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Updated: Oct 29, 2026
Training Rats to Voluntarily Dive Underwater: Investigations of the Mammalian Diving Response
Published on: November 12, 2014
A dive into the physiological responses to O2- and CO2-tables in freedivers
Louise Declercq1, Sander Lefere2,3, Kasper Van Eetvelde1
1Department of Movement and Sports Sciences, Ghent University, Watersportlaan 2, Ghent, 9000, Belgium.
Purpose:
Current literature focuses on maximal apneas to improve apnea duration, whereas in practice, apnea training often involves two distinct forms of timed-repeated submaximal apnea protocols: "O2-tables", intended to progressively decrease oxygenation and purportedly train O2 conservation, and "CO2-tables", intended to progressively accumulate carbon dioxide (CO2) and purportedly train hypercapnia tolerance. In apnea novices, O2- and CO2-tables failed to induce strong deoxygenation and CO2 accumulation, respectively. Therefore, the aim of this study was to compare physiological responses to maximal apneas, O2- and CO2-tables in apnea trained individuals.
Methods:
After medical screening, fourteen freedivers performed three apnea protocols: maximal apneas, O2-table and CO2-table. During apnea, heart rate (HR), muscle tissue oxygenation index (mTOI) and peripheral oxygen saturation (SpO2) were measured continuously. End-tidal carbon dioxide (EtCO2) was measured before and after apneas. Capillary partial pressure of CO2 (PCO2) was measured after the fourth and final apnea. Perceived Exertion (RPE) was rated after each protocol.
Results:
RPE was lower after O2- and CO2-tables than after maximal apneas. Changes in HR and mTOI did not differ between O2- and CO2-tables. CO2-tables elicited greater increases in PCO2 and EtCO2 compared to O2-tables and maximal apneas. Maximal apneas induced greater changes in SpO2 than O2- and CO2-tables.
Conclusion:
These results suggest that, in freedivers, O2- and CO2-tables offer a less mentally and physically demanding alternative to repeated maximal apneas, allowing greater variation in apnea training while still targeting O2 conservation and CO2 tolerance, respectively.
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