Breath-hold training activates the dive reflex, significantly improving oxygen availability by altering spleen size and function.

The mammalian dive reflex can dramatically alter the physiology of your spleen, allowing significant increases in red blood cell count and oxygen availability to your brain and body.

The ability to dive and hold breath has led to physiological adaptations in divers, such as larger spleens and improved oxygen utilization, which may also influence their cardiovascular health.

The Bajau have larger spleens compared to nearby populations that do not dive, which likely enhances their ability to hold their breath and increases oxygen availability during dives.

The physiological sigh helps reinflate the small air sacs in the lungs, improving oxygen exchange and quickly reducing carbon dioxide levels, which relaxes the body.

Building capillary beds through long-duration efforts increases oxygen availability to muscles, which is crucial for endurance performance.

Using the physiological sigh can help reinflate the alveoli in the lungs, allowing for better oxygen exchange and immediate stress relief.

Physiological sighs can dilate the lungs and help offload carbon dioxide from the bloodstream, adjusting the ratio of carbon dioxide and oxygen effectively. Sometimes, just one physiological sigh is enough, but others may need two or three to achieve the desired calming effect.

Higher than average thyroid hormone levels in the Bajau population correlate with larger spleens and increased red blood cell production, which may enhance their diving capabilities.