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There's a nervous excitement. Visible is the frosty air emanating from my rivals as they do the "starting line" jiggle on the beginning point.

A swift movement of the hips.

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

Oh, hang on. I need to adjust my device. The same goes for the person alongside me.

The person waiting sighs. I won't start until… done! GPS ready, I'm off.

In the mele, it's hard to find a wrist without a fitness tracker on it. And it's not just us participants who rely on them.

It's a thriving, multi-billion dollar market. Companies like Samsung Galaxy are prevalent, featuring an extensive selection of different devices to suit a spectrum of needs. Based on how high tech the watch you go for, prices can start from £100 to a small fortune.

"It drives me insane, it's impossible to relax."

"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 received from like-minded tracker enthusiasts when I inquire what they think of theirs.

The Data Dilemma

My thoughts on mine? Currently, frustrating. It's reporting I'm not hitting my target, making me wonder whether the foliage along my route are blocking my GPS connection.

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

Gone are the days when we relied on them only to give us an idea of our daily steps. Now, they can track our sleep patterns, blood pressure, glucose levels, 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 numbers we analyse a accurate representation of reality? Do they boost our overall health, or do the avalanche of metrics and cheerleading alerts just contribute to our sense of overwhelm?

A Complicated Bond

"I find myself getting a quite obsessed with mine," an individual confesses.

While she appreciates how her device monitors her workouts, she finds some of its other capabilities "daunting" at times - a feeling initially realised during a significant period.

Until she found out she could put it into a specific mode, her smartwatch repeatedly informed her she was failing to be energetic enough. Now, the watch frequently reports her she's had a poor sleep score.

"I have a six-month old, there's no point to be notified I've not slept," she says. "I know that perfectly well."

Couldn't she just stop wearing it?

"I suppose I could, theoretically, but I have this complicated dynamic with it," she continues. "I love it for its workout tracking, I just wonder whether the additional features it can now do is maybe overkill for me."

How Do They Work?

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

They commonly 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 assess your stress levels.

Expert Perspectives

A professor says that in general for smartwatches, it's a "fine balance" - while the ever-evolving tech could actually aid early diagnosis, "spotting abnormalities before we show symptoms", it could also turn us device users into the "concerned but fine".

He points out that newer wearables can carry out tests like medical-grade monitoring, which constantly monitor how stable the heart is. They can notify if someone is experiencing an irregular rhythm, where there is abnormal signals in the heart causing an uneven pulse.

This does not mean someone is about to have a cardiac event, but it can give an preliminary indication they might be more vulnerable of a stroke in the years to come.

But how to interpret these numbers is complex. The expert fears that as further capabilities are incorporated, people may struggle to fully contextualise their data.

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

A clinical psychologist specialising in cardiology concurs. Her work into the impact of wearable tech on a cohort of heart condition patients suggested a noticeable percentage of those who were given devices to monitor their cardiac function experienced increased anxiety and were "had a higher tendency to use healthcare resources".

She identified a cycle with her patients - they saw a alarming metric on their watch. They felt anxious. Their pulse rose. They got even more concerned. They re-examined the data, and their reading increased again.

"If we see numbers about ourselves that we lack context for then, naturally, we are going to want to know more," the psychologist says. "We look, we re-check - it becomes a self-fulfilling prophecy."