What determines how long a person can hold their breath?

The main factors are arterial O2 stores (lung capacity × SpO2), myoglobin-bound O2 in muscles, resting metabolic rate, spleen contraction (trained divers), and CO2 tolerance. Elite freedivers store approximately 2.5× more oxygen than untrained individuals.

At what SpO2 does shallow water blackout occur?

Loss of consciousness typically occurs below 50–55% SpO2 on ascent when the partial pressure of oxygen drops as depth decreases. This is why hyperventilation before a breath-hold dive is extremely dangerous and should never be practised.

Free Diving Breath-Hold Time Predictor

Predict maximum static breath-hold time from lung capacity, resting heart rate, and oxygen consumption metrics. Identify the diaphragmatic contraction threshold and safe limits.

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Frequently Asked Questions

What determines how long a person can hold their breath?

At what SpO2 does shallow water blackout occur?