching: http://pacebuddies.com* Instagram: https://www.instagram.com/pace.buddies/* Strava: @pace.buddies Chapters 00:00 Episode preview00:38 Welcome & Zack's background — football to CrossFit to breathwork03:36 Breathwork courses that shaped his approach (Oxygen Advantage, XPT)05:20 What is functional breathing?07:33 Why nasal breathing is so hard to maintain09:46 Why nasal breathing matters — filtration & nervous system14:21 CO2 tolerance introduced15:39 What CO2 actually is, and why tolerance matters18:57 Does CO2 tolerance improve performance?21:31 Adaptation period & living with chronic nasal congestion22:10 Nasal dilators — show and tell25:43 Where to start with a runner28:25 How long does nasal adaptation actually take?30:35 Running with low-intensity nasal breathing problems34:42 The oxygen myth — debunking "mouth breathing = more energy"36:04 Training your diaphragm like a muscle39:03 Why a tired diaphragm steals blood from your legs40:31 Gear demo: the Breather Fit device42:46 Gear demo: the Isocapnic device43:44 How to actually use the devices — sets, reps, progression46:18 Breath training during intervals and rest periods48:12 The pre-run warm-up that speeds up adaptation52:27 Breathing for relaxation and recovery55:09 365-degree breathing technique58:25 How to practice belly, back, and side expansion59:17 Where to find Zack & closing