Sleep or Exercise? 3 Reasons Why You Shouldn’t Work Out When You’re Lacking ZZZ’s

Created by Sarah Cummings

Last Updated: September 7, 2020

Sleep or exercise? Which one should you prioritize if you have to? Sleep is one of my favorite topics so I’m excited to have Sarah from The Sleep Advisor share her insights and tips on exercise and sleep deprivation. I hope it helps you to make more positive choices towards the fit and healthy lifestyle you deserve. Elly xx

Should you exercise when you are tired? Is it better to take a nap or exercise?

Among all the questions we ask ourselves in regards to our health and well-being, this is one of the most common. And it’s a tricky one. Because physical activity makes us feel good. The sweet rush of energy, the high of adrenaline, the buzz of endorphins, all make us feel refreshed and revitalised… even when an hour before we were in a lethargic slump.

So sometimes when you’re feeling tired and unmotivated, you should push yourself to work out. You’ll feel better for it.

But should you exercise when sleep deprived? Well, that’s another matter entirely.

Because sleep deprivation is more than feeling a little tired after a bad night’s sleep. It’s continuous poor-quality sleep, that affects your mood, your relationships, your work, and even your health over time. It’s not getting as much sleep as you need, every single night.

And in the case of sleep vs exercise, sleep should be the one that wins, every time.


What happens to your body when you don’t sleep

Quite simply, your body doesn’t function as it’s supposed to. For one, your weight-controlling hormones like insulin, ghrelin, and leptin are out of whack so you wind up with high blood sugar levels, middle-of-the-night cravings, and a rumbling stomach keeping you up. And come morning, a huge breakfast is the first thing on your mind, with any plans for exercise going out the window.

Elly: These examples highlight the reasons that weight loss goals become more difficult to achieve when you are chronically sleep-deprived. The hormone disruption that occurs as a result of restricted or poor-quality sleep makes regular exercise and healthy eating habits more difficult.

The research clearly highlights the links between lack of sleep, obesity, and other health conditions

Science confirms just how important a good night’s sleep is for weight loss and various areas of health. A meta-analysis of studies showed consistent links between short sleep duration and obesity. Further research suggests that the combination of inadequate sleep, disruption to physiological rhythms, and suppression of melatonin are contributing to the obesity epidemic.

With the hormonal changes that take place after a poor night’s sleep and the food choices that ensue, it’s probably not surprising that quality and quantity of sleep significantly predict the risk of the development of Type II Diabetes.

Watch the two-minute video below to hear what health and fitness expert Tom Downs says about cortisol levels during sleep, the importance of deep sleep, and why many people who are sleep deprived will struggle with fat burning.

Sleep and your immune system

Sleep also affects your immune system. While you’re busy in the land of nod, your immune system is busy producing cytokines – substances that fight off foreign invaders like bacteria and viruses. So when you don’t get enough sleep, your body produces less of these important protectors and is more vulnerable to illness. Shame.

Finally, sleep deprivation will leave you more body-tired, with heavy and stiff limbs weighing you down as your drag your weary bones into the outside world. Because no matter what kind of bed you sleep in, if you haven’t slept enough, it shows. On your face, through your words, and in every movement or action, you make.

Exercise when sleep deprived

Fitness and sleep often go hand in hand. When our bodies and minds are strong, sleep tends to come to us more easily; likewise, when we’re able to sleep better, we’re better placed to stay fit and healthy.

So you shouldn’t have to choose either sleep or exercise; they should exist simultaneously as part of your active lifestyle. However, if you are feeling the effects of sleep deprivation and are considering getting stuck into your daily workout regardless, I’d advise you to take a step back.

Ask yourself how your sleep quality has been lately (not just the previous night). Consider how your mood has been. Have you been grumpy and irritable? Finding it hard to concentrate? Unable to multi-task or to retain information? Basically, has this lack of sleep been affecting your daily life in a meaningful way?

If so, you could be sleep deprived. And I’d avoid strenuous exercise for the following reasons:

1. You’re at greater risk of injury

Even if you do a careful warm-up, a sleep-deprived body could be more prone to injury. Why? Well, you may end up pushing yourself past your limits (which your well-rested brain would never allow). Just like when you’re sick and want to get that workout in no matter what, you can take it too far. You don’t respect your boundaries, or accept the fact that maybe your body feels more stiff than usual and you should practice in a more gentle fashion. Instead, frustration and impatience spur you on and you wind up hurting yourself… all because you couldn’t decide what was more important: sleep or exercise.

