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An atmosphere of feeling of anticipation. I can see the cold breath exhaled by my rivals as they do the "about to run" wiggle on the start line.

A rapid flick of the hips.

I'm lined up for my local 5km community parkrun and I'm focused. It's almost time...

Wait a second. I must adjust my device. As does the guy next to me.

The person behind us tuts. I'm not moving until… done! GPS ready, I'm off.

During the scramble, it's hard to find a arm without a fitness tracker on it. And this extends beyond us runners who wear them.

This is a thriving, massive market. Companies like Apple Watch lead the market, each with an extensive selection of diverse devices to suit a range of lifestyles. Depending on how advanced the model you select, price tags can vary between £100 to a small fortune.

"It makes me crazy, I'm unable to stop checking."

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

"Stop telling me I've had a restless night."

A small sample of the reactions people have shared from fellow device users when I ask what they feel about theirs.

A Sea of Statistics

My thoughts on my own device? Right now, irritating. It's indicating my speed is wrong, causing me to question whether the foliage I'm passing under are disrupting my location tracking.

A vast number of us fasten these little devices onto our wrists and wear them all day and night, ostensibly comfortable with the fact they're perpetually monitoring us.

Long past are the days when we depended on them exclusively to give us an idea of our pedometer reading. Currently, they can track our sleep quality, heart rate, heart rate variability (HRV), our recovery score.

It's a challenge to find a health indicator they fail to monitor.

But do they do what they advertise? And are the statistics we analyse a true reflection of our actual health? Do they improve our daily wellness, or do the multitude of measurements and motivational messages just add to our sense of overwhelm?

A Complicated Bond

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

While she loves how her device monitors her runs, she finds some of its other functions "overwhelming" at times - a feeling first discovered during a major life event.

Before she realised she could adjust the settings, her smartwatch kept telling her she was not being active enough. In a new phase, the watch frequently reports her she's had a bad night's sleep.

"I am caring for a young baby, I don't need to be notified my sleep was poor," she says. "I know that all too clearly."

Couldn't she just remove it?

"I could, I suppose, but I have this complicated dynamic with it," she says. "I love it for its exercise data, but I'm unsure whether the myriad other functions it can now do is perhaps overkill for me."

The Technology Behind the Tracking

Each model of smartwatch has its own unique way of monitoring your vitals and analysing your data, but the vast bulk use sensors on the underside of the watch.

They typically project tiny, coloured LED lights onto your wrist which can monitor blood flow, recording your pulse rate. More advanced devices measure changes in the skin conductance that flows through the skin to gauge your recovery state.

The Professional Viewpoint

A professor says that overall for smartwatches, it's a "difficult line" - while the rapidly advancing tech could realistically prevent illness, "spotting abnormalities before we show symptoms", it could also turn us the tracked into the "worried well".

He points out that the most advanced wearables can conduct tests like heart rhythm analysis, which constantly monitor how healthy the heart is. They can flag if someone is experiencing atrial fibrillation (AF), where there is irregular electrical activity in the heart causing an uneven pulse.

This does not automatically signal someone is on the verge of a heart attack, but it can give an preliminary indication they might be more vulnerable of a heart problem in the long term.

But how to understand these readings is complex. The expert worries that as more functions are added, people may find it hard to fully understand their data.

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

A professor studying patient behaviour concurs. 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 cardiac function experienced increased anxiety and were "far more likely to use healthcare resources".

She identified a pattern with her patients - they saw a concerning reading on their watch. They became worried. Their pulse rose. They got increasingly anxious. They checked again, and their anxiety rose further.

"When people are presented with stats about ourselves that we don't really understand then, naturally, we are going to want to know more," the psychologist says. "We look, we obsess - it becomes a self-fulfilling prophecy."