Marathon running

Yeah, because often we are thinking about people at the severe end of a pathophysiology, not what the normal physiology would be if, say, we do go and run for over 26 miles.

Just on that topic, for those of us who haven't really thought about it, what does happen to your body over the course of a marathon?

Well, so you're right.

So these are people who are well on the start line, aren't they? You wouldn't start a marathon feeling significantly unwell.

But as you run a marathon, obviously, you know, you have to generate energy to propel yourself forwards.

And that is an ask of your cardiovascular system and also your respiratory system.

And the muscles are quite inefficient at generating energy.

So about 25, 30 percent of the energy that we generate to kind of sustain locomotion, sustain movement is lost as heat.

And so the body does warm up as you exercise.

I'm sure everyone knows that.

That's nothing new.

Normally, you tend to plateau.

So your thermoregulatory mechanisms, your body's ability to sweat and dissipate heat through those mechanisms is such that your core temperature plateaus, normally around 38, sometimes a bit higher, 39 degrees Celsius.

But in a small cohort of patients, your thermoregulatory mechanisms fail or aren't able to keep up.

keep pace with the amount of heat that's being generated and so you start to get hotter and hotter and that leads to the syndrome that we refer to as either exertional heat illness or exertional heat stroke those two terms are used interchangeably and that essentially is where you become unwell as a result of the hypothermia that your body's experiencing

just touching on that you've done a lot of work around that subject for the brighton marathon and looking at that exertional collapse what have you learned as a research group from your studies

the main kind of challenge we had to begin with was trying to understand what normal looked like because when you finish a marathon and you're unwell your physiology is obviously quite abnormal and you know your heart rate's high your blood pressure's potentially a bit low or even a bit high your cool temperature's high you do some biochemistry and you'll have pretty abnormal biochemistry and and it's hard to interpret that when you don't know what the normal distribution looks like So the first question we sought to answer was what a normal troponin rise is when you run a marathon.

Because we were seeing a lot of elevated troponins in unwell runners.

So we did a nice study where we looked at pre and post troponin levels in a cohort of healthy runners and compared that to runners who had collapsed at the finish line and saw that actually there wasn't a significant difference.

So there was a raise, not an unsignificant raise.

I think medium baseline was around four.

This was troponin T, high sensitivity troponin T.

And the medium rise went up to about 40, which was mirrored in the collapses as well.

So that's a normal troponin rise that we associate with exercise and obviously caveat that with these patients were asymptomatic from the perspective of having any acute coronary issue they didn't have chest pain or any other symptoms of of acute coronary syndrome we then moved on to look at renal function we know that when you run a marathon your creatinine rises and we wanted to understand that a bit better to try and understand whether or not your creatinine was rising because you were just releasing more of the precursors of creatinine so creatine phosphocreatine And therefore, we were just seeing a kind of a lag in that there was a delay in clearing it because the release was higher than usual.

But actually, what we found with that when measuring some other biomarkers of renal stress is that there is a degree of renal stress.