Oura Ring: Effects of Fasting and Ultrarunning on HRV and Sleep

The One Ring to Rule Them All  

I've been wearing the Oura Ring since November 2018.  I take it off for Spartan races, rock climbing and Crossfit workouts, otherwise it doesn't get in the way of doing anything.  For those of you who haven't heard of Oura, they make a wearable ring connecting via Bluetooth to your phone, which measures activity, sleep patterns, heart rate, heart rate variability, temperature, and breaths per minute, among other things.  The app on my phone then analyses the data to let me know how it all interacts to give me a readiness score, with sage advice such as "Take it easy today, you had a hard workout yesterday and you aren't recovered yet."  or "Go big, your readiness is off the charts!"

I've been wearing it long enough now to notice some trends, and want to share some data I got during a recent 5 day fast, after eating wheat for dinner one night (I don't usually), and after a 50k ultramarathon.


Fasting

It's hardly disputed that fasting can be good for the body.   Weight loss, detoxing, etc.  But now that I am recording my own statistics, I can see the effect on my sleep, heart health, and overall readiness.  I am particularly interested in Heart Rate Variability (HRV), which is the space between heartbeats.  This shouldn't be a metronome at all...healthy people have measurable variability between heartbeats.   I started fasting the evening of Mar 11 and had a small meal the evening of March 16.

My HRV climbed to about as high as I've ever seen it

My Deep Sleep usually hovers between 30-45 minutes, but reached 1 hr 30 on the 3rd night of fasting

Respiratory Rate (Breaths Per Minute) average for me is 14.1 but dropped each night while fasted

I live at 4500 feet and usually don't see 55 beats per minute unless I travel to sea level for a few days...unless I'm fasting

Heart Rate and HRV Data from a night of fasting

Effects of Food on Sleep Scores

I haven't been eating too much gluten or carbs, by following a low-carb diet and avoiding gluten when possible.  But I ate at a friend's house and couldn't turn down potatoes, pot pie and cake for dinner.   My sleep scores that night went way down from the day before, and I hadn't exercised much  or had any other reason for lower scores.  In fact I was tapering for my 50k and didn't do much at all.   Usually when I take it easy my scores go up because of the rest and recovery factor.   Not after this meal...my average HRV and max HRV both dropped significantly.

As a side note, I've actually seen this happen before when I drink alcohol, even one drink.   Alcohol has a very depressive effect on sleep and heart rate scores, and this has been commented on by many Oura ring wearers...most of them lamenting that it greatly reduces their enjoyment of alcohol, after seeing the bad effects documented on their Oura!

Scores the night before I ate gluten

Scores from after eating gluten

Post 50k Ultrarunning Scores

My 50k took me 6 hours and I was running (or hiking uphill) as fast as possible the whole time.  Red-lining, in other words.  Slight dehydration and legs very sore afterwards.  The hardest run I've done in a while.   Here's the data the ring recorded during the day of the run

A normal, average night of sleep for me

My sleep after the 50k Run, notice I didn't get any deep sleep

                                     

Here's the same data as seen on my Oura phone app

Although I've seen enough data to know that my heart rate data is going to plummet the night after a hard run, these are the worst scores I've had in 5 months of wearing the ring.   Time will tell how many days it takes to get my numbers back up to their normal levels.  

A normal HRV graph

HRV graph after the 50k

I was amazed when I saw how flat the graphs were for both Heart Rate and HRV.  

A normal resting heart rate graph

Heart Rate graph also gets very flat

Heart Rate and HRV the night after the 50k...compare to these same graphs (above) when fasting. 

But....

....a day later, so 30 hours after the race, my heart rate and HRV bounced back A LOT, and I got good sleep scores too.  So the depressed functions aren't a long term side effect but rather an immediate change which then corrects itself.