The Afterburner Effect - Can late night exercise sabotage your sleep quality?

One of the most discussed topics amongst hard working professionals is:

"My schedule is already so packed...when should I do my exercise?".

Well, current science suggests there is no one universal time of day that is best to exercise for sleep. Rather, the optimal exercise time likely depends on individual factors such as your chronotype, your age, and any underlying health conditions.  

That's of course not the answer you were looking for, so let's first see how exercise in general can influence your sleep.

How Does Exercise Influence Sleep?

Regular exercise, and even short bouts of exercise, can   lead to improvements in total sleep time, sleep quality, and time spent falling asleep. Exercise may also help reduce the symptoms of sleep disorders such as sleep apnea or sleep-related movement disorders like restless legs syndrome.

Aerobic exercise in the morning or afternoon stimulates earlier melatonin release and shifts the circadian rhythm forward. For people who exercise outdoors, morning exercise may have the added benefit of exposure to sunlight. This helps stabilise circadian rhythms and makes it easier to fall asleep early.  

Research has found that evening exercise may negatively affect sleep quality for early birds, but not for night owls.  This may be one reason why certain people have no trouble exercising at night, while others struggle to sleep afterward.

So yes, exercise during the day has a huge positive impact on sleep quality. But what about trying to push in a late night evening workout? Is it good or bad?

Does Working Out Before Bed Make It Harder to Sleep?

In preparation for sleep, body temperature drops, heart rate slows, and brain waves get slower. By contrast, exercise leads to a rise in core body temperature, an increased heart rate, and higher levels of arousal that can hinder sleep. Because of these physiological processes, your sleep quality can be negatively impacted when having a late night workout.

I have been testing a lot with exercise timing and the impact of it on my sleep. Recently, I was doing an intense running test in the evening while I was also tracking my HRV and sleep quality.

I started my test around 7.15 PM and finished around 8 PM. (blue bars)

You might notice that right after the test, my autonomic nervous system was still very active (high red bars) and I could only reach some relaxation two hours after I have finished the test.

Additionally, during my first hour of sleep (starting at 11 PM), although I was sleeping, my body was still activated (small red bars) and recovering from the intensity of the exercise.

So even while I finished my intense workout 3 hours before bedtime, my first sleep stage was still affected by the intensity of the workout.

As a consequence, my sleep was less qualitative than it should have been.

My recommendations

• Yes, exercise is good. Try to do   at least 150 minutes of moderate intense exercise during the week, divided in 30 minute sessions
• A   high intensity workout in the morning is good to kickstart your cortisol and it stimulates your melatonin release in the evening
• Although it is very personal,   high intensive workouts in the evening are to be avoided  during the last hours before bedtime.

Based on my experience working with many different professionals, I would not advice to do intense exercise 3 hours before bedtime.

Try to test different hours during the day to see what works for you (and be cautious of doing intense workouts in the evening).

Monitoring your body's stress levels and sleep quality after a workout can help you to better understand your physiology and adapt your schedule based on your personal situation.

Keep on moving!

Lieven