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There's a nervous excitement. Apparent is the cold breath coming from my competitors as they execute the "pre-race" jiggle on the beginning point.

A rapid flick of the hips.

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

Hold on. I have to start my tracker. As does the runner alongside me.

The person behind us expresses impatience. I won't start until… done! GPS ready, away I go.

During the scramble, it's difficult to see a wrist without a wearable on it. And this extends beyond us athletes who rely on them.

It's a explosive, multi-billion pound market. Brands like Apple Watch lead the market, each with an broad selection of various models to fit a spectrum of budgets. Depending on how high tech the device you go for, price tags can vary between an affordable sum to thousands of pounds.

"It drives me insane, I can't relax."

"It provides solace… It's like a friend supporting me."

"Please don't notify me about a restless night."

A handful of the responses I've received from other tracker enthusiasts when I inquire what they their opinion is on theirs.

The Data Dilemma

My thoughts on my own device? Currently, irritating. It's indicating I'm not hitting my target, leading me to doubt whether the overhead branches I'm passing under are interfering with my satellite signal.

Millions of us strap these small monitors onto our wrists and use them constantly, apparently at ease with the fact they're continuously recording us.

A distant memory are the days when we used them only to give us an estimation of our pedometer reading. Currently, they can measure our sleep patterns, stress levels, heart rate variability (HRV), our recovery score.

It's difficult to find a physical metric they aren't designed to measure.

But do they do what they say they do? And are the statistics we scrutinise a accurate representation of reality? Do they boost our daily wellness, or do the multitude of readings and cheerleading alerts just add to our daily stresses?

Addiction or Aid?

"I do get a bit obsessed with mine," one user admits.

While she appreciates how her device monitors her runs, she finds some of its other capabilities "overwhelming" at times - a feeling first discovered during a significant period.

Until she found out she could put it into a specific mode, her smartwatch constantly alerted her she was failing to be productive enough. Later on, the watch keeps telling her she's had a poor sleep score.

"I have a infant, there's no point to be told I've not slept," she says. "That fact is all too clearly."

Couldn't she just take it off?

"It's possible, I suppose, but I've got this push-pull dynamic with it," she says. "I value it for its exercise data, but I'm unsure whether the additional features it can now do is possibly too much for me."

How Do They Work?

Different brands of smartwatch has its own proprietary way of monitoring your health metrics and interpreting your data, but the most use optical sensors on the reverse of the watch.

They commonly shine tiny, coloured LED lights onto your wrist which can observe blood flow, identifying your heartbeat. Higher-end devices measure changes in the bioimpedance that runs through the skin to assess your stress levels.

A Fine Balance

A data scientist says that in general for smartwatches, it's a "fine balance" - while the rapidly advancing tech could actually aid early diagnosis, "spotting abnormalities before we show symptoms", it could also turn us device users into the "anxious healthy".

He points out that some of the latest wearables can conduct tests like electrocardiograms (ECGs), which constantly monitor how normal the heart is. They can notify if someone is experiencing a heart arrhythmia, where there is irregular electrical activity in the heart causing an uneven pulse.

This does not necessarily indicate someone is on the verge of a cardiac event, but it can give an early warning they might be more at risk of a blood clot in the long term.

But how to interpret these numbers is complicated. The expert fears that as further capabilities are introduced, people may find it hard 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 clinical psychologist studying patient behaviour echoes this sentiment. Research into the effect of wearable tech on a specific group of individuals with health issues suggested a significant portion of those who were given devices to monitor their condition experienced greater stress and were "more inclined to use doctor's time".

She identified a pattern with her patients - they saw a concerning reading on their watch. They felt anxious. Their pulse rose. They got even more concerned. They checked again, and their anxiety went up again.

"Upon viewing stats about ourselves that we lack context for then, of course, we are going to become concerned," the psychologist says. "We monitor, we re-check - it becomes a vicious cycle."