The oxygen-conserving potential of the diving response: A kinetic-based analysis

Area of Science:

• Human Physiology
• Exercise Physiology
• Diving Science

Background:

• The human diving response is a complex physiological adaptation to breath-holding.
• Understanding oxygen conservation mechanisms is crucial for breath-hold diving performance and safety.

Purpose of the Study:

• To compare the oxygen-conserving potential of trained breath-hold divers (BHDs) versus non-divers (NDs) during simulated dynamic breath-holding (BH).
• To investigate hemodynamic and peripheral muscle oxygenation changes during BH in both groups.

Main Methods:

• Continuous recording of heart rate (HR), stroke volume (SV), and cardiac output (CO) during simulated dynamic BH.
• Near-infrared spectroscopy (NIRS) was used to measure peripheral muscle oxygenation ([HbO2], [HHb], [tHb], TSI).
• Comparison of physiological parameters between BHDs and NDs.

Main Results:

• BHDs exhibited a distinct 'breaking point' in HR kinetics mid-BH, followed by a more pronounced HR drop, unlike the steady decrease in NDs.
• Peripheral muscle deoxygenation ([HHb] increase) was lower in BHDs than NDs at BH cessation.
• BHDs showed a greater decrease in total hemoglobin ([tHb]) in peripheral muscles, indicating more efficient oxygen redistribution.

Conclusions:

• Trained breath-hold divers demonstrate enhanced oxygen-conserving efficiency during simulated BH through coordinated cardiac and peripheral hemodynamic adjustments.
• The findings support the concept of an 'oxygen-conserving breaking point' in the human diving response, particularly evident in trained individuals.