Welcome to Part Nine of The Beginner’s Guide to Freediving, the best place to start your freediving journey. If you’re planning to start freediving, this chapter is about the MDR, the Mammalian Dive Reflex We’ll be examining the Mammalian Dive Reflex for freediving and how this helps us dive deeper for longer.
What Is The Mammalian Dive Reflex for freediving?
The mammalian dive reflex for freediving, or MDR, is a reflex hard wired into our genetic makeup and is brought on by immersion in water (particularly the face) and holding your breath.
It is seen in all kinds of mammals and is very strong in children. In the middle part of the twentieth century, when people started setting freediving records for the first time, the mammalian dive reflex in humans had not been recognized and it was believed that a dive to 30m would crush the lungs. Experiments on freedivers, particularly with Jacques Mayol and Bob Croft, demonstrated the extraordinary effects of the mammalian dive reflex and research is still being performed today to further investigate the incredible adaptations of the human body to breath holding.
The main characteristics of the mammalian dive reflex are bradycardia, peripheral vasoconstriction, blood shift, the spleen effect and immersion diuresis, and we’re going to look at each in turn to see the benefits and some drawbacks for freedivers.