Why do I get so cold after a run?!
I’m sitting here working on my computer, writing programmes for clients ( googling my next pair of trainers) and I’m freezing cold. I finished a hard run just over an hour ago, showered and dried my hair. Now I’m all layered up with t-shirt and fleecy hoodie, jogging bottoms, woolly socks, hat and gloves and cuddling a hot cup of coffee. My nail beds are practically blue, my hands are like ice and my teeth may as well be chattering, I'm so cold.
This happens to me regularly. It doesn't matter if it’s summer or winter but usually after a long distance run or a training run where I've put in lots of effort. I’ll come home happy, hot and sweaty and then after an hour or so, the post run shivers set in and I'll need a hot water bottle to help warm up again.
I’ve chatted to other runners about it and had a mix of responses. Some only experience feeling hot straight after the run and can’t shower until they've stopped sweating, or they’ll come out still sweating, and others are completely mystified. Only a handful of runners know what I'm talking about so it made me question why this happens and hope that I'm normal.
It turns out it's all to do with 'Thermoregulation'. Brace yourself, here comes the science part!
The body's core temperature is set around 37 degrees Celsius and the hypothalamus in your brain helps regulate this. It does it by activating ‘heat loss prevention systems’ when we are cold such as shivering and vasoconstriction and activates heat loss assistance systems when we are hot such as sweating and vasodilation.
We all know that when we exercise our body temperature rises. This is due to heat being generated as a bi-product from a process in our body called Metabolism (this is the way energy is made to make our muscles work) and interestingly, while you exercise, 75% of the total energy created through metabolism is converted to heat while only 25% is used for muscle contraction. Goes to show that we aren’t terribly efficient with our energy production when running!
When I start running, my body begins to produce a lot of heat. This heat ends up increasing my core temperature, and my hypothalamus tells the ‘heat loss mechanisms’ to kick in. With vasodilation now working, I turn a fetching shade of pink and my skin temperature goes up so the heat is lost into the air. And if I continue to produce heat by continuing to run, I will start to sweat. Even though I'm now releasing heat, my core body temperature remains raised and is staying balanced at this new elevated temperature while I exercise.
When I stop running, my muscles stop generating heat but my core temperature is still high. So my hypothalamus tells the heat loss mechanisms to keep actively working and I continue to lose heat, as it turns out, very efficiently. My heat loss is now greater than my heat production (because I’m not running) and after time, my core temperature drops triggering the hypothalamus to change tact and boost the “I’m freezing and I need to warm up” mechanisms, like shivering, vasoconstriction (hello blue fingernails!) and the cold sensations which make you search for warmer clothes and a hot beverage.
If you are like me, a runner who suffers with the shivers after a run, being a little proactive helps reduce that uncomfortably chilly feeling. Hanging around in the cold talking to your running buddies after a run, is a sure way to induce the shivers so head indoors or somewhere warm as soon as you’re able. Change out of wet clothes quickly and have a nice hot shower or bath. Wrap up snuggly in layers of warm clothes and have a hot drink to replenish lost fluids and warm you from the inside. It’s also a great way of warming your hands!
We all have different thermostats and lose and generate different amounts of heat. It’s just one of the ways our incredible body works to keep us functioning. Learning about the ‘why’ is a great way to figure out how you can help yourself and make running even more enjoyable for you.