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There's a nervous excitement. Visible is the frosty air exhaled by my rivals as they do the "starting line" wiggle on the beginning point.

A quick flick of the hips.

I'm lined up for my local weekly parkrun event and I'm focused. Three, two, one...

Oh, hang on. I must adjust my watch. So does the runner beside me.

The person in the line expresses impatience. I'm not moving until… done! Connection established, and I'm running.

Amidst the crowd, it's hard to see a arm without a wearable on it. And this isn't only us participants who wear them.

It's a thriving, multi-billion dollar industry. Names like Apple Watch dominate, all offering an broad range of different devices to suit a spectrum of lifestyles. Based on how advanced the watch you go for, prices can vary between a hundred pounds to a small fortune.

"It makes me crazy, I can't switch off."

"It comforts me… It acts as a friend supporting me."

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

A small sample of the comments I've had from like-minded smartwatch wearers when I question what they think of theirs.

The Data Dilemma

My thoughts on mine? At this moment, annoying. It's telling me my speed is wrong, making me wonder whether the trees along my route are interfering with my satellite signal.

Millions of us fasten these compact monitors onto our wrists and keep them on all day and night, seemingly at ease with the fact they're perpetually monitoring us.

Long past are the days when we used them exclusively to give us an rough count of our step count. Now, they can track our sleep patterns, heart rate, heart rate variability (HRV), our VO2 max.

It's tricky to find a health indicator they aren't designed to measure.

But can they do what they claim to do? And are the numbers we analyse a faithful picture of the truth? Do they improve our daily wellness, or do the avalanche of measurements and motivational messages just add to our sense of overwhelm?

Addiction or Aid?

"I find myself getting a bit obsessed with mine," one user reveals.

While she loves how her device records her exercise, she finds some of its other functions "daunting" at times - a feeling initially realised during a significant period.

Before she realised she could adjust the settings, her smartwatch constantly alerted her she was failing to be active enough. Later on, the watch insists her she's had a bad night's sleep.

"I've got a young baby, I don't need to be told I'm tired," she says. "I'm acutely aware perfectly well."

Is it not possible to just remove it?

"I could, theoretically, but I have this love-hate relationship with it," she explains. "I love it for its workout tracking, I sometimes question whether the myriad other functions it can now do is perhaps too much for me."

The Technology Behind the Tracking

Each model of smartwatch has its own novel way of monitoring your vitals and analysing your data, but the most use optical sensors on the underside of the watch.

They usually emit tiny, coloured LED lights onto your skin which can detect pulsation, detecting your BPM. Sophisticated devices analyse changes in the bioimpedance that flows through the skin to get an idea of your nervous system activity.

The Professional Viewpoint

One expert says that in general for smartwatches, it's a "delicate equilibrium" - while the ever-evolving tech could actually aid early diagnosis, "identifying issues before we notice anything", it could also turn us the tracked into the "worried well".

He points out that newer wearables can carry out tests like electrocardiograms (ECGs), which regularly monitor how stable the heart is. They can alert if someone is experiencing an irregular rhythm, where there is irregular electrical activity in the heart causing an irregular heartbeat.

This does not mean someone is about to have a heart attack, but it can give an advance notice they might be more susceptible of a stroke in the years to come.

But how to make sense of these numbers is complex. The expert concerns that as further capabilities are incorporated, people may find it hard to fully contextualise their data.

"I have some doubts that the ability to monitor so much data is such a positive development," he says.

A clinical psychologist specialising in cardiology agrees. Research into the influence of wearable tech on a set of individuals with health issues 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 identified a cycle with her patients - they saw a worrying figure on their watch. They became worried. Their heart rate increased. They got increasingly anxious. They checked again, and their heart rate increased again.

"If we see numbers about ourselves that we don't really understand then, understandably, we are going to seek clarification," the psychologist says. "We monitor, we re-check - it becomes a feedback loop."