Performance
What are CO2 tables? (Apnea training for longer holds)
By BreathTestOnline Editorial Team· Updated September 26, 2026 · Wellness guide, not medical advice
Short answer
CO2 tables are freediving apnea training: repeated breath holds with shrinking rests. They raise CO2 tolerance — the main limiter of your hold — adding 10–20 seconds in weeks.
CO2 tables are the classic freediving breath-hold training protocol. The structure is simple: a series of identical holds (for example 50% of your max) separated by rest intervals that shrink each round — 2:00, 1:45, 1:30, down to 0:45. Rising CO2 teaches your chemoreceptors to tolerate more before screaming 'breathe!'
Why they work: your urge to breathe comes mostly from rising carbon dioxide, not falling oxygen. Apnea training with CO2 tables repeatedly exposes you to that discomfort in a controlled dose, so the alarm bell rings later each week. Most beginners add 10–20 seconds to their breath test in 2–4 weeks.
A beginner CO2 table (3x per week, seated, dry only): warm up with 60 seconds of calm nasal breathing, then 8 rounds of a 30-second hold with rests starting at 2:00 and dropping 15 seconds per round. End the session there — never stack max attempts or train to dizziness.
O2 tables are the mirror image: fixed long rests with holds that grow each round. They train low-oxygen tolerance and feel easier, but CO2 tables drive faster gains for casual testers. Alternate them across the week if you train more than twice weekly.
Apnea training safety rules are non-negotiable: always dry and seated (never in water, while driving, or standing), normal air only — no hyperventilation or lung packing without a certified freediving instructor — stop at strong contractions or lightheadedness, and rest at least 48 hours between hard sessions like any muscle training.
Skip self-directed apnea training and see a clinician first if you are pregnant, have a heart or lung condition, epilepsy, or high blood pressure — and if breathlessness is new or worsening, get checked instead of training through it.
Test the theory on your own lungs
Take the instant breath testRelated questions
Performance
Does holding your breath increase lung capacity?
It trains CO₂ tolerance and control more than it grows lung size — but capacity exercises help.
Performance
How can I hold my breath longer — safely?
Sit down, relax fully, take one calm full breath — then train with short repeated holds, not extremes.
About this guide
Written by the BreathTestOnline Editorial Teamas a general wellness explainer based on widely cited breathing physiology and our own interactive timer data. Reviewed for safety September 2026. It is not medical advice, diagnosis, or treatment — breath-hold time is a fun fitness benchmark, not a measure of lung disease. If you have shortness of breath at rest, chest pain, dizziness, or a heart/lung condition, skip self-testing and see a clinician. Questions or corrections? Contact us — we read everything.