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A sense of feeling of anticipation. I can see the frosty air emanating from my competitors as they do the "pre-race" wiggle on the beginning point.

A swift flick of the hips.

I'm participating in my local 5km community parkrun and I'm focused. It's almost time...

Oh, hang on. I have to adjust my device. The same goes for the person next to me.

The person waiting expresses impatience. I refuse to go until… there! Connection established, away I go.

Amidst the crowd, it's difficult to spot a arm without a fitness tracker on it. And this isn't only us runners who use them.

It's a booming, massive industry. Brands like Apple Watch lead the market, featuring an extensive range of different models to suit a range of needs. According to how feature-packed the device you choose, prices can range from a hundred pounds to thousands of pounds.

"It drives me insane, I'm unable to relax."

"It comforts me… It's like a supporter supporting me."

"Please don't notify me I've experienced a bad night's sleep."

Just some of the comments I've had from fellow smartwatch wearers when I ask what they think of theirs.

The Monitoring Conundrum

My thoughts on mine? Currently, annoying. It's telling me my speed is wrong, leading me to doubt whether the trees I'm running below are disrupting my satellite signal.

Countless individuals of us strap these compact gadgets onto our wrists and keep them on constantly, ostensibly unconcerned with the fact they're continuously monitoring us.

Long past are the days when we depended on them solely to give us an rough count of our daily steps. Now, they can track our nightly rest, blood pressure, oxygen saturation, our VO2 max.

It's a challenge to find a health indicator they aren't designed to measure.

But can they do what they say they do? And are the numbers we analyse a accurate representation of our actual health? Do they improve our mental and physical wellbeing, or do the multitude of readings and motivational messages just contribute to our everyday anxiety?

A Complicated Bond

"I become a bit obsessed with mine," a wearer admits.

While she values how her device records her exercise, she finds some of its other features "daunting" at times - a feeling that became apparent during a major life event.

Prior to discovering she could put it into a specific mode, her smartwatch constantly alerted her she was not being energetic enough. Now, the watch frequently reports her she's had a poor sleep score.

"I am caring for a infant, it's unnecessary for me to be told I've not slept," she says. "I know that all too clearly."

Couldn't she just take it off?

"It's possible, perhaps, but I've got this complicated dynamic with it," she continues. "I love it for its exercise data, I sometimes question whether the myriad other functions it can now do is maybe too much for me."

The Technology Behind the Tracking

Every device of smartwatch has its own novel way of monitoring your health metrics and processing your data, but the vast bulk use detectors on the back of the watch.

They usually project tiny, coloured LED lights onto your wrist which can detect pulsation, identifying your heartbeat. More advanced devices analyse changes in the bioimpedance that flows through the skin to gauge your stress levels.

The Professional Viewpoint

A data scientist says that overall for smartwatches, it's a "delicate equilibrium" - while the rapidly advancing tech could potentially save lives, "detecting disease before we feel unwell", it could also turn us watch wearers into the "worried well".

He points out that some of the latest wearables can conduct tests like medical-grade monitoring, which continuously monitor how healthy the heart is. They can alert if someone is experiencing a heart arrhythmia, where there is irregular impulses 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 early warning they might be more vulnerable of a stroke in the years to come.

But how to make sense of these numbers is complex. The expert worries that as further capabilities are incorporated, people may struggle to fully understand their data.

"I'm not entirely convinced that having the capacity to monitor so many metrics is such a beneficial thing," he says.

A clinical psychologist specialising in wearable tech echoes this sentiment. Research into the effect of wearable tech on a set of heart condition patients suggested a minority of those who were given devices to monitor their condition experienced heightened worry and were "far more likely to use medical services".

She identified a cycle with her patients - they spotted a worrying figure on their watch. They became worried. Their pulse rose. They got increasingly anxious. They looked a second time, and their anxiety went up again.

"Upon viewing data about ourselves that we can't properly interpret then, of course, we are going to become concerned," the psychologist says. "We check, we re-check - it becomes a vicious cycle."