“In times of stress, the best thing we can do for each other is to listen with our ears and our hearts and to be assured that our questions are just as important as our answers.”
― Fred Rogers
Many wearables in the health, wellness, and biohacking space provide users with information about their current physical state. Devices such as the Oura and Biostrap provide heart rate, respiration, and sleep quality data that gets scrutinized by the health-conscious.
But what if a wearable could actively intervene and change our physical state? Could a wearable help us feel more alert, calm, or focused? What if people could take a proactive approach and actively manipulate their state of mine? Could the Doppel device be such a tool?
The Doppel at first glance appears to be like another wearable that is making a big splash in the health, wellness, and biohacking space – The Apollo. Both devices use vibrations applied to the body to elicit a positive and intentional biological response.
With Apollo’s product being back-ordered I looked around for alternatives and stumbled upon the Doppel. While initially looking like a very similar device, the Doppel has some key differences that I will explore further in this review.
Doppel relies on psychology and neuroscience to achieve what the company calls the “Doppel effect”. The device uses a heartbeat-like vibration pattern that is either slower or faster than your resting heart rate.
The theory is that the body will entrain to this vibration, and provoke a response to either calm, focus, or energize the individual. Many of us already use music to get into the “groove” or help us focus in the gym. Doppel’s device works similarly.
(Update: I've written an extensive review of the Apollo that can be viewed HERE.)
With something as simple as a vibrating wearable, is there any actual science behind the product? Doppel’s effects have been studied in a peer-reviewed study published in Nature Scientific Reports. The test was run as a controlled, single-blind study in which volunteers were exposed to stressful social situations and then asked to report their anxiety levels.
What stressful social situation did the researchers use? Public speaking, which for many can be an anxiety-inducing endeavor. Participants wore Doppel and were told it was a device designed to measure blood pressure. Only one group of participants in the study had their Doppel units active, while the other group had theirs inactive.
After the speaking engagement, researchers analyzed the physiological arousal as well as the subjective reports of anxiety levels by study participants.
Using skin conductance response as an indicator of arousal and anxiety, and subjective reporting, the researchers concluded:
“…the results highlight that the use of doppel had a clear and significant calming effect in both physiological measures of arousal and subjective reports of anxiety during a task that is effective in inducing social stress, suggesting that doppel enabled participants to stay calmer and less anxious, as compared with the condition where the device was worn but was not performing its intended function…”
The science behind Doppel has been explored in other avenues. In one study titled, “The sound of silence is music to the heart”, researchers found that the tempo of different music types may have an impact on the heart rate and blood pressure of those listening. The results from the study are quite interesting:
“Bernardi and colleagues studied the effect of different styles and tempos of music on cardiovascular and respiratory control in both musicians and non‐musicians. They found that breathing frequency was increased by musical inputs, and that this increase was proportional to the tempo of the music.”
In another study titled “Music structure determines heart rate variability of singers” 18 healthy singers were asked to hum a single tone and breathe as needed, sing a hymn with free/unguided breathing, and sing a slow mantra.
The researchers measured the participant's heart rate continuously during these tasks. In a second case study, the researchers collected more detailed information such as respiration, skin conductance, and finger temperature. The researchers concluded:
“This means that there is a clear tendency toward an entrainment effect between singers in terms of HR acceleration and deceleration as soon as they sing a simple structure in unison.”
So, it appears that Doppel does have the science to back up its underlying method of action.
Doppel started its life as a Kickstarter project in 2015, and after raising over $100,000 is now available to the public. Doppel currently retails for USD 219.
Doppel’s website also offers an installment plan called Sezzle which can break up the total cost over several payments. Doppel comes in two colors, black or white, and offers two-strap design choices; straight or tapered. I opted for the black model with a straight band. Seeing as how I already wear a black Biostrap device, I reasoned that a white Doppel might draw more attention to my other wrist.
