I Swam Twice a Week for 3 Weeks. Here’s What It Meant for My Sleep

The house I grew up in sits directly across the street from my hometown's swimming pool. Needless to say, most summers were spent in the water -- from playing with friends and taking swim lessons to then becoming a swim instructor, lifeguard and competitive swimmer.

It's no surprise, then, that I enjoy being in and around water, whether a pool, lake or ocean -- and it turns out that this enjoyment is backed by science, too. You may have heard of a "blue prescription" or the Blue Mind Theory, popularized by marine biologist Wallace Nichols. These theories suggest that there are intrinsic beneficial connections between humans and water. Being around water or “blue space” has been proven to increase dopamine, serotonin and oxytocin in the brain and decrease cortisol levels, which lowers heart rate and stress levels. 

Initial thoughts and expectations

For this experiment, I wanted to investigate the impact of swimming and being around water on my sleep quality. Unfortunately, I don't live near an easily accessible natural body of water such as a lake or ocean. I do, however, live near an indoor pool, where I decided to take up lap swimming. 

I dove headfirst into this investigation, assuming, for a few reasons, that I would sleep better on the days I swam. Not only does being around water have a naturally calming and meditative effect, but swimming is also an excellent form of exercise and has many known benefits -- including better sleep. 

I spoke with licensed psychotherapist and sleep specialist Annie Miller, who explained that movement and exercise increase the body's natural sleep drive, which allows us to feel sleepier and have overall better sleep quality, and swimming is no exception. 

"Swimming is an activity that promotes deeper, more mindful breathing, which encourages relaxation. Deep breathing can positively impact sleep quality," said Annie. 

Let's be clear: I'm no scientist, but I did my best to keep other variables the same. I limited my coffee consumption to two cups in the morning and kept my diet similar each day, including what and when I ate. I didn't drink alcohol and took the same sleep gummies every night. I also did not engage in any other forms of strenuous exercise on the days when I did not swim.

I swam a consistent distance of 1 mile each swim day. The only difference was the speed at which I completed the mile, which ranged from 38 to 40 minutes. I tracked my workouts and sleep data using my Apple Watch and waited until the end of the trials to compare and contrast the information to avoid potentially swaying the results prematurely. Right off the bat, however, I noticed that my sleep quality seemed worse on the nights after swimming versus days when I didn't swim.

Swimming vs. sleep data

The results

The final results of this experiment shocked me: On average, I actually slept less and was awake more on swim days compared to non-swim days -- essentially the opposite of what I was expecting to find. 

Sleep on swim days vs. non-swim days

I also noticed an interesting pattern with my sleep when comparing swim days with the off-days immediately following a swim day, or what I'll refer to as a "recovery day." On swim days, my total sleep time averaged just under 7 hours, and my awake time was about an hour per night. On recovery days, my total sleep time was much higher -- around 8.5 hours, with a significantly lower awake time of about 30 minutes. 

Sleep on swim days vs. recovery days

To be honest, I was baffled. I read online to see if others have had a similar experience and found the probable cause. According to writer and competitive swimmer Olivier Poirier-Leroy, the more intense the workout, the harder it can be to sleep due to the spiked cortisol and norepinephrine (adrenaline) levels. In fact, it can take up to 48 hours for norepinephrine levels to return to normal after high-intensity exercise -- which seemed to be the case for me.

Consistently walking out of the swim center with wobbly pool noodle legs was probably a sign that I was pushing myself a little too hard. Despite not having the results I had expected (or hoped for), I noticed a few other interesting changes during this experiment that are harder to quantify but worth mentioning. 

My stress floated away

My lap swim sessions occurred in the middle of my workday, around 1 p.m. Every time I left for the swim center, I felt sluggish and stressed about going when I had other tasks to complete. Some days, I even had an accompanying tension headache before swimming and was generally not looking forward to the workout. 

During the workout, those negative feelings would gradually wash away. I began looking forward to reaching that meditative state where I could focus solely on breathing and calming my mind.

After every swim, I noticed a significant improvement in my mood. I was less stressed and didn’t experience that typical afternoon slump when I usually opted for another cup of coffee to get me through the rest of the day. I felt physically tired but mentally energized and focused, ready to tackle the rest of the day’s to-do list. 

Conclusion and final thoughts

I believe being in and around water had positive calming effects, as the Blue Mind Theory suggests, but perhaps not quite enough to outweigh the spiking cortisol levels I was experiencing from pushing myself too hard. 

Like Finding Nemo’s Dory says, I’ll “just keep swimming” using the insight gained from this experiment until I find a happy medium that improves my sleep quality. I hope to conduct similar studies with less intense workouts or simply spend time near water each day to explore these theories further. 

If you’re like me and you’re looking for ways to get better rest, don’t sleep on our simpler tips and tricks, such as limiting technology usage, developing a bedtime routine, journaling or meditating and -- take it from me -- making sure you’re working out at an appropriate intensity level and at the right time of day.