🔗 Share this article

An atmosphere of building tension. I can see the frosty air coming from my fellow runners as they perform the "about to run" shuffle on the start line.

A rapid movement of the hips.

I'm at my local 5km community parkrun and I'm serious. It's almost time...

Hold on. I must adjust my tracker. So does the runner next to me.

The person in the line expresses impatience. I'm not moving until… yes! Connection established, away I go.

During the scramble, it's hard to see a arm without a fitness tracker on it. And it's not just us runners who rely on them.

This is a explosive, multi-billion pound market. Companies like Apple Watch lead the market, all offering an extensive selection of diverse devices to fit a spectrum of budgets. Depending on how advanced the model you go for, prices can vary between a hundred pounds to thousands of pounds.

"It makes me crazy, it's impossible to stop checking."

"It provides solace… It feels like a supporter guiding me."

"I wish it wouldn't say I've had a bad night's sleep."

A handful of the responses I've received from like-minded device users when I ask what they feel about theirs.

A Sea of Statistics

My thoughts on mine? Right now, frustrating. It's indicating I'm off pace, making me wonder whether the overhead branches I'm passing under are disrupting my satellite signal.

Millions of us attach these small devices onto our wrists and keep them on all day and night, ostensibly at ease with the fact they're constantly tracking us.

Long past are the days when we depended on them only to give us an rough count of our pedometer reading. Currently, they can track our sleep patterns, heart rate, glucose levels, our VO2 max.

It's a challenge to find a physical metric they don't track.

But do they do what they say they do? And are the data points we scrutinise a accurate representation of the truth? Do they improve our overall health, or do the multitude of readings and cheerleading alerts just add to our daily stresses?

Addiction or Aid?

"I find myself getting a bit fixated with mine," one user admits.

While she appreciates how her device records her workouts, she finds some of its other functions "excessive" at times - a feeling initially realised during a significant period.

Prior to discovering she could put it into a specific mode, her smartwatch constantly alerted her she was being insufficiently productive enough. Now, the watch frequently reports her she's had a restless night.

"I've got a six-month old, it's unnecessary for me to be told I've not slept," she says. "I'm acutely aware all too clearly."

Why doesn't she just stop wearing it?

"I suppose I could, theoretically, but I'm in this push-pull dynamic with it," she continues. "I appreciate it for its exercise data, but I'm unsure whether all the other things it can now do is perhaps overkill for me."

How Do They Work?

Each model of smartwatch has its own novel way of monitoring your health metrics and interpreting your data, but the vast bulk use optical sensors on the reverse of the watch.

They usually emit tiny, coloured LED lights onto your arm which can observe capillary action, detecting your pulse rate. More advanced devices measure changes in the bioimpedance that passes over the skin to get an idea of your recovery state.

The Professional Viewpoint

A data scientist says that overall for smartwatches, it's a "difficult line" - while the ever-evolving tech could actually aid early diagnosis, "identifying issues before we notice anything", it could also turn us watch wearers into the "worried well".

He points out that the most advanced wearables can perform tests like electrocardiograms (ECGs), which regularly monitor how stable the heart is. They can notify if someone is experiencing a heart arrhythmia, where there is irregular signals in the heart causing an arrhythmia.

This does not automatically signal someone is imminently going to suffer a heart attack, but it can give an advance notice they might be more at risk of a stroke in the long term.

But how to interpret these figures is complex. The expert worries that as additional features are introduced, people may find it hard to fully contextualise their data.

"I remain sceptical that having the capacity to monitor so much data is such a positive development," he says.

A clinical psychologist studying patient behaviour agrees. Her work into the impact of wearable tech on a cohort of individuals with health issues suggested a noticeable percentage of those who were given devices to monitor their condition experienced increased anxiety and were "far more likely to use medical services".

She observed a vicious circle with her patients - they noticed a concerning reading on their watch. They felt anxious. Their BPM rose. They got more worried. They re-examined the data, and their heart rate increased again.

"When people are presented with numbers about ourselves that we can't properly interpret then, naturally, we are going to want to know more," the psychologist says. "We monitor, we re-check - it becomes a vicious cycle."