Doppel offers free shipping and returns within 60 days (which is a good thing, keep reading to see why). In terms of how Doppel’s price compares to its only real competition, the Apollo device is currently retailing for USD 349 and is slated to begin shipping in late May.
My Doppel unit arrived quickly from a distributor within the USA. Doppel’s main headquarters are in London, and all support or correspondence with the company is directed there. I would assume that customers living in the EU would receive their Doppel devices direct from the company’s offices in England.
Doppel arrived in a small cardboard box that is designed to resemble wood. Inside the box, I found a quick start guide, device, and charger.
There were no surprises or confusing bits to deal with and I was glad to see how straightforward the packaging presented itself. The box also contained an extra wristband “stud” that is used to secure the device strap. I found this a nice touch. The Biostrap uses a similar strap design, and one complaint that I see with regularity is that users lose the small peg that secures the strap.
Doppel reminds me of a watch, but one that is worn on the inside of the wrist instead of the outside. The band is a soft medical grade silicone and utilizes a peg to secure the strap. The housing of the actual unit itself is constructed of a matte stainless-steel housing:
Doppel discloses that the steel used contains a very small quantity of nickel but falls below nickel restrictions set by European REACH regulations. I believe this is only mentioned in the event someone with a nickel sensitivity is interested in the device.
Doppel charges on a proprietary charging base (which Doppel calls ‘bespoke’):
The unit takes about 1-2 hours to fully charge, depending on how depleted the battery is. I have found that using Doppel for 1-3 hours at a time during a typical day, the unit seems to last me 2-3 days between charges.
The Doppel website has the following to say about battery life:
“At 180 BPM and maximum intensity, the battery will last for over five hours of continuous use. At a lower BPM and intensity setting the battery will last longer. The average time with regular daily use is about 2/3 days.”
Doppel also claims their unit is IP65 rated for water resistance. IP65 should not be confused with IP67, which is the actual water submersion. Doppel’s IP65 rating is for splashes, light rain, and sweat. The rating Doppel has means that you can wash your hands, do dishes, and generally be fine. Showering, bathing, and swimming, however, are off the table!
Doppel uses Bluetooth Low Energy (BLE) to connect to a user’s smartphone. Doppel has a list of compatible smartphones on its website. The device works with iPhones 4s and later, as well as devices capable of running Android 5 & iOS 5 or later. I believe that is just about everyone’s devices these days!
Doppel recommends users let the device charge for 2 hours before first use. Charging Doppel is a bit odd, as the company has opted to use a proprietary docking unit. To charge Doppel users place the device in the charging cradle and use an elastic band that wraps over the device and secures it via two channels/grooves.
I have never seen a charging solution quite like Doppel’s, and it took me a few tries to get the unit secure enough on the charger to see the indicator light begin to glow. Doppel must have realized that this charging setup might be confusing for new users, as they have created YouTube instructional videos.
I understand the desire to not utilize micro USB, Lighting, or USB-C connectors in a device this small, but I would have liked to see some kind of induction/wireless charging similar to Oura, Biostrap, or the Apple Watch.
After letting the unit charge, my next stop was the Apple App Store to download the free Doppel app. The app requires you to sign up with an account, which is standard fare these days. After entering my email address, name, gender, birthday, and creating a password I was able to begin the pairing process.
To pair Doppel I had to remove it from the charging dock and set it back down on the dock again. The unit buzzed once, indicating pairing mode was active. After making sure I had turned on my iPhone’s Bluetooth I went inside the app and selected the “Scan” button. The app found my device, paired and I was ready to begin using Doppel.
Doppel has several pre-programmed vibration settings (energize, alert, calm, relax, focus). All the programs vibrate at different speeds, and to maximize the effectiveness of these patterns, Doppel needs to know your current resting heart rate.
The Doppel app measures a user’s heart rate by using your smart phone’s camera and flash. After placing my finger over the camera, I clicked ‘Start’ and Doppel began to measure my resting heart rate. Once completed I was able to ‘sync’ a set of pre-programmed and customized vibration patterns to the Doppel device.
