Exercise-induced insomnia

It’s 1am and I’m wide awake.

I feel completely exhausted after the weekend’s exertion, but for some reason my body  won’t allow me to sleep. Yesterday I did a recce of leg 3 of the Bob Graham Round, a total of 17 miles with 2300m of elevation gain. I followed this up today with legs 4 and 5, covering 23 miles and 2900m of elevation. I then hitched a ride out of Keswick as swiftly as possible (nice weather at the weekend seems to encourage pottering about the quaint towns of the Lake District on a tremendous scale), and got the train home to Edinburgh. I was back in good time, so had a civilised dinner with Sofie, and was in bed before 10.30pm. I felt totally spent (in a good way!), and my body was evidently crying out for some solid rest.

But I couldn’t sleep.

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Feeling good on my recce of leg 3 of ‘the Bob’

 

Not the first time

After every marathon or ultra marathon I’ve ever done, the same thing has happened: I’ve arrived home totally whupped, felt like I could sleep for days, but have then woken during the night, and then been wide awake come 4 or 5am.

What’s the deal? How can I be so tired and my mind be crying out for one thing, but my body just won’t play ball?

Hormones

It appears I’m not the only one that has suffered this same phenomenon. There seem to be a number of factors that can influence our post-exercise sleep, such as the amount of caffeine we consume when training (think of the high caffeine gels people routinely knock back every hour when exercising), dehydration, and an elevated core body temperature, but for me the most compelling one is the effect that exhaustive exercise has on our hormone levels.

Exercise excites both our nervous and endocrine (consists of the glands in our bodies that produce hormones) systems. The longer, more strenuous the exercise, the more we excite both of these systems. There are two hormones that seem to play a large role in disturbing our sleep: cortisol and norepinephrine. Adrenaline is another hormone that’s elevated during sustained exercise, but it falls back to normal levels quickly after finishing. Unfortunately the same cannot be said for cortisol and norepinephrine.

Cortisol is a steroid hormone, and plays an important role in our metabolism of glucose, which ensures that our muscles have the fuel they need to keep going. It is produced in response to stress, and our bodies normally self-regulate its production, with levels at their highest immediately after waking up, then falling in cycles as the day continues, being at their lowest when we go to bed. This is handy, since another effect of cortisol is that it blocks the production of melatonin, the sleep hormone. So, normally when we go to bed, our cortisol levels and low and melatonin high, and we fall asleep. When we do exhaustive exercise (what is meant by ‘exhaustive’ is of course highly personal, but for me seems to be running fairly hard for 3 or more hours), we elevate our cortisol levels, which then fail to return to that nice low before going to bed, causing us to remain awake even though our bodies are crying out for sleep.

Norepinephrine is released into the blood stream when the body is stressed, and can raise our heart rate, trigger the release of glucose (sugar) into the blood stream, and increase the blood flow to our muscles. These are all brilliant, essential functions when we’re out doing the activity; much less so when we’re trying to get some kip. A recent study showed that norepinephrine levels can remain elevated for up to 48 hours after exhaustive exercise.

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Sunrise over the Scafell range, seen from Yewbarrow. Worth the subsequent insomnia.

The solution?

It’d be easy to simply suggest not exercising as much, thereby not stressing our bodies out as much, and not elevating our hormone levels to the same extent. The reality is that simply isn’t an option if you’re hooked on long-distance running, ultra-endurance events or any other activity which involves sustained physical exertion for a long period.

Given this, I’ve found yoga, stretching and deep breathing/ meditation to help somewhat to unwinding after a big physical exertion. Cold showers/ baths and icing seem to help too.

But at the end of the day, it seems that insomnia in one form or another is unfortunately an inevitable side effect of exercising lots. I’d say it’s a price worth paying.