If you’ve ever felt anxious, over-stimulated, or “wired but tired,” your breathing chemistry may be part of the picture—without you even knowing it.

Most people think that breathing more deeply is the key to relaxation. In reality, how much you breathe—and how well your body tolerates carbon dioxide (CO₂)—plays a major role in how calm, focused, and energized you feel. When CO₂ tolerance is low, the nervous system can remain in a subtle state of stress, even when nothing is obviously “wrong.”

CO₂ is not just a waste gas. It helps regulate how efficiently oxygen is released from the blood into your cells, supports cellular energy production, and acts as a natural calming signal for the nervous system. Because of this, healthy CO₂ tolerance also supports physical functions such as circulation, muscle relaxation, and overall metabolic efficiency—especially under stress. When breathing becomes more efficient, the body works with less effort, and many people experience reduced anxiety, clearer thinking, and a deeper sense of groundedness.

CO₂ also helps blood vessels relax and soften—one of several ways gentle, regular breath training can support overall cardiovascular balance.

In Breathe Less. Feel Better. — The CO₂ Advantage, Siv Jøssang Shields (chiropractor and breath facilitator) teaches the missing science behind breath holds, and why they are such a powerful and often misunderstood part of breathwork.