Doppel lets you sync two patterns at a time to the unit. These patterns are:
After syncing a pattern set, you can manually adjust the intensity of the vibrations. Doppel’s default intensity is 20% and using a slider you can easily adjust the intensity.
The Doppel app also allows users to program their unique heartbeat vibration patterns. The app lets you drag up and down to set the beats per minute as well as adjust the intensity. You can then name and sync the custom programs to your device:
I have not experimented greatly with this function, as I trust that the patterns Doppel is programmed to use based on my RHR are optimal for my situation. I think it’s a good feature to have though, and it does work as intended.
Doppel has limited touch controls on the unit itself, allowing users to not have to be near their smartphone/device to operate it. These controls consist of tapping a pattern or sliding a finger along the surface of the device:
The controls available to users are:
While it is possible to enter pairing mode with touch control, I have found the most reliable way to enter pairing mode is to put the unit on the charging base. Why would a user need to do this? Well, that brings me to some of the ‘not so good’ things about Doppel I have experienced after using the device for several months.
On the surface, Doppel’s touch controls sound great. The execution of the controls, however, has been somewhat spotty. Sometimes I can turn the unit on and off, other times I must spend quite a few moments getting the device to switch on.
Switching between the two vibration patterns is also somewhat spotty, and only works intermittently. Doppel seems to be aware of this, as they cover troubleshooting solutions for this extensively on their website.
Another issue I had with the device was that the battery level indicator inside the app can be somewhat misleading. If I put Doppel down to charge, and I know it has a low battery, I can pick the unit off the charger and the App will tell me that it has a 100% battery. It is an odd quirk inside the app, and if I close/open the app back up it will then accurately reflect current battery percentage.
The app also sometimes does not want to connect to the unit right away, even if the device is active on my wrist. Hitting the “Sync” button usually resolves this. Sometimes when the app opens the wrong pattern is highlighted, or the on/off indicator is in the wrong position. These seem like small bugs in the app itself that could be fixed with a simple update.
Finally, I must disclose that I am on my 2nd Doppel device. The first unit I purchased unexpectedly stopped working for no apparent reason. One morning I noticed that I was unable to turn the unit on no matter how much I fiddled with the controls. Putting the Doppel on the charger also did not seem to do anything, and the unit appeared not to be taking a charge.
After pouring over the troubleshooting guides on Doppel’s website I reached out to support. To my surprise, my message was responded to within 24 hours. The person from Doppel had me try a few of the troubleshooting solutions, and then ultimately dispatched a new unit free of charge from their London headquarters. I was only asked that I send back the nonfunctional unit with a prepaid postage label they provided.
All in all, the entire exchange probably lasted two days, and within ten days I had a brand new Doppel in my hands. I returned the old unit and have not had any issues with the replacement. If I had to rate the customer service for Doppel, it would be two thumbs up.
So does Doppel work? This is a tricky question for me to answer. I can attest with 100% confidence that the “energize” and “alert” programs do indeed wake me up. Having something buzzing at 80-110 beats per minute on your wrist is bound to do that.
Does Doppel improve concentration or reduce stress? That is a bit murkier and harder to answer. I cannot honestly say with confidence that during the “concentration” sessions I felt more concentrated, in the ‘zone’ or completed more work. The device certainly did not hinder my work performance.
With regards to stress reduction using “calm” and “relax” programs, I wasn’t sure that I subjectively felt more calm or relaxed. I’m not normally a very anxious person, and I don’t suffer from anxiety attacks. It wasn’t until I sat down to write this review that I decided to see if there had been any positive trending numbers in my Oura data since I obtained the Doppel. To my surprise, there was:
My first Doppel was delivered on February 24th. Starting in March my overnight heart rate variability seems to have only gone up. This also coincides with my overall readiness score:
Looking at the numbers by month, it looks that starting in March my readiness has continued a pretty nice upward trajectory.
