• great battery life
  • clever charging solution
  • unobtrusive – you forget that you’re wearing it
  • good data visualisation
  • can transmit bluetooth and replace your HRM chest strap


  • limited access to raw data
  • some might dislike the subscription business model
  • some strap materials allow the device to flip too easily
  • optical HRM struggles at high heart rates (200bpm+)

In my meandering journey through the tech startup world, one of the many ideas I flirted with was to leverage my dual ‘expertise’ in sports and tech to create a device which you would wear all the time and it would, by measuring your heart rate, heart rate variability, and movement, tell you not only how hard you trained, but also how recovered you are. Something that isn’t emphasized enough to aspiring sportspeople is that rest is a very important part of training, and given the opportunity, most motivated individuals will generally train too much and either injure themselves, get sick, or burn out.

While listening to one of my favourite podcasts – the Velonews “Fast Talk” podcast, I learned that the device I described has already been made, and it is called the Whoop. In fact, they had just released the third iteration of their strap and among the many incremental improvements one expects from successive iterations of products, the whoop strap 3.0 boasts a significant jump in battery life (about 5 days. up from 2), and is capable of transmitting its heart rate information over bluetooth in the same way that a regular heart rate monitor does. The latter feature is what ultimately won me over, since many of my common training frustrations include such things as forgetting to bring my chest strap heart rate monitor (HRM), or putting on my skating suit then realising that I had not yet put on my chest strap HRM.

Originally, the Whoop was intended as a wrist-worn device which would, in an athlete’s workflow, work alongside her other systems (typically a GPS watch and paired HRM strap). The ability for the strap to transmit HR data on bluetooth means that she can effectively replace a clumsy chest strap that she has to remember to bring to every training with a wrist strap which she would always have on her. Observant readers are probably wondering why I didn’t just get a fitbit. The fact is, I have a fitbit but don’t use it for anything to do with sports because, after much testing, I have determined that a wrist-worn optical HRM isn’t accurate or consistent enough for my uses, and at the time I got the Whoop, I was using my fitbit solely as a sleep monitor. One of the nice things about the Whoop that, since it isn’t designed to be used as a watch, it can also be worn on the upper arm. This is what I do, since the readings are far more accurate and consistent. Using it this way is refreshingly unobtrusive and convenient.

Of course, Scosche and Polar both make broadly-compatible armband-style heart rate monitors, so what does Whoop offer that they don’t? Well both of those (and indeed most dedicated ‘sports’ HRMs) are only designed to measure heart rate during a workout. As an answer to Fitbit, Garmin also does 24/7 heart rate monitoring, as does the Apple watch, but what Whoop does is it takes this data and tells you how hard your day was, how well you slept, and it also gives you a “recovery score”. The daily strain score is especially useful to serious athletes because they spend a lot of time right on the edge of being overtrained, and knowing how difficult the rest of your day is (when you’re not training) can give you valuable and, importantly, actionable information on how hard or easy you should train. The recovery score is a measure of how much neurological strain you’re under and is calculated using heart rate variability during your slow wave phase of sleep. Why only during slow wave sleep (SWS)? Simply so that there is a consistent, repeatable, and comparable data point from one day to the next.

As a surprise bonus, this is one of the most accurate sleep monitors I’ve ever used. Not many people know this, but I’ve had difficulties with sleep throughout my life so I try to monitor my sleep so I can pick up problems early on, before they become big problems. I used a Beddit for quite a while and it was pretty good, but the devices are very sensitive and (1) don’t last, and (2) don’t travel well (it’s a strap that you put between your bedsheets and the mattress), before that I used a Zeo sleep monitor which was a strap you wore around your head, but the company went bust, and more recently I used a Fitbit, even after I switched to using a Nokia watch (the Nokia theoretically did sleep monitoring, but it wasn’t accurate, and I would give a similar criticism for my current Garmin watch). The Whoop is able to detect when you fall asleep and when you wake up, and can also detect short naps.

All together, the Whoop offers a compelling package. In terms of impact, I rate it very highly – it has significantly changed the way that I train. Being able to see my heart rate variability,  as well as my resting heart rate, as well as my sleep gives me an excellent idea of how tired I am, and how hard I should train. It has helped me make adjustments to training programs to optimise certain ‘priority’ workouts around time periods with high recovery. The data is also useful for detecting illness before any obvious symptoms show up (low HRV is an early indicator of illness, and often shows up before elevated resting heart rate, which is another early indicator), so you can scale back the training load or take a day off to prevent having to take many days off, or going deep into overreach and then screwing up your training program. The data also tells you when you’re well-rested, and indeed when you’re physically peaked, and this information has obvious implications for designing training programs.

