#63 - Is It OK to Exercise Before Bed?

When I first started treating people with insomnia in 2002, there was a golden rule that people shouldn’t exercise within 3 hrs of going to bed.

But as we saw with last week’s blog about whether Sleep Training raises Cortisol in Babies - we need to see what the collection of scientific studies say.

The Theory

When we are physically active, our metabolism increases. This burning of the body’s fuel creates heat and we can observe this by seeing our body temperature increase.

Indeed, the links between body temperature and sleep were a part of my PhD thesis. I saw first hand that when people went from their bed in the sleep lab - to the toilet - and then back to their bed, that it took them longer to fall asleep.

Even walking for 5 minutes can increase alertness.

Looking more broadly at our body temperature and alertness in the evening, they naturally follow the same trajectory. When the body is hotter we are more alert. When the body cools, we become sleepy.

So if we become more alert by getting up to go to the dunny (ie, Aussie slang for the ‘toilet) - surely exercising close to bed means we will become really alert and have trouble falling asleep.

Right?

The Data

Right now I could guide you through the evidence, by saying “One study found that …”. This is akin to looking at individual trees in the forest.

But I believe I have a form of ADHD so I’ll skip all that at get to the big picture (ie, the Forest).

A meta-analysis (ie, a single study that collects the data from all studies) was performed a few years ago to test whether exercising close to bedtime affects our sleep.

In all, they collected data from 66 studies. That meant they had data from a total of 2,863 people.

Here’s what they found.

Exercising within 3 hrs of going to bed:

• had no effect on the time taken to fall asleep (compared to exercising between 3 to 8 hrs before bed)

• and had no effect on the amount of sleep, but it

• helped reduce the amount of time awake during the night

So this meta-analysis showed exercising within 3 hrs before bed did not have any ill effects on sleep - and if anything - it provides the benefit of not being awake as much during the night.

Said another way, exercising 3 to 8 hrs before bed has no beneficial effect on our sleep during the night - BUT - exercising close to bedtime (within 3 hrs) does!

To me this is mind-blowing, as it defies the theory and my own observations of minimal movement (ie, going to the toilet; walking for 5 minutes) on sleep.

But it also illustrates an important point.

That as people who help others sleep better, we need to keep up with the latest research.

What I have reported here is from this study’s findings for a single bout of exercise. The study also assessed the effects of regular exercise, the type of exercise (eg, cycling), whether men benefit more than women, whether older people benefit more than young people, and whether there are different effects on sleep for aerobic vs anaerobic exercise.

If you wish to learn more, I encourage you to read pages 431-439 here.

Why am I encouraging you to read it instead of doing the work for you?

Well, not all of you will read the original research - and if you don’t, just know that it is important to find the original source of research - rather than simply trusting a Sleep Expert.

For example, I did a poll on this topic on LinkedIn, and here’s the results:

Even though the results here were very similar to the meta-analysis, I’d trust a study that analysed 2,000+ people using scientific analysis rather than 62 people completing a poll on social media.

The Good, The Bad & The Ugly

This subtitle is not meant to refer to individual people - but rather the good, the bad and the ugly that can come from within us when ‘exercising’ our social media skills.

And to stay on point with regard to updating your research knowledge and sourcing original study findings, here’s a sneak preview of next week’s important topic that I’m going to write about …

Notice anything unusual about this picture?

I saw a few (not to mention that these glasses are suppose to block those harmful blue light waves from screens … but the kids is reading a printed book).

Previously, I had seen this particular sleep expert post on social media about the harmful effects on our sleep from the blue light that is emitted from screens.

He’s not the only one.

And because I’ve invested so much time studying this phenomenon myself, I feel compelled to direct people to the original research (or at least one of my blogs that summarises this research).

However, this particular expert has not acknowledged my teachings - until this week’s post.

Maybe it’s because he has invested in a product that brings cash in for him, and thus I’ve hit a sore spot.

For me, it’s been disappointing seeing a so-called-sleep-expert spread misinformation - even when he has been previously directed toward new science.

Our conversation has seen both of us start with good intentions, which have then shown the bad side of us (my stubborness; his drifting from the science), and now they may turn ugly.

In any case, our mission at WINK is to not only bring the science of sleep to people - but also teach them about how they can use science for their own benefit.

That way they can feel reassured that letting their child cry themselves to sleep will not raise their cortisol levels (as we have heard from various mums this week).

A Thank You email sent to Dr Michal Kahn this week for her podcast educating parents about the safe, gentle and responsive aspects of sleep training (aka, graduated extinction). Note: parts of the email were blurred to protect the anonymity of the sender.

And they can also know which sources of information to trust.

And feel more confident that when they part with their money, that they’ve made the right decision to better their lives.

Like our Homepage says - Wake Up!

• Prof Michael Gradisar