I recently wrote a post where I mentioned that blackouts “don’t cause brain damage,” and after some discussion I realize that I have been simplifying a very complicated topic regarding freediving and the associated physiology and research. In response to this I wanted to take a closer look at the results of blackout and the possibility of brain damage.
So to be completely honest, there’s no concrete way to say for sure that blackout does not cause some level of brain damage. We just don’t have enough research to be 100% certain. All we can do for now is look at the studies that are available and come to our own decisions about the risk.
What I think:
Based on my knowledge and experience I believe that blacking out does not cause significant brain damage. I would argue that many other activities in which people engage, including athletic (i.e. football) and recreational (i.e. drinking) activities, have a much greater risk of brain damage than hypoxia resulting in blackout.
So let’s look at what would bring me to such a conclusion.
Freediving guru and coach, Kirk Krack of Performance Freediving International says that he generally tries to dispel the myth that brain damage occurs within the first four to six minutes of breath-holding.
“During breath-holding that may pass this four- to six-minute time-frame, a pulse and blood pressure still provides oxygen to the brain even though the body is going through a varying degree of hypoxia,” he said.
While a diver’s body becomes gradually more and more hypoxic (lower than normal levels of oxygen) during a breath-hold, they’re not actually without oxygen (anoxic) during a conscious breath-hold.
Even at the moment of blackout a diver’s body still has a reasonable amount of oxygen. It’s only once blackout occurs and has sustained for a while that the diver risks reaching anoxia, where the real risk of brain damage begins to occur. Anytime a proper freediving safety system is employed a blacked out diver should not remain unconscious/non-breathing for long enough to reach anoxia.
While there are comparatively few studies of freediving as compared to activities like scuba diving, there are a few that have directly targeted the issue of brain damage, including the one outlined below.
*In 2002 at the Kona World Cup in Kona, Hawaii, Dr. Lynne Ridgeway conducted neurological exams of divers within five minutes of surfacing following deep, competitive dives. This study was conducted on 92 freediving participants. These people had varying degrees of success in their dives, some experiencing losses of motor control and blackouts. They were administered an exam on the boat immediately after diving and the study conclusion was that no neurological impairment was detectable.
I don’t want to say that we’re making conclusions from the limited resources we have available to us, but I would say it’s reasonable to move forward by saying that freediving blackout, handled properly, has little risk of causing significant, easily measurable brain damage.
I personally feel confident enough in this statement to continue to pursue my goals in the sport. However, it’s important that all freedivers to make that decision for themselves. In a growing sport where research is limited we all have to be responsible for accepting the risks.
As I find more information on this topic I’ll post it here to keep you all updated, but feel free to post links to other studies, etc. in the comments section.
*Thanks to Performance Freediving International for providing information on this study.