So if you’ve ever asked yourself: “does sleep affect workouts?” the answer is yes, yes it can. Because without enough sleep, an impaired judgement and poorer cognitive function can lead you to forget about the importance of balance.

sleep or exercise

2. It might not be worth the effort

Since your reaction times and performance times decrease when tired, it’ll likely that working out when you’re sleep deprived will only end in disappointment. During endurance activities too, your exertion levels will be higher. So even though you might do the exact same workout as usual, you might find it a lot harder… pretty frustrating, right?!

If you’re trying to decide whether to sleep or exercise, getting some rest should be your first port of call.

3. It affects your recovery time

Like any good athlete knows, the “recovery time” between workouts is almost as important as the workouts themselves. This time is vital in terms of keeping you fit, growing in strength in a healthy manner.

But when we’re sleep-deprived, we mess up this time of tissue repair and growth. This is due to high levels of cortisol and disrupted levels of the anabolic growth hormone, creating an unfavorable metabolic environment for growth and repair. So rather than disrupting this system further or raise your cortisol levels even higher (as you would with a workout), you’re better off sleeping soundly.

Sleep and Exercise: Does exercise help sleep?

Elly: Exercising during the day can play an important role in helping you to exert energy and prepare for a restful night’s sleep. But you may be wondering “Is exercising at night bad for you”? That is, will exercise help or hinder sleep if it’s done at night?

The answer is that it depends.

Everyone is a little bit different. Some people may find that strenuous exercise at night causes them to feel energized for several hours. Therefore, it could affect their ability to fall asleep if the exercise session is too close to bedtime. Others may find that strenuous exercise in the evening helps tire them out, ready for a solid night’s sleep.

If you think that your evening or night time exercise session is affecting your ability to fall, asleep, try moving it to a little earlier in the evening. Alternatively, if you need to exercise close to bedtime and you feel like it’s affecting your sleep, stick to relaxing forms of exercise at that time (for example, restorative yoga).

Research on late night exercise and sleep

Elly: Research supports the notion that high self-perceived exercise exertion before bed is not necessarily associated with an inability to fall asleep. One study of 52 regularly exercising young adults found that high exertion exercise was associated with improved sleep, including more deep sleep, a shorter time to fall asleep, and decreased light sleep.

Sleep or exercise? Exercise or sleep?

Like I said, hopefully, you can do both. But if you’ve been feeling the effects of sleep deprivation for the past few days (or weeks), or if you’re ill/run-down, it’s always best to rest first. Listen to your body, get enough sleep, and pretty soon you’ll be on form to get back to working out.

In the meantime, here are a few tips to overcome tiredness based on some of the factors that can affect your sleep:

Set yourself an early bedtime, and stick to it

Make sure that you get between seven hours and nine hours of sleep every night. Don’t go over, otherwise you run the risk of being overtired. Rather, sleep by 10pm and you can get up at 6am, ready and refreshed for a morning workout before breakfast.

Cut down on caffeine and sugar

It might feel as if they’re getting you through the day, but they’re not. Because for every lovely high and rush, a crash is just around the corner! You should have plenty of energy based on your sleep habits, your diet, and your lifestyle. Anything you else you need to fuel this can only wind up making you feel worse in the long run. If you really need an added energy boost, try whipping up a tasty green smoothie instead!

Keep the office out of the bedroom

If you have a tendency to watch movies in bed, or check emails or update your Insta profile, your sleep is probably paying the price. You may not be aware of it, but these screens block serotonin (the ‘happy hormone’), which usually induces sleep. They also stimulate the mind instead of letting it settle down when it needs to. The result? Poorer-quality sleep and excess tiredness the next day. By shutting down early, leaving the screens outside, and reading a book instead, your sleep levels and your exercise regime will stay on track.

It’s shaping up to be a great sleep!

Now that you’ve seen how important approximately eight hours of sleep is – to your physical fitness and general health – hopefully, you’ll give it the credit it deserves. Let your exercise take a back seat while you sort your sleep out. You’ll be a more rested, more energetic person come morning.

For the days that your body IS ok to exercise, check out the FREE bodyweight workout pdf below. You can get instant access to seven bodyweight exercises that you can do anytime, anywhere.

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Sarah Cummings


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