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A sense of feeling of anticipation. I can see the cold breath exhaled by my fellow runners as they do the "pre-race" jiggle on the beginning point.

A quick flick of the hips.

I'm participating in my local weekly parkrun event and I'm focused. The countdown begins...

Hold on. I have to adjust my device. So does the guy next to me.

The person behind us expresses impatience. I'm not moving until… there! GPS ready, away I go.

In the mele, it's hard to see a person without a fitness tracker on it. And this extends beyond us participants who use them.

This is a booming, multi-billion pound sector. Brands like Apple Watch dominate, each with an extensive selection of various versions to suit a variety of needs. Depending on how feature-packed the device you select, price tags can range from an affordable sum to a significant investment.

"I find it infuriating, I'm unable to switch off."

"It comforts me… It feels like a supporter guiding me."

"Stop telling me I've had a bad night's sleep."

A small sample of the reactions I've received from like-minded smartwatch wearers when I ask what they think of theirs.

The Monitoring Conundrum

My thoughts on mine? At this moment, annoying. It's reporting I'm off pace, leading me to doubt whether the foliage I'm running below are disrupting my GPS connection.

Millions of us attach these little monitors onto our arms and keep them on 24/7, apparently unconcerned with the fact they're perpetually recording us.

A distant memory are the days when we used them solely to give us an estimation of our step count. Today, they can analyse our sleep quality, stress levels, heart rate variability (HRV), our recovery score.

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

But can they do what they claim to do? And are the statistics we obsess over a faithful picture of our actual health? Do they boost our mental and physical wellbeing, or do the avalanche of readings and constant notifications just increase our sense of overwhelm?

A Complicated Bond

"I become a quite preoccupied with mine," one user reveals.

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

Until she found out she could adjust the settings, her smartwatch kept telling her she was not being productive enough. Now, the watch insists her she's had a bad night's sleep.

"I've got a infant, I don't need to be notified I've not slept," she says. "I know that perfectly well."

Is it not possible to just take it off?

"I could, theoretically, but I'm in this complicated dynamic with it," she explains. "I love it for its workout tracking, I just wonder whether the myriad other functions it can now do is perhaps excessive for me."

How Do They Work?

Different brands of smartwatch has its own proprietary way of tracking your health metrics and analysing your data, but the vast bulk use detectors on the reverse of the watch.

They usually project minute LED lights onto your arm which can monitor blood flow, detecting your heartbeat. Higher-end devices measure changes in the skin conductance that runs through the skin to gauge your recovery state.

The Professional Viewpoint

One expert says that overall for smartwatches, it's a "difficult line" - while the ever-evolving tech could potentially aid early diagnosis, "identifying issues before we show symptoms", it could also turn us device users into the "concerned but fine".

He points out that some of the latest wearables can perform tests like electrocardiograms (ECGs), which continuously monitor how stable the heart is. They can flag if someone is experiencing a heart arrhythmia, where there is irregular electrical activity in the heart causing an irregular heartbeat.

This does not automatically signal someone is imminently going to suffer a cardiac event, but it can give an preliminary indication they might be more susceptible of a stroke in the future.

But how to interpret these numbers is complicated. The expert fears that as more functions are introduced, people may find it hard to fully contextualise their data.

"I remain sceptical that being able to monitor so much data is such a positive development," he says.

A health researcher studying patient behaviour echoes this sentiment. A study into the impact of wearable tech on a cohort of heart condition patients suggested a noticeable percentage of those who were given devices to monitor their condition experienced heightened worry and were "had a higher tendency to use medical services".

She observed a pattern with her patients - they noticed a alarming metric on their watch. They grew concerned. Their pulse went up. They got more worried. They looked a second time, and their reading increased again.

"If we see data about ourselves that we lack context for then, naturally, we are going to become concerned," the psychologist says. "We check, we check again - it becomes a vicious cycle."