What makes you, you?

When you say the word "me", you probably feel pretty clear about what that means. But what actually makes you, you in a physical sense? And why are we so different? Mike Tipton put Graihagh Jackson's stamina to the test by repeatedly exposing her to cold water to show just how different we all are...

Mike - A friend of mine who was the last remaining human physiologist, I think, at one of the universities in the North of England, and biomolecular guy asked him what he did, and he said "human physiology".  And he said "my goodness, human physiology.  How do you deal with all that variability?" and, of course, it's in the acceptance that people vary and, in trying to find out what that source of variability is that you gain understanding into why some people survive in cold or heat, why some people even survive on intensive care, and some don't.

Graihagh - This is the drive for Dr Mike Tipton's research, at the University of Portsmouth, he's finding out why we vary so much. And believe it or not, it's not to curb my curiosity when it comes to why Charlie has abs...

Mike - We share much the same genetic material, but what parts of that genetic profile are activated and which aren't is one source of the variation and the other is people's experience.  So, how much time they've spent in different condition and how physiologically and psychologically adapted to those conditions they become.

Graihagh - You've designed some sort of horrific demonstration for me to partake in today.  Can you tell me a little bit more about what we're going to be doing?

Mike - Yes. Well probably the most dangerous response to an extreme environment that we know is the 'cold shocks response' to sudden exposure to cold water because generally you lose control of your ability to breath-hold.  That leads the aspiration of just the one and a half litres that you need to drown.  And so one of the things that we've been looking at are ways of trying to protect people, not only in terms of technology (clothing, lifejackets and things like that) but also physiologically against that response.  Now we know that humans can adapt to altitude, can adapt to heat but there's always been a bit more of a question mark over whether or not they can adapt to cold, and particularly cold water.  So what we'll try and do today is see if there's a very short protocol of repeated exposures to cold that can actually improve your chances of being able to control your breathing on exposure to cold water and, therefore, diminish the chance of drowning.

Graihagh - Mike mentions drowning here because when people fall into the water, they gasp and by gasping they inhale water - it's part of the fight or flight response, you need oxygen to do either - and whilst above ground this is okay, it's a good thing, in water, it's why drowning it's the third most common form of unintentional death worldwide. Other than to stop this gasp response, the demonstration aims to show how much we all vary (my heart rate reading will be different to others for instance) but also, how adaptable we all are. This is why Mike thinks he doesn't have to do the demo with me, although it's probably not the only reason...

Mike - No, I mean there's all kinds of reasons.  Some of which you've touched upon, but there are other reasons as well. One - somebody needs to be monitoring what's going on.  And, in fact, there is a long tradition in extreme environmental medicine and physiology that the people who research in it are normally their first subjects - you know they test themselves.  And so, I've done this, which is one of the reasons you're doing it now.

Graihagh - So we're going to look at how quickly I can adapt to these cold water environments by monitoring my heart rate and, also, how long I can hold my breath?

Mike - Yes, very simple

Graihagh -   How cold is this water going to be?

Mike - I think about 15 degrees.  So that's about the average sea water temperature around about this time of the year.

Graihagh - I was a little nervous to say the least.  Once wired up to the ECG, my heart rate had rocketed to 90 beats a minute - normally it's around 50.

Mike - So what we'll ask you to do here is we'll stitch the shower on.  We'll ask you to start a breath hold just before we switch it on, and then hold your breath as long as you can.  Then, we'll also have a little look at your heart rate ECG just over that one minute, and then we'll warm you up, wait 10 or 15 minutes to get you back to normal.  Then do the same thing again and look what happens over 5 one minute immersions.

Graihagh - It's quite cold.  I feel like I could maybe hold my breath.  How long's that been?

Mike - About 30 seconds... And that's it.

Graighagh - That's it!  Like it's no big deal.  Brain freeze and slightly shaky.

Mike - You've done excellent.  So we'll keep you there and we'll put the water to warm and that will warm you through.  Then you can come out and have a bit of a rest and we'll go again. Shall we put that straight round to warm?

Graihagh - Yes. [screams] That's not warm!

Mike - I timed your - depends where you want to mark the end of your breath hold - but if it's with the start of speaking, it was about 2 seconds.

Graihagh - Yes.  Well the initial shock I think I did one of those pwhh - sort of horsey noises.

Mike - Actually, do you know what you said (bleep).

Graihagh - Can't use that in the recording.

Mike - But actually, that's really common

Graihagh - Assured me that I was really normal in my poor language choices.  I did four more of those minute long immersion. Later, over a hot cup of coffee, Mike talked me through the results...

Mike - So what we've got is the ECG which was recording your heart, and we've got a respiratory trace as well so we can get the breath hold time.  If we look at the first one, of course, what we can see is that, unsurprisingly, you were quite excited about the prospect...

Graihagh - I'd go for nervous, not excited. 

Mike - Yes.  Well your heart rate was quite raised.  You managed a breath hold time of about two seconds on your first one, and we can see exactly where that finished here because there's quite a lot of movement on the ECG trace that equates the expletive that you offered us at that time, but anyway it's interesting.  So there's a big respiratory drive that's come from going under the cold shower that's prevented you from holding your breath. Interestingly, on the second one your heart rate was higher.  Of course, once you've done it once, you're just that little bit more anxious the second time and the response is greater.  So going through three, four, and five, your breath hold times went from sixteen on number three, to 44 seconds on number four, and 45 seconds on number 5.  Which suggest to me, that you'd almost reached the level at which you were not going to habituate any more.  Your heart rate response kind of supports that.  It tends to follow a different pattern in that it stays high and then suddenly drops.  So you were 125 on the first, 150 on the second, 65, 62, 56.  Now that, I mean 56 is a remarkably low heart rate so, congratulations on that but it does also tell us that you've probably habituated as much as you're going to do.  So that five immersions was enough to reduce that response.

Graihagh - What's going on for me to adapt to that environment, in my body?

Mike - Well we think the adaptation occurs somewhere central to the peripheral cold receptors. Because we see a difference in the profile of the heart rate habituation and the respiratory habituation, it's probably happening beyond that point as well.  The other think that kind of suggests that is that, if we do a full habituation to cold, we can reduce the cold shock response by about 50%.  We then ask people to come back 14 months later and it's still reduced by 25%.  So it's a fairly permanent alteration in the neurophysiological response to a peripheral cold response stimulus.

Graihagh - Because, interestingly enough, I felt much, much better by the fourth and fifth one.  It wasn't as uncomfortable and I felt much more relaxed actually.  So surely, psychology has something to, some role to play in this?

Mike - It definitely does.  In fact, when we look at the two variables we examined today - heart rate and ability to breath hold.  Well heart rate is, in normal circumstances, is not under very much conscious control but, of course, breath holding is.  You've got a drive coming from those skin receptors which you're trying to suppress, and so part of what's going on is you're getting better at suppressing that drive as well as the drive going down as well.  We know that there is a sort of psychophysiological component.  But also, you can sensitise people; they get a little but anxious.  So there is a well-known presenter who has come and been immersed with us, and I always start an immersion in cold water by counting down 5, as I did today and now, if I see this person on the street I only have to count down from 5 and I think is heart rate doubles.  So we've kind of sensitised him.  And so yes, absolutely, this is not just a physiological adaptation, it's an interwoven physiological and psychological adaptation. So, if we put this in the greater context, the ability for that adaptation is a combination of your genetic profile which determines other things like fitness, fatness, and also your experience of exposure to the environment. So everybody has the ability to adapt.  That adaptation is limited compared to what we can do intellectually and is also determined by a combination of the environmental exposure that you've had and the genetic basis of you as an individual.