Hazards of hot weather running

Sunday was the hottest day of the year so far here in London. It was also very humid and muggy. But a long run was on the schedule. I tried to go early, but in the end it was 8 o’clock before I stepped out of the door, so it was already getting warm. I know that compared to some parts of the world 28 degrees centigrade is not that hot, but for me hot sunny weather is really not conducive to a 2 hour run. A couple of things make hot weather running a bit of a pain.

First reason: I have vitiligo – a skin condition that means that I don’t have pigment in much of my skin. It’s an autoimmune condition, and doesn’t cause me any problems – except that I cannot tan, and my skin burns in 5 minutes of sun exposure. I can’t run in long sleeves and ankle length running tights in the hot weather so Factor 50 sun cream is essential. I always wear a hat too, for extra protection for my face. Also I get really bad headaches if I don’t wear a hat. I manage ok if I’m careful!

Second reason: My hands tend to swell up in the hot weather. On Sunday this seemed to be particularly bad. My fingers were really uncomfortable. Why does it happen? And is there anything that can be done to prevent/lessen it?

It is a normal part of physiology. When running the blood flows to those parts of the body that are working hard – heart, lungs, muscles. But not the arms and hands. However the blood vessels in the hands react to this reduction in blood flow by opening more. This response is exaggerated in hot weather as the body tries to cool down. Fluid leaks into the tissues and causes swelling. The lymph system will eventually clear this excess fluid, but when running this action is slowed because the body is busy dealing with other things. Fluid also tends to pool at extremities due to gravity – so walking with your arms by your sides may lead to swelling. (And that’s a reason why your feet can swell too – and why running shoes should be a bit bigger than your normal size.) Once the body returns to a resting state the fluid will be reabsorbed quite quickly – within a couple of hours. That is exactly what happened to my fingers – by lunch time my fingers were back to their usual bony state!

Rarely, swollen fingers can be a sign of something much more serious – hyponatraemia. This is when sodium levels in the blood drop dangerously and as a consequence water passes into cells causing them to swell. It also affects the blood-brain barrier – increased permeability can cause the tissues around the brain to swell. This leads to neurological symptoms such as confusion, dizziness and nausea. Hyponatraemia is caused by drinking too much water while exercising. It affects long distance runners (and cyclists etc). The advice is to drink when you feel thirsty, rather than on a timetable. I don’t think this was my problem on Sunday as although I felt very tired, I wasn’t confused or dizzy.

What can I do about the swollen fingers problem? Suggestions I have read include raising arms above the head or turning them in circles; clenching and unclenching your fists; stretching out your fingers. Personally I don’t think those ideas are very practical on a run, but I do try to do some of them sometimes! I do drink water – when I feel thirsty. I also have some isotonic dissolvable tablets which I sometimes use. My plan is to always have some of this on a long hot run in the future, as well as plain water. Carrying a hydration pack makes this a bit more feasible. I can have water in the pack, plus a 500ml bottle of isotonic solution.

Anyway – today the weather is back to English summer normal – i.e. raining. No problem!

Throwback to 2017 – a very hot 10k in Richmond Park with my friend Leah. We both came first in our age categories! I think there was only me in my age category though 😀

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