Recently, I purchased a Garmin watch (because it would seem you aren’t a real runner without a Garmin!!), upgrading from my Samsung Activ2, which I loved, but sadly, the battery life wasn’t up to a marathon.

I’ll be honest and say I have been disappointed.

Waking up that first morning, having worn my new watch overnight, I felt alert and well-rested. Garmin, however, had other plans, reporting a sleep score of 75 and suggesting, ‘You might feel tired today. Take it easy.’ The irony is that as I process this information, I feel deflated and a little annoyed, only to see my stress score go up as a result!

Since then, I have slowly moved away from using the ‘whistles & bells data’ that the higher price tag promised me, favouring asking myself how I feel instead of checking my body battery. But I know many feel drawn to their health & performance stats and enjoy the gamification that they bring. I love a pretty heart rate graph too!

So, what’s it all about?

Are these wearables the answer to our long-term health and well-being, the secret to improving our fitness, and if so, what data should we be using?

Here are 5 key points from the pod that I found most useful:

1.      Heart rate is poorly detected by a wrist monitor & should not be relied upon when exercising. Use a heart rate chest or arm strap if you’re interested in this data.

2.      Tech companies can change the algorithms that are used to give you scores, like sleep, stress, body battery & readiness to train, and are kept highly secret.  This means your data could suddenly change because they have changed the equation they use to arrive at that number. It also means devices cannot be compared to each other.

3.      No device can accurately measure sleep. Only brain electrodes can do this. Wearable devices use movement, which is highly inaccurate, and it certainly cannot accurately detect sleep stages. So don’t lose sleep over it!

4.      Recovery or readiness to train scores are missing key information, using heart rate to infer intensity doesn’t account for a tough strength session, leaving you with muscle soreness, an important component of how ‘ready’ you feel & physically are ready to train.

5.      VO2 max & lactate thresholds are guestimates and taken from generalised population data. You need lab-based tests, that include blood testing to provide you with these scores.

I know I’m being very negative, so here are 3 positives to these devices that I think will also save you from injury:

1.      Accountability when it comes to sleep. As you know I am a BIG advocate for sleep when it comes to injury prevention and recovery. It is one of the most effective components you can prioritise if you want to avoid injury or recover more quickly, so, if your watch helps you stay accountable, promotes better sleep hygiene and therefore sleep quality then I’m all for it.

2.      Sessional goal setting that helps you stick to your plan. Uploading a pre-written plan to your watch can ensure you periodize your training. Easy sessions are easy and hard sessions are hard. Consistently spending too much time in the middle ‘race pace’ zone is where injuries occur.

3.      Analysis of cadence. Your stride rate is a useful piece of data with a lower cadence linked to higher leg stress and potential for injury. This metric is most beneficial to assess post-run to conclude the effects of a training intervention, rather than being used during the session.

All the above points require you to have some handle on the data. Whether that’s understanding there are inaccuracies or knowing your training zones. But please remember, you know your body better than any device. Use it to help guide your decisions, don’t put it in control.

References

Edwards WB, Taylor D, Rudolphi TJ, Gillette JC, Derrick TR. Effects of stride length and running mileage on a probabilistic stress fracture model. Med Sci Sports Exerc. 2009 Dec;41(12):2177-84. doi: 10.1249/MSS.0b013e3181a984c4. PMID: 19915501.

Schubert AG, Kempf J, Heiderscheit BC. Influence of stride frequency and length on running mechanics: a systematic review. Sports Health. 2014 May;6(3):210-7. doi: 10.1177/1941738113508544. PMID: 24790690; PMCID: PMC4000471.