The user interface is well-designed, and built around using the smartphone app as the primary means to interface with the device. There is also a web interface with which you can view even more of your data (it mostly takes advantage of greater screen real estate to display graphs over a longer time period). There is some integration with platforms like TrainingPeaks – for example I can export sleep and recovery metrics (time slept, time in deep sleep, recovery score, HRV, RHR) to my TrainingPeaks account, but there’s no real integration with any of the “training” parts of TrainingPeaks. This is only a small quibble, but it would be nice if for example, if my watch drops the HRM signal, or runs out of battery, I could specify the start and end times in TrainingPeaks, and it could fetch the HR info from Whoop and then calculate the appropriate training stress score. I’ve had to manually do this a few times, and it wouldn’t be a difficult thing to tell a computer to do.

The image on the top-right is the starting screen. One swipes to the left to reveal day strain, recovery, and sleep, and from any of these four screens, swipes down for more detail. Turning your phone on its side will reveal your heart rate for the day. If for whatever reason the app doesn’t detect an activity or a nap, it is easy to manually enter it.

On a ‘proper’ computer, you can view more data at a time, and this can be very useful when considering how you’ve been performing with regard to an annual plan, and can give you a great overview of how well you’re responding to training.

In practical terms, the charger is well thought-out. It clips over the strap in such a way that you don’t have to remove the strap while it is charging which is a huge plus. The second wonderful thing about the charger is that it is, in fact, a small battery, so you can charge the charger via a regular USB port, then at some later, more convenient time, clip the charger onto your whoop. Other sports device companies should take note. The only downside to the charger is that it isn’t waterproof (not that I would have expected this, but the whoop itself is waterproof, so one must take care not to accidentally take a shower while the charger is clipped on). One of the only other downsides is that, as an optical HRM, the Whoop struggles with very high heart rates (I already wear it on my bicep rather than my wrist to help it get better readings). Fortunately, in my old age, I rarely go over 200 (this used to be a very common occurrence, and I would regularly spend a lot of time at 220-230, and peak at 250) so this hasn’t been a problem, but any athletes out there who have high maximum heart rates might want to take note. The only other thing is that certain band materials (you can choose from a number of different ones) allow the device to flip very easily, e.g. when you take your shirt off to put your skating suit on. I recommend the “proknit” band or the “hydro” band (intended for swimming) as they are the least stretchy of the available materials.

I highly recommend the Whoop. The data it provides and the way in which it is delivered have made a significant impact to the way I train and, I believe, has added significant value to my training. With a kid in daycare, and limited time to train, it is important to me to make the absolute most out of my training sessions and that means knowing how well-rested I am, how hard I trained, and how well I’m recovering. In terms of target audience, it skirts the fine line between fitness enthusiast and elite athlete with elements of the user interface clearly aimed at one or the other, but it’s clear that the people working on the nuts and bolts behind the scenes are very much building a device for elite athletes, and that is where I believe there is the most value to be had. That does not mean that there isn’t anything for the fitness enthusiast though, there’s plenty of good training advice given in the feedback given by the app, as well as a lot of little tips on how to sleep better. In fact, the device is worth it for the sleep metrics alone – consistent, good quality sleep is obviously essential for athletic performance, but (and this is intuitively obvious) getting good sleep is essential for general health as well. More and more studies are coming out piling on the evidence that poor sleep is linked to a plethora of health problems, as well as physiological metrics which are barely perceptible but over time can make a huge difference – e.g. reaction times. For example, sleeping one hour less than normal each night for a only week slowly degrades cognitive function to the level of staying awake for 24 continuous hours. The Whoop app calculates how much sleep you need based on all the data it collects (a high day strain score will increase your sleep need) and even keeps track of how much sleep debt you’ve accumulated over time. Many tech startups claim to want to make the world a better place, but in terms of impact, if Whoop can succeed in making a significant number of people (athletes or non-athletes) sleep better, then they will have succeeded more than most.

On a final note, Whoop has gone with a subscription business-model which I’m currently a bit ambivalent about. On the one hand, we’re used to paying a big upfront cost for a device, and then enjoying the ‘service’ they provide for free. But now with the ‘service’ coming to include a lot of cloud-based analytics, and continual software updates (thank goodness) to fix bugs, improve data security, and add functionality, it’s not entirely unfair to charge people on an ongoing basis – servers and bandwidth do cost money, after all. In all honesty, I would be happy to pull the raw data directly from my device and analyse it myself, thus negating the need for their analytics and ongoing payment, but I recognise that not everyone has the time or desire to do that, and that most people will get an enormous amount of value from the service that they provide. Indeed, this might be the future of sports wearables, because increasingly it isn’t the data, but the analysis and interpretation of that data which is where the value comes from, and that kind of ongoing value provision will require ongoing payment to be sustainable.

post script: the Whoop company produces a podcast which is fairly hit-and-miss in terms of quality. It’s worth going through them and picking out the ones which feature Emily Capodilupo in them, as she’s head of data science in Whoop. Kristen Holmes is another person to look out for in the Whoop podcast.

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