Modified ventilatory response characteristics to exercise in breath-hold divers

Area of Science:

• Physiology
• Exercise Physiology
• Diving Medicine

Background:

• Elite breath-hold divers (BHDs) are known to have blunted ventilatory chemosensitivity to carbon dioxide (CO2) at rest.
• Adaptations in ventilatory response to dynamic exercise in BHDs remain poorly understood.
• Understanding these adaptations is crucial for assessing physiological limits and potential risks.

Purpose of the Study:

• To investigate the ventilatory and metabolic responses to graded cycle exercise in elite BHDs.
• To compare these responses with those of scuba divers (SCDs) and healthy controls.
• To determine if BHDs exhibit unique adaptations in chemosensitivity and breathing patterns during exercise.

Main Methods:

• Eight elite BHDs, 8 SCDs, and 8 controls performed graded cycle ergometry.
• Measurements included ventilatory parameters, end-tidal partial pressure of carbon dioxide (petCO2), and blood lactate.
• Analysis focused on lactate threshold (θL), respiratory compensation point (RCP), and maximal exercise capacity.

Main Results:

• Maximal power output was similar across groups.
• BHDs demonstrated a lower θL and RCP relative to VO2, with higher petCO2 and estimated arterial pCO2 (paCO2) at these points and exhaustion.
• BHDs exhibited a significantly slower breathing frequency for a given tidal volume during exercise.

Conclusions:

• Elite BHDs display a metabolic shift towards anaerobic energy production during exercise.
• Reduced chemosensitivity to CO2 during exercise and a distinct ventilatory pattern characterize BHDs.
• These findings highlight unique physiological adaptations in elite BHDs during dynamic exercise.