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There's a nervous excitement. Apparent is the chilled vapour coming from my fellow runners as they perform the "pre-race" wiggle on the beginning point.

A rapid movement of the hips.

I'm lined up for my local weekly parkrun event and I'm serious. It's almost time...

Oh, hang on. I must start my tracker. So does the runner next to me.

The person in the line tuts. I'm not moving until… done! GPS ready, I'm off.

During the scramble, it's challenging to spot a wrist without a wearable on it. And this isn't only us participants who wear them.

This is a booming, multi-billion dollar market. Names like Garmin are prevalent, each with an broad array of diverse devices to suit a variety of lifestyles. Based on how advanced the watch you choose, costs can range from £100 to a significant investment.

"I find it infuriating, I can't switch off."

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

"I wish it wouldn't say about a poor sleep."

A small sample of the reactions I've had from other device users when I question what they feel about theirs.

The Monitoring Conundrum

My thoughts on my own device? Currently, irritating. It's indicating I'm not hitting my target, making me wonder whether the overhead branches I'm running below are interfering with my location tracking.

Millions of us fasten these compact devices onto our arms and use them all day and night, apparently at ease with the fact they're constantly monitoring us.

Gone are the days when we used them only to give us an rough count of our daily steps. Currently, they can track our sleep patterns, heart rate, heart rate variability (HRV), our recovery score.

It's tricky to find a physical metric they don't track.

But do they do what they claim to do? And are the statistics we scrutinise a faithful picture of reality? Do they improve our mental and physical wellbeing, or do the multitude of measurements and constant notifications just contribute to our everyday anxiety?

A Love-Hate Relationship

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

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

Before she realised she could adjust the settings, her smartwatch kept telling her she was being insufficiently energetic enough. Later on, the watch frequently reports her she's had a poor sleep score.

"I am caring for a six-month old, it's unnecessary for me to be notified I've not slept," she says. "That fact is perfectly well."

Why doesn't she just take it off?

"I suppose I could, perhaps, but I'm in this love-hate relationship with it," she says. "I love it for its workout tracking, I just wonder whether the additional features it can now do is maybe overkill for me."

The Technology Behind the Tracking

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

They commonly project small, green LED lights onto your skin which can observe blood flow, identifying your heartbeat. Higher-end devices analyse changes in the skin conductance that passes over the skin to gauge your stress levels.

The Professional Viewpoint

One expert says that overall for smartwatches, it's a "difficult line" - while the rapidly advancing tech could realistically save lives, "spotting abnormalities before we notice anything", it could also turn us watch wearers into the "concerned but fine".

He points out that newer wearables can carry out tests like electrocardiograms (ECGs), which continuously monitor how normal the heart is. They can notify if someone is experiencing an irregular rhythm, where there is erratic impulses in the heart causing an irregular heartbeat.

This does not necessarily indicate someone is imminently going to suffer a heart attack, but it can give an advance notice they might be more susceptible of a heart problem in the years to come.

But how to understand these figures is not straightforward. The expert fears that as more functions are introduced, people may not be able to fully understand their data.

"I have some doubts that having the capacity to monitor so many metrics is such a good idea," he says.

A health researcher specialising in wearable tech agrees. Her work into the effect of wearable tech on a specific group of heart condition patients suggested a significant portion of those who were given devices to monitor their condition experienced heightened worry and were "had a higher tendency to use healthcare resources".

She identified a pattern with her patients - they saw a worrying figure on their watch. They grew concerned. Their pulse increased. They got even more concerned. They re-examined the data, and their reading went up again.

"When people are presented with numbers about ourselves that we can't properly interpret then, naturally, we are going to become concerned," the psychologist says. "We check, we obsess - it becomes a vicious cycle."