Diving response after a one-week diet and overnight fasting.

Area of Science:

• Physiology
• Sports Science
• Diving Medicine

Background:

• Investigating the impact of overnight fasting on physiological responses during breath-hold diving.
• Hypothesizing that fasting optimizes diaphragm excursion, blood shift, and metabolism for improved diving.
• Exploring the potential of fasting to enhance the diving response without compromising athlete safety.

Purpose of the Study:

• To evaluate the effects of overnight fasting versus a post-breakfast state on breath-hold diving performance.
• To assess physiological parameters including apnea duration, cardiac output, and blood markers.
• To determine if fasting optimizes the diving response at a depth of 30 meters.

Main Methods:

• Eight divers completed two 30-meter dives: one after breakfast, another after overnight fasting.
• Apnea phases (descent, static, ascent) durations were recorded.
• Impedance cardiography measured trans-thoracic fluid index (TFI), stroke volume (SV), heart rate (HR), and cardiac output (CO); blood pressure, O2 saturation (SaO2), glucose, and lactate were also monitored.

Main Results:

• Overnight fasting significantly increased the static apnea phase duration compared to the post-breakfast condition (37.8s vs. 27.3s).
• Fasting led to a lower mean stroke volume variation and cardiac output during the static phase.
• Post-dive, divers in the fasting group exhibited higher SaO2 (92.0% vs. 89.4%) and lower blood lactate levels (4.2 mmol/L vs. 5.3 mmol/L).

Conclusions:

• Overnight fasting enhances breath-hold diving performance, evidenced by longer static apnea and improved physiological recovery.
• Achieving an optimal metabolic and splanchnic state through fasting positively influences the diving response.
• Fasting appears to be a safe strategy for improving dive performance at 30 meters.