The Bohr effect, in one sentence
Haemoglobin releases oxygen to tissues only in the presence of CO₂ — so chronically low CO₂ from over-breathing actually reduces how much oxygen reaches your cells.
Why mouth breathers over-breathe
Mouth breathing tends to be larger and faster than nasal breathing. Over time, this lowers CO₂ tolerance, so the body needs less stimulus to feel breathless, and energy drops.
The one-week fix
Day 1–3: tongue on palate, mouth closed, all day. Day 4–7: add three 5-minute sessions of 5-5 coherent breathing. Most people notice the 3 PM dip ease by day 5.
Measuring change
Take a control pause on day 1 and day 7 (see our control pause article). Most people gain 3–8 seconds in a week.
Log your sessions in Breathe On and explore the matching guidance at [/breathing-for/fatigue](/breathing-for/fatigue).