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A sense of building tension. Visible is the frosty air exhaled by my competitors as they execute the "about to run" wiggle on the starting line.

A rapid flick of the hips.

I'm at my local 5km community parkrun and I'm serious. Three, two, one...

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

The person in the line tuts. I won't start until… yes! Connection established, away I go.

In the mele, it's hard to see a arm without a smartwatch on it. And it's not just us participants who use them.

We're witnessing a explosive, multi-billion pound sector. Brands like Garmin are prevalent, each with an wide range of different models to fit a spectrum of lifestyles. According to how feature-packed the watch you choose, prices can vary between an affordable sum to thousands of pounds.

"It makes me crazy, I can't relax."

"It reassures me… It's like a supporter encouraging me."

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

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

The Monitoring Conundrum

My thoughts on my own device? Currently, frustrating. It's reporting I'm off pace, making me wonder whether the trees I'm passing under are blocking my GPS connection.

Countless individuals of us fasten these small gadgets onto our wrists and use them 24/7, ostensibly at ease with the fact they're constantly monitoring us.

Long past are the days when we depended on them exclusively to give us an estimation of our daily steps. Today, they can analyse our nightly rest, heart rate, glucose levels, our recovery score.

It's a challenge to find a bodily function they aren't designed to measure.

But can they do what they advertise? And are the numbers we analyse a faithful picture of our actual health? Do they improve our overall health, or do the plethora of metrics and constant notifications just contribute to our daily stresses?

Addiction or Aid?

"I find myself getting a bit preoccupied with mine," a wearer reveals.

While she appreciates how her device monitors her workouts, she finds some of its other features "daunting" at times - a feeling that became apparent during a significant period.

Prior to discovering she could change its configuration, her smartwatch repeatedly informed her she was failing to be active enough. Now, the watch frequently reports her she's had a restless night.

"I have a six-month old, there's no point to be informed I've not slept," she says. "I'm acutely aware only too well."

Couldn't she just take it off?

"I suppose I could, theoretically, but I have this complicated dynamic with it," she explains. "I love it for its exercise data, I just wonder whether the additional features it can now do is possibly excessive for me."

How Do They Work?

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

They typically project small, green LED lights onto your skin which can monitor blood flow, detecting your pulse rate. More advanced devices measure changes in the skin conductance that flows through the skin to get an idea of your recovery state.

A Fine Balance

A professor says that in general for smartwatches, it's a "fine balance" - while the rapidly advancing tech could realistically aid early diagnosis, "identifying issues 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 carry out tests like heart rhythm analysis, which continuously monitor how stable the heart is. They can flag if someone is experiencing a heart arrhythmia, where there is erratic impulses in the heart causing an uneven pulse.

This does not necessarily indicate someone is on the verge of a heart attack, but it can give an early warning they might be more at risk of a stroke in the future.

But how to make sense of these readings is not straightforward. The expert fears that as more functions are incorporated, people may struggle to fully understand their data.

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

A health researcher studying cardiology agrees. Her work into the influence of wearable tech on a cohort of heart condition patients suggested a minority of those who were given devices to monitor their condition experienced increased anxiety and were "more inclined to use doctor's time".

She noted a cycle with her patients - they noticed a worrying figure on their watch. They became worried. Their heart rate rose. They got increasingly anxious. They re-examined the data, and their reading rose further.

"When people are presented with stats about ourselves that we lack context for then, understandably, we are going to seek clarification," the psychologist says. "We check, we check again - it becomes a vicious cycle."