Running in Summer, too hot to handle?

Hyperthermia in Fellrunning

Sitting in a stream splashing yesterday, I had a nagging feeling there was something I should have done.  I splashed my head and neck and filled my water bottle and drank deeply.  For the past 3 hours I’d been running over the hills of the Peak District.  It had been a still, sunny and humid day.  I’d drunk all the water I’d carried and topped up from occasional spring but as I ran off the hill I was a little light headed and very thirsty.   I was feeling the first effects of heat exhaustion.

And that was what I should have done.  Incidents at a number of recent races have highlighted the problems of Hyperthermia (getting too hot – as opposed to Hypothermia which is getting too cold).  I had promised a piece on the subject for the Fellrunner.

The dangers of being too cold on the hill are, I hope, now well known.  What may surprise however is that the dangers of a runner getting too hot can, potentially, be much more serious.

The human body is marvellous.  When we get cold it shivers to generate heat,  When we get hot different coping mechanisms get rid of excess body heat; sweating, breathing harder and increased blood flow to the surface of the skin.  In normal circumstances these mechanisms work well.

Racing up a hill, at speed, on a warm day isn’t however what most bodies would consider normal and the core temperature can increase to a dangerous level quite easily.

As humans we operate most effectively with a body temperature of around 37C.  Hypothermia kicks in when this drops with a risk of death if the drop is 7 or more degrees.  Conversely an increase of only 4C is needed for Hyperthermia to present the same risk.

Hyperthermia is more likely to happen on hot windless days, especially in a humid environment.

So, what’s actually happening in the body whilst running?

During exercise, blood pressure rises to deliver more oxygen to working tissues, body temperature increases, as does the amount of work required to maintain a stable temperature.   As more and more moisture and electrolytes are lost from the body, this lowers blood pressure and limits the ability to sweat.

Effectively Hyperthermia is the body over heating to a point where it is unable cool itself down.

There are 2 types of Hyperthermia; Heat Exhaustion and Heat Stroke

Both are dangerous with Heat Stroke being the more dangerous and it’s important we can recognise the different symptoms.

Signs and Symptoms and Treatment












Prevention and Preparation

Preventing heat exhaustion and heatstroke is certainly much more preferable than treating it.

  • Drink plenty of cold drinks, carry an extra bottle for the long race especially if there is no water on route.
  • wear light-coloured, loose clothing
  • use streams and other water sources to douse water over skin and clothes
  • whilst training, avoid running in the middle part of the day between 11am and 3pm when the sun is at its strongest
  • avoid excess alcohol
  • pace yourself in a race, much better to set off slowly

It can take experience and a brave decision not to continue if you start getting too hot and very thirsty, but it’s worth considering the consequences if you don’t make that decision.  If you have to ask whether to push on the answer is probably ‘no’.  There is always next year.

Many thanks to the doctors and medics of Woodhead Mountain Rescue Team for their input in verifying the technical details.

Thanks also to Brian from Chorlton for his honesty and agreeing to let us publish his account of heat exhaustion earlier this year.  Brian exhibited some classic heat exhaustion symptoms; pale skin, cramping, dizziness and vomiting.  As he says at the end, it’s better to retire than push through and end up in hospital.  Worth noting are the other runners who gave up their race to attend other runners in distress.  They are to be commended and I hope we would all do the same in a similar situation.

Runners Tale

Brian Barnes – Chorlton Runners Black Sheep.

On the 29th June 2019, along with 26 other Chorlton Runners, I attended the Whaley Waltz fell race. The race was one of our championship races and had a good turnout.

I am an experienced fell runner with many Ultras and AM/ALs under my belt so thought this race a relatively easy afternoon out.

It was a hot day, as forecast, and we had posted up a warning before the race to our members about hydrating and wearing hats etc.  I was well hydrated.

It turned out to be the hottest day of the year with 34 degrees being recorded in London.  Whaley Bridge reached 29/30 degrees.

We were out in the sun quite a bit at the start as we had to register and then wait for the carnival to go past.  It was 13.30 or so before we started.  This meant we were running at the hottest part of the day.

I was determined to do well.  I set off steady and pushed myself more than usual.  This was to prove counter productive for my club points total.

The water stops were great, posted at stiles where we were delayed anyway, taking away the pressure of deciding to press on and not rehydrate.

It was scorching, even on top where you would normally get some moorland breeze.

I was doing really well or so I thought, on the heel of one of my team mates who is normally much further ahead.

We only had 1/2 a mile or so to go.  I was nearly home with the river crossing to negotiate, at least it will be cooling.

Then the wheels fell off!

I started throwing up, saw some shade and just headed for it on auto pilot.  My legs went and after that things got a bit hazy.

A team mate came over very soon after I collapsed but I only have a vague recollection of him; he told me about it afterwards.

“You were sitting down but very out of it and looking very grey.  I spoke to you and asked you if you were ok but you didn’t respond.  There were 2 marshals with you and I told them your name and that I was a team mate.  They said they had contacted colleagues and an ambulance was on its way.”

A very nice runner from Goyt Valley Striders called Louise came over to help me and she stayed with me for ages, taking my pulse and only completing the race when she knew I was ok.

I was told an ambulance had been called, by this time more team mates had joined me.  I was coming round slowly but my hands were tingling and cramping and I still didn’t feel I could stand.

After what seemed an age the ambulance drivers came along and introduced themselves as Devon and Dale.  I still had my sense of humour as I thought “Devon and Dale“ at a fell race, you couldn’t make it up!   They asked me If I had lost consciousness, I didn’t think I had.

After an initial try to fix ECG equipment to me they gave up as I was too sweaty.

Team mates supported me in walking to the ambulance where a welcome long blast of aircon was administered with more water and a full ECG.

They gave me the option of going to hospital but team mates said they would drive me home and even drive my car back too.  I wasn’t with it enough to drive, still feeling unsteady and a bit “out of it”.  I believe I had heat exhaustion, the precursor to heat stroke.

I had hydrated, put on suncream, wore a hat and stopped at the water stations to drink and poured some over myself.   If I had been as cautious as usual I would have finished and instead of a DNF I would have had points in the bag.

Others faired worse than myself.  A team mate helped a young lad and I was told he went to hospital needing intravenous fluids.

So the moral of the story, although it is a race, keep it steady in those conditions.  As a team mate said, better to DNF the race than to DNF the day!