I have not changed my diet, workouts, or made any significant changes to my behavior or routine. I have been taking a few extra supplements, but nothing that I would attribute to a rise in HRV or readiness. Could this be the Doppel? It may be, it could also be that with spring comes more sunlight and full-spectrum light exposure.
In any case, I’m going to continue using my Doppel. It doesn’t require much in the way of maintenance. Aside from the mildly irritating touch controls and cumbersome charging dock, the device functions as intended. Doppel has also been an interesting conversation topic.
This is a tough question to answer. While both Doppel and Apollo use vibrations worn on the body to elicit a psychological and biological response, the two devices seem somewhat different.
The Apollo device isn’t currently shipping, and I wasn’t able to get my hands on a unit for testing before this review. I did, however, get to meet with representatives from Apollo Neuroscience at the Consumer Electronics Show (CES) in Las Vegas earlier this year. Click here to read my CES 2020 rundown and see my experience with the Apollo device.
From my limited hands-on time with the Apollo, that device seems to use a constant, consistent vibration instead of a heartbeat pattern like Doppel. I’m not entirely sure if one method is more effective than the other. Another major difference between these two devices is the price. The Apollo device is also over $100 more than Doppel.
In the future, I’d like to get my hands on an Apollo device and see how it stacks up against the Doppel. If both devices seem to give similar results, Doppel might be a compelling option for those not wanting to spend nearly $350 on a new wearable device.
(Here's an update on what I stated earlier: I've just reviewed the Apollo Neuro so you should be able to read my new opinion on the difference between these 2 devices now!)
The Doppel device is an interesting wearable that does more than giving users statistics about their biology. The wearable actively seeks to alter our psychological and physical state, nudging us in the desired direction. There is certainly not a lack of science to indicate that a device like Doppel might be a compelling option for nearly everyone.
There are a few important considerations I think worth mentioning before you decide if Doppel is a device worth investing in:
Price. As written about above, Doppel retails for $219. While this is certainly cheaper than Apollo’s offering, it still is not exactly cheap. What makes Doppel cost $219? The device is essentially a tiny vibrator that has a Bluetooth Low Energy (BLE) chip inside.
Many folks already own smartwatches that can vibrate, and I wonder how hard it would be to create an app you could download onto an Apple Watch to functionally do the same thing as Doppel?
Doppel also has some bugs in the software to work out, and the charging dock it uses can be a bit fiddly at times. If I am going to be away from the house and commuting, I can’t use a simple USB cord or a wireless charging mat to keep my Doppel topped off. I loathe carrying around more gear than I need, so having to remember to bring the special Doppel charger with me can be a bit of a hindrance.
If you are someone who would prefer not to take a supplement or prescription to help alleviate stress, Doppel might be an option to seriously consider. Along with weighted blankets, Doppel is another tool that doesn’t rely on medication to manage stress.
If I had to go back in time, I’m not entirely sure I’d spend the $219 I did on the Doppel device. My Oura numbers certainly have seen an upward trend, but that evidence isn’t conclusive. I can’t say with any certainty that Doppel has improved my life enough to warrant the $219 investment. With that said, I certainly don’t regret buying the device either.
With all the minor issues the device has, part of me feels like the team at Doppel never really took their product far beyond the 2015 Kickstarter stage. The device has “version 1” stamped on it, despite it now being 2020.
The app itself has seen some updates over the years, but all the bugs haven’t been worked out.
The company seems healthy, as they have a worldwide distribution from the USA and UK. The customer service was also surprisingly agile and responsive. Despite my first unit unexpectedly dying, I had a replacement in about 10 days.
The Doppel device is fun, looks great, and has compelling science behind its method of action. I’m anxious to see where devices like this go in the future and hope to get a chance to compare Doppel to the Apollo. Despite all the quirks the device has, I’ll continue to use Doppel and keep an eye on my biometric data.
This blog post was written by David Baker. David has years of biohacking experience with an emphasis on testing gadgets. He's also got 15 years of amateur bodybuilding involvement.
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