You know the feeling: just one more episode, one more page of your book or another sleepless night of tossing and turning. No matter what, there is one likely outcome: you’re staying up too late. But how does this affect your workout? There are multiple reasons, both mentally and biologically, that explain why late nights wreak havoc on your exercise routine.


clock with sleep at night.A lack of sleep is linked to high levels of cortisol. When you have chronically high levels of cortisol—you stay up three nights in a row to finish your latest television show—leads to an inability or difficulty building muscle mass. So, even if you can drag yourself to the gym after four hours of sleep, your workout won’t be nearly as effective as if you’d had a full 7 to 8 hours.

A lack of sleep also leads to a lack of growth hormone, which is only regenerated when your body is shut down for a few hours of shut eye. Why does this matter? Growth hormone also plays an important role in muscle production, similar to cortisol—without it your workouts simply won’t be as effective.

Finally, though this may seem too obvious to state, it’s important to note that physically, a lack of sleep effects your energy levels. So, instead of pushing through the last 10 minutes of your treadmill workout, you may step off, stretch and call it a day because you’re too tired.


The morning is often when people are the most clear, sharp and at ease; even if it doesn’t feel like it as you’re slinking out of bed with the sound of an alarm beeping in the background. It’s at this time of day when you feel the least amount of anger, anxiety, and attachment, making it ideal for getting up and starting your day on the right foot, whether that’s packing for post-work gym session or getting at it right away.

Not to mention, the lack of sleep doesn’t shake off when you walk out the door; it sticks with you all day.  If you’re tired, you’re likely crabby, unmotivated and unhappy making it easier to choose comfort foods and a spot on the couch after work rather than your workout clothes and a quick post-work gym session.

Stress Management ConceptFinally, a lack of sleep leads to poor stress management. This leads to an inability to control your impulses and need to instant gratification (hello brownie, with lots of sugar and a quick shot of adrenaline). Without these abilities, any workout you do is not nearly as effective. For example, instead of making smart post-workout food choices, you may fill up on foods that only sabotage your efforts.

In the end, a lack of sleep only hurts you. Don’t let it ruin all your hard work in the gym. Get some shuteye and your workout will thank you.