If you’re living in Perth at the moment, you will have experienced the current joyous heatwave.  It’s not like it is unexpected – it is Perth in December, and as my husband reminded me today, Perth is by latitude the third closest Australian capital city to the Equator. We might get a regular afternoon south westerly sea breeze, but recently it has felt as if the sea must be on fire for all the comfort it provides.

I have noticed that since I started cycling (and therefore started solid cardiovascular exercise) my body temperature regulation is a lot more helpful. In winter I used to wander around the house with my pyjamas, jumper, towelling coat, slippers and socks on with a blanket tied around my waist. When I was at university I used to have an oil radiator underneath my desk and I used to quite literally wrap my legs around it in an attempt to keep warm. I distinctly remember one day at my old-old job realising that my foot felt weird, and when I took my shoe off to investigate, I saw that my toes were completely white and had lost circulation entirely. I hobbled to the bathroom, filled up a sink with gently warm water and waited for the blood to return to my toes. This is Australia in winter – it wasn’t like I was going to freeze to death.

Interestingly, I did notice that when I went to cold climates where the winter temperatures didn’t scale from a minimum of 2.C to a maximum of 18.C and back again, rather they stayed within 5 degrees of the extremes, I was fine, I could dress accordingly, and my body had no issue with the cold, but given extremes of temperature with 15.C to 20.C difference in the same day, I had difficulty dealing with the apparent cold.

In summer I was fairly OK, I would stay in the dark house and I didn’t move that much. I could deal with the heat, but not comfortably.

After I started cycling I realised that my ability to deal with temperature extremes – both summer and winter improved dramatically. In winter I no longer had problems with my circulation, I could wander around the house in a tracksuit and not want to add a beanie and gloves. In summer I found that I wasn’t nearly as lethargic in the heat as I used to be. If I had to go outside, my main concern wasn’t the heat but rather making sure that I was slathered in suncream and didn’t burn.

I’ve noticed this with running as well; which is why I guess it relates to cardiovascular fitness, today it reached 39 degrees, yesterday it was 40, but I was fine. It is as if by going outside and exercising in the heat I am telling my body “You think it’s hot? I’ll show you hot!”

What I hadn’t bet on was how much I would sweat when I run. When you cycle you produce your own wind, and you generally cool down that way. With running it is you and the still, hot air. If there is no wind, you have no wind. Yesterday before I went for my run I casually weighed myself. I don’t know why, I just did. I went out and ran 5km, and drank 400mls of fluid while I ran. When I got back, I remembered what I had weighed in previously at, and stood on the scales – books have told me numerous times that this is the easiest way to calculate your sweat loss and therefore your risk of dehydration. I’d lost 600 grams in 5 km. That is a remarkable amount of fluid to have lost in 32 minutes. You have to factor in that I decreased in weight by 600 grams, and that was while I consumed 400 grams of fluid. I drank a lot of fluid yesterday in an attempt to restore my hydration levels.

Today I had a 14km run, so with that 600 gram loss in my mind I weighed myself before I left the house to head to parkrun. When I returned I was sure that I would have lost a fair bit of weight in fluid loss, but when I got on the scale and saw the number I re-weighed myself. I had lost over 2 kilos in weight.

I have now drunk three litres of electrolyte solution, numerous cups of tea (trust me; it isn’t that good a diuretic for me, it’s completely lost its effect after the mass quantities that I consume), a yoghurt and ice smoothie and two meals and I’m still a kilo short.

I’m not a great fan of this type of weightloss, and I am having serious thoughts about my hydration strategy for the half marathon. If the weather is anything like today, I’ll probably finish it close to 4 kilos lighter than when I started. I feel this is sub-optimal.