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There's a building tension. Apparent is the frosty air coming from my rivals as they perform the "pre-race" jiggle on the start line.

A swift flick of the hips.

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

Oh, hang on. I must sort my watch. The same goes for the person next to me.

The person waiting expresses impatience. I'm not moving until… there! GPS ready, I'm off.

Amidst the crowd, it's difficult to find a arm without a wearable on it. And this extends beyond us runners who wear them.

We're witnessing a booming, multi-billion dollar industry. Names like Garmin are prevalent, all offering an wide selection of diverse versions to fit a spectrum of budgets. Based on how feature-packed the model you go for, price tags can vary between an affordable sum to a small fortune.

"It makes me crazy, it's impossible to switch off."

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

"Stop telling me I've experienced a restless night."

A handful of the responses I've had from fellow tracker enthusiasts when I ask what they their opinion is on theirs.

The Monitoring Conundrum

My current opinion on mine? Right now, frustrating. It's indicating I'm off pace, leading me to doubt whether the trees I'm running below are blocking my satellite signal.

Countless individuals of us attach these small monitors onto our arms and use them constantly, ostensibly at ease with the fact they're perpetually monitoring us.

Long past are the days when we relied on them only to give us an estimation of our daily steps. Currently, they can track our nightly rest, heart rate, oxygen saturation, our recovery score.

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

But can they do what they advertise? And are the data points we scrutinise a accurate representation of reality? Do they enhance our overall health, or do the plethora of metrics and motivational messages just contribute to our daily stresses?

Addiction or Aid?

"I do get a bit obsessed with mine," a wearer reveals.

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

Until she found out she could adjust the settings, her smartwatch kept telling her she was failing to be energetic enough. In a new phase, the watch keeps telling her she's had a restless night.

"I am caring for a six-month old, there's no point to be told I've not slept," she says. "That fact is all too clearly."

Couldn't she just remove it?

"I could, perhaps, but I've got this complicated dynamic with it," she continues. "I love it for its exercise data, but I'm unsure whether all the other things it can now do is perhaps overkill for me."

How Do They Work?

Every device of smartwatch has its own unique way of tracking your bodily functions and interpreting your data, but the most use detectors on the underside of the watch.

They usually project minute LED lights onto your arm which can observe blood flow, recording your BPM. Sophisticated devices measure changes in the skin conductance that runs through the skin to get an idea of your recovery state.

A Fine Balance

A data scientist says that for most people for smartwatches, it's a "delicate equilibrium" - while the ever-evolving tech could potentially 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 stable the heart is. They can alert if someone is experiencing an irregular rhythm, where there is erratic signals in the heart causing an irregular heartbeat.

This does not automatically signal someone is about to have a heart attack, but it can give an early warning they might be more susceptible of a blood clot in the years to come.

But how to interpret these figures is complex. The expert worries that as further capabilities are added, people may not be able to fully understand their data.

"I'm not entirely convinced that having the capacity to monitor so many metrics is such a positive development," he says.

A professor studying patient behaviour concurs. Her work into the impact of wearable tech on a cohort of cardiovascular 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 noted a vicious circle with her patients - they spotted a concerning reading on their watch. They became worried. Their BPM increased. They got even more concerned. They re-examined the data, and their reading rose further.

"When people are presented with stats about ourselves that we don't really understand then, of course, we are going to become concerned," the psychologist says. "We look, we obsess - it becomes a self-fulfilling prophecy."