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There's a building tension. I can see the chilled vapour exhaled by my fellow runners as they do the "about to run" wiggle on the beginning point.

A swift movement of the hips.

I'm lined up for my local weekly parkrun event and I'm serious. Three, two, one...

Hold on. I need to adjust my watch. As does the guy next to me.

The person in the line sighs. I refuse to go until… yes! Connection established, I'm off.

In the mele, it's challenging to see a wrist without a fitness tracker on it. And it's not just us runners who wear them.

We're witnessing a booming, multi-billion dollar industry. Names like Samsung Galaxy dominate, featuring an wide selection of diverse versions to suit a variety of budgets. Depending on how high tech the watch you select, prices can start from a hundred pounds to a small fortune.

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

"It reassures me… It acts as a supporter encouraging me."

"Please don't notify me about a bad night's sleep."

A handful of the comments I've had from other device users when I inquire what they think of theirs.

The Data Dilemma

My current opinion on mine? Right now, annoying. It's reporting I'm off pace, causing me to question whether the foliage I'm passing under are interfering with my GPS connection.

A vast number of us attach these compact gadgets onto our arms and use them constantly, ostensibly unconcerned with the fact they're constantly tracking us.

A distant memory are the days when we depended on them only to give us an estimation of our pedometer reading. Now, they can analyse our sleep patterns, stress levels, glucose levels, our recovery score.

It's tricky to find a health indicator they don't track.

But are they able to do what they say they do? And are the statistics we scrutinise a faithful picture of our actual health? Do they enhance our daily wellness, or do the multitude of measurements and cheerleading alerts just increase our everyday anxiety?

A Complicated Bond

"I become a a little obsessed with mine," an individual confesses.

While she values how her device records her exercise, she finds some of its other features "daunting" at times - a feeling initially realised during a significant period.

Until she found out she could put it into a specific mode, her smartwatch repeatedly informed her she was being insufficiently energetic enough. Later on, the watch frequently reports her she's had a restless night.

"I've got a infant, it's unnecessary for me to be notified I'm tired," she says. "That fact is all too clearly."

Why doesn't she just stop wearing it?

"It's possible, I suppose, but I'm in this complicated dynamic with it," she continues. "I appreciate it for its fitness insights, I sometimes question whether all the other things it can now do is perhaps too much for me."

The Technology Behind the Tracking

Each model of smartwatch has its own proprietary way of tracking your health metrics and processing your data, but the most use optical sensors on the reverse of the watch.

They usually project tiny, coloured LED lights onto your arm which can observe pulsation, identifying your BPM. Higher-end devices detect changes in the skin conductance that flows through the skin to gauge your nervous system activity.

The Professional Viewpoint

A data scientist says that overall for smartwatches, it's a "delicate equilibrium" - while the ever-evolving tech could actually prevent illness, "detecting disease before we feel unwell", it could also turn us the tracked into the "concerned but fine".

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

This does not necessarily indicate someone is imminently going to suffer a heart attack, but it can give an advance notice they might be more susceptible of a stroke in the future.

But how to understand these figures is complicated. The expert fears that as further capabilities are introduced, people may struggle to fully contextualise their data.

"I'm not entirely convinced that being able to monitor so many things is such a beneficial thing," he says.

A clinical psychologist specialising in cardiology concurs. Her work into the impact of wearable tech on a specific group of individuals with health issues suggested a significant portion of those who were given devices to monitor their heart health experienced heightened worry and were "more inclined to use medical services".

She identified a pattern with her patients - they noticed a alarming metric on their watch. They felt anxious. Their BPM rose. They got increasingly anxious. They re-examined the data, and their reading rose further.

"Upon viewing stats about ourselves that we don't really understand then, of course, we are going to become concerned," the psychologist says. "We monitor, we re-check - it becomes a vicious cycle."