Human Limits

Exploring performance and health with Michael J. Joyner, M.D.

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A Deep Dive & Risk

Last weekend there was a “60 Minutes” segment on the emerging sport of free diving.  That plus the death of free diver Nicholas Mevoli got me thinking about risk and extreme sports.  When things like this happen sometimes I get calls from the press and almost always my physician colleagues want to know “why anyone would try these things?”  Here are the ideas I cover in response to that question.


The Power of a Subculture

People who attempt to set extreme records or push themselves to the limit are usually part of an extreme and somewhat closed subculture.   Their friends and peer group share an intense interest in an activity and it becomes literally what they eat, breath and dream about.   A question like “how are you today?” from a casual friend or co-worker is frequently answered with something like “pretty good, I did a hard 15 mile run first thing this morning, we will see how the 10 miler this afternoon goes.”  This might be seen as an odd response in the real world, but totally normal in an extreme athletic subculture.


That sort of dialogue is an example from running but similar discussions can be had with those who are really committed to just about anything.   If you have never been part of an extreme athletic subculture three books that describe them in detail are “Muscle”, “Once a Runner”, and the recent the “Secret Race” by Tour de France rider Tyler Hamilton.  So, there is plenty of social reinforcement to “go for it” from the subcultures that people who are committed live in.


My Neurotransmitters Made Me Do It

One of the hallmarks of traditional addiction is the need to use ever more external stimulus to get the same satisfaction from whatever you are addicted too.   Traditional addiction to drugs rewires brain circuitry and neurochemistry to make this happen and there is evidence that gambling can do the same thing to susceptible individuals.  For many a peak and intense athletic experience is sometimes followed by a letdown as the excitement associated with the planning, training, and anticipation of the big event vanish afterward.   The obvious solution to this problem is to find an incremental challenge and start the whole process again.   Parallels with gambling seem appropriate here and when you mix what is happening in the brain with the right subculture it is pretty easy to see how the need to do ever more extreme things happens.


The Environment

A lot of disasters and deaths occur in extreme environments.   Think altitude, diving, hot and cold.  There are tremendous physiological adaptations that can be activated both acutely and in response to training that help us do more or go longer in extreme environments, but when things fail they can fail catastrophically.   There is a quote about bankruptcy from the “Sun Also Rises” by Earnest Hemingway that applies to physiological responses to extreme challenges:


“How did you go bankrupt?  Two ways. Gradually, then suddenly.”


A classic example of this is watching soldiers faint while at attention on a hot day or seeing a patient respond to potentially life threatening blood loss.  If you were to measure the vital signs they would be pretty normal until just before loss of consciousness when there is a sudden drop in blood pressure.  When this happens many of the physiological systems that are compensating for the challenges of not enough blood returning to the heart fail essentially at the same time.  You can tell a similar story about catastrophic physiological failure in response to other severe stresses as well.   So, people feel OK until they don’t and in extreme environments the distance between OK and death is not that far.


You Are On Your Own

Of the people injured in the Boston Marathon bombing essentially everyone who made it to the hospital alive survived.   This is one of the main lessons from military combat casualty care for civilian medicine.  Extreme sports take place in extreme environments distant from the types of comprehensive medical care that make an incredible array of injuries and illnesses survivable especially in young otherwise healthy patients.   Other things that come to mind are the availability (or lack thereof) of specific equipment and logistical support needed to do challenging things in a safer way.   Getting a lot of hardware and a support crew to a remote location is challenging and sometimes there might be a temptation to try to do more with less.


Risk Amplifies

Extreme environments, the limits of physiology, and logistical issues are all risks but they are all amplified by poor judgment.  I like to tell people that taking four 3% risks at the same time doesn’t mean you have a 12% risk of failure.  Instead the risk is more like 3x3x3x3 or 81%.   This is a theoretical example but things really do seem to multiply while doing extreme things in extreme environments.  Time and time again you hear about people choosing to push it just a bit more prior to a disaster.


I Am All For It

Based on the observations above you might think I oppose people taking on extreme challenges in fact I am all for it.  Back in 2011 when Diana Niad was attempting to swim from Cuba to Florida I commented to PBS that questions about “why” do it


“miss the point, at some level, you’ve got to admire anybody who wants to test the limits of human potential in general, and her own limits, in specific…It’s a good thing we’re not all average.”


That having been said, I just want people to understand what they are getting into and avoid getting sucked up by their subculture and neurochemistry into challenges they are not prepared for in truly unforgiving environments.

One Response to “A Deep Dive & Risk”

  1. December 5th, 2013 at 6:49 pm

    Bill Hagan says:


    I really enjoy your blog posts. Your data-driven approach to questions is a refreshing change to the ideology-driven approach that seems to dominate our world these days.

    I wanted to comment on your post regarding deep diving and risk taking in general. I agree with your basic conclusion that when we engage in activities that involve multiple risks (ways to fail), the probability of failure is likely to be much larger than one might intuitively estimate. But I suggest that the reason for this has to do with our inability to accurately estimate the probability of failure for some risks rather than the mathematics of probability.

    First, a bit about calculating probabilities: In your example you say “I like to tell people that taking four 3% risks at the same time doesn’t mean you have a 12% risk of failure. Instead the risk is more like 3x3x3x3 or 81%.” However, the mathematics is a little more complicated. The probability of failing is 1 minus the probability of not failing at any of the four risks, or 1 – (1-p1)(1-p2)(1-p3)(1-p4), where the probability of failing at each is p1, p2, etc. For your example, the overall probability of failing would be 1 – (1-.03)^4 = 11.5%. You are right to say that it is not 4 x 3% = 12%. It is actually slightly lower! However, if the individual failure probabilities are small, it can be shown mathematically that just adding them up is not a bad approximation.

    If you have underestimated just one of the failure probabilities, then the overall probability of failure can rise dramatically. For example, suppose that three of the four risks had a failure probability of 3% but the other one had a real failure probability of 50%. Then the overall probability of failure would really be
    1 – (1-.50)(1-.03)^3 = 54.4%, much higher than the 11.5% calculated above. If you have seriously underestimated all four risks, then the overall failure probability can really take off. For example, suppose the probability of failure of all four risks is not 3% but is really 34%. Then the overall failure probability is 1 – (1-.34)^4 = 81%! (I chose 34% to get to your 81% example.)

    Now for my conjecture: I speculate that the reason things go wrong more often than one might think is that if you engage in, say, four risky things at the same time, there is a good chance that you have underestimated the probability of failure for at least one, if not more. After all, the probability of failure is usually just a guess or estimate and we are not good at identifying all the ways that something can go wrong (remember the Martian lander that crashed because some of the designers used metric units and some used English units? I’ll bet that possibility was not in the risk analysis!). As we showed above, seriously underestimating the probability of failure of only one risk can lead to a dramatically higher overall probability of failure and possibly disastrous results.

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