Diary Of A Road Runner

5k Tempo Run - Warm and Humid - 25m 17s

I’d had a couple of rest days after my longer run on Sunday, and was feeling fresh and ready for a run - I had one of my 5k specials planned, mixture of a tempo run and unofficial time trial! Judging from my run on Sunday, it seems that I can manage 26 minutes pace for 5k comfortably, and can likely maintain it over a full 10k, so I wanted to run a bit faster than that (using the “hard, pushing towards uncomfortable, but not flat out” definition of a tempo run), and was hoping to run sub 25 for the second time.

This didn’t work out - weatherwise, it felt a bit warm and muggy before I set off, so humidity must have been up (when I checked later it was relative humidity of 75%). I set off at a slowish pace and got to 2k, and even at that point I was wondering if I would have to stop, as I wasn’t feeling all that great and my legs felt a bit heavy, although I was managing to keep at roundabouts 5 mins per k pace, but had to slow a bit to keep myself from blowing up, as I at least wanted to finish my paltry 5k! I just felt if I went any quicker, I would over do it and not be able to finish, and there’s something within me that doesn’t like admitting defeat by stopping before I’ve done what I set out to do!

As it happened, I was able to go a little bit quicker at the end, but it wasn’t like the sprint finish I managed when I first broke the 25 minutes barrier. I was very glad to stop in the end and didn’t have much at all left! I felt really warm, and was still gasping for breath 2-3 minutes after stopping, plus my legs felt wobbly. And I had practically killed myself to run 5k in 25m 17s! I have run it faster the last 2 times!

However, I did a bit of research, and there are theories about how conditions affect runners. So, how does humidity affect runners and their running? In my case it seemed to reduce my efficiency, I was having to work much harder and I could actually sense my heart and lungs working overtime, plus recovery time after the run seemed to take a lot longer.

One thing humidity does is stop the body cooling as effectively - in dry air conditions, the sweat evaporates quickly and cools the skin, helping the body to cool down. The higher the humidity, the less effective this system becomes, so the body can’t cool down normally.

An interesting theory I read claims that because their are more microscopic water droplets in the air when it’s humid, it means that your oxygen supply is effectively saturated with water - although there is plenty of excess oxygen in the air, the amount of water droplets reduces how much and how effectively the lungs can process it - so the heart and lungs start working harder because they are doing what is normally expected of them, without getting sufficient oxygen. Some say this theory holds no water (if you pardon the joke!) but I definitely suffered from this today - my lungs were screaming for oxygen by the end, and it was unusual for me to take quite so long for my breathing to get back to normal - as if the lungs were working a few more minutes to get all that oxygen into the starved heart and muscles?

It’s interesting - I will definitely keep more of an eye on the conditions in future, and it may be an idea to slow my pace on muggy humid days - hopefully it will have almost been like a bit of altitude training, and next time I run in OK conditions, I will smash through my target time!