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A sense of building tension. Apparent is the cold breath coming from my fellow runners as they do the "starting line" shuffle on the beginning point.

A swift twitch of the hips.

I'm participating in my local weekly parkrun event and I'm serious. It's almost time...

Oh, hang on. I need to adjust my tracker. As does the person beside me.

The person waiting tuts. I refuse to go until… there! Signal acquired, away I go.

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

It's a booming, multi-billion dollar sector. Companies like Apple Watch dominate, all offering an wide range of various devices to suit a range of lifestyles. Depending on how high tech the model you go for, costs can vary between an affordable sum to a significant investment.

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

"It comforts me… It's like a companion encouraging me."

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

A handful of the responses I've had from other device users when I ask what they feel about theirs.

The Data Dilemma

My current opinion on my own device? Right now, irritating. It's indicating I'm not hitting my target, leading me to doubt whether the foliage along my route are blocking my location tracking.

Millions of us strap these compact devices onto our wrists and wear them 24/7, apparently unconcerned with the fact they're perpetually recording us.

Gone are the days when we relied on them solely to give us an rough count of our step count. Now, they can track our sleep quality, heart rate, heart rate variability (HRV), our VO2 max.

It's tricky to find a physical metric they fail to monitor.

But do they do what they say they do? And are the statistics we scrutinise a accurate representation of reality? Do they boost our mental and physical wellbeing, or do the avalanche of measurements and cheerleading alerts just add to our daily stresses?

A Complicated Bond

"I do get a quite preoccupied with mine," an individual confesses.

While she appreciates how her device tracks her workouts, she finds some of its other capabilities "daunting" at times - a feeling initially realised during a major life event.

Before she realised she could adjust the settings, her smartwatch constantly alerted her she was not being energetic enough. Later on, the watch insists her she's had a bad night's sleep.

"I am caring for a six-month old, I don't need to be informed I've not slept," she says. "That fact is perfectly well."

Couldn't she just remove it?

"I suppose I could, theoretically, but I have this push-pull dynamic with it," she continues. "I love it for its fitness insights, but I'm unsure whether all the other things it can now do is perhaps overkill for me."

The Technology Behind the Tracking

Different brands of smartwatch has its own proprietary way of measuring your bodily functions and analysing your data, but the majority use optical sensors on the back of the watch.

They commonly shine tiny, coloured LED lights onto your arm which can monitor capillary action, recording your BPM. Higher-end devices analyse changes in the bioimpedance that runs through the skin to get an idea of your nervous system activity.

The Professional Viewpoint

A professor says that overall for smartwatches, it's a "difficult line" - while the continuously improving tech could realistically save lives, "spotting abnormalities before we notice anything", it could also turn us the tracked into the "worried well".

He points out that some of the latest wearables can carry out tests like electrocardiograms (ECGs), which regularly monitor how normal the heart is. They can alert if someone is experiencing an irregular rhythm, where there is abnormal impulses in the heart causing an irregular heartbeat.

This does not mean someone is about to have a cardiac event, but it can give an advance notice they might be more at risk of a stroke in the long term.

But how to interpret these numbers is complex. The expert concerns that as more functions are incorporated, people may struggle to fully comprehend their data.

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

A health researcher studying cardiology agrees. A study into the impact of wearable tech on a specific group of heart condition patients suggested a minority of those who were given devices to monitor their condition experienced increased anxiety and were "far more likely to use doctor's time".

She noted a vicious circle with her patients - they noticed a concerning reading on their watch. They grew concerned. Their pulse rose. They got even more concerned. They re-examined the data, and their reading increased again.

"If we see data about ourselves that we lack context for then, of course, we are going to seek clarification," the psychologist says. "We look, we obsess - it becomes a self-fulfilling prophecy."