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There's a building tension. Visible is the cold breath coming from my rivals as they perform the "pre-race" jiggle on the beginning point.

A rapid twitch of the hips.

I'm participating in my local 5km community parkrun and I'm serious. It's almost time...

Wait a second. I must adjust my tracker. So does the person beside me.

The person waiting expresses impatience. I'm not moving until… yes! Signal acquired, away I go.

Amidst the crowd, it's difficult to see a wrist without a fitness tracker on it. And it's not just us athletes who use them.

This is a booming, massive market. Companies like Samsung Galaxy lead the market, each with an broad range of various versions to cater to a variety of needs. According to how high tech the model you select, price tags can range from an affordable sum to a small fortune.

"It makes me crazy, I can't stop checking."

"It provides solace… It feels like a friend supporting me."

"Please don't notify me I've had a poor sleep."

A handful of the comments people have shared from fellow device users when I inquire what they their opinion is on theirs.

The Monitoring Conundrum

My thoughts on my own device? Currently, annoying. It's reporting I'm not hitting my target, leading me to doubt whether the trees I'm passing under are interfering with my location tracking.

A vast number of us fasten these little devices onto our arms and keep them on 24/7, seemingly at ease with the fact they're continuously tracking us.

Gone are the days when we used them only to give us an idea of our pedometer reading. Today, they can track our sleep quality, heart rate, glucose levels, our VO2 max.

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

But are they able to do what they claim to do? And are the data points we analyse a true reflection of the truth? Do they improve our overall health, or do the avalanche of metrics and cheerleading alerts just increase our sense of overwhelm?

A Complicated Bond

"I find myself getting a quite obsessed with mine," a wearer reveals.

While she appreciates how her device monitors her exercise, she finds some of its other functions "daunting" at times - a feeling that became apparent during a significant period.

Until she found out she could adjust the settings, her smartwatch repeatedly informed her she was not being energetic enough. In a new phase, the watch insists her she's had a poor sleep score.

"I've got a young baby, it's unnecessary for me to be notified I'm tired," she says. "I know that only too well."

Why doesn't she just remove it?

"It's possible, I suppose, but I've got this push-pull dynamic with it," she says. "I love it for its exercise data, I just wonder whether the additional features it can now do is perhaps overkill for me."

How Do They Work?

Every device of smartwatch has its own proprietary way of measuring your bodily functions and interpreting your data, but the vast bulk use sensors on the reverse of the watch.

They typically project small, green LED lights onto your skin which can detect blood flow, identifying your pulse rate. More advanced devices analyse changes in the skin conductance that passes over the skin to get an idea of your stress levels.

The Professional Viewpoint

One expert says that overall for smartwatches, it's a "difficult line" - while the ever-evolving tech could realistically prevent illness, "detecting disease 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 healthy the heart is. They can flag if someone is experiencing atrial fibrillation (AF), where there is erratic electrical activity in the heart causing an irregular heartbeat.

This does not necessarily indicate someone is about to have a heart attack, but it can give an advance notice they might be more at risk of a heart problem in the years to come.

But how to interpret these readings is not straightforward. The expert fears that as additional features are incorporated, people may find it hard to fully understand their data.

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

A clinical psychologist focusing on wearable tech echoes this sentiment. Her work into the effect of wearable tech on a specific group of heart condition patients suggested a noticeable percentage of those who were given devices to monitor their condition experienced greater stress and were "had a higher tendency to use doctor's time".

She noted a cycle with her patients - they saw a concerning reading on their watch. They grew concerned. Their BPM rose. They got more worried. They checked again, and their heart rate increased again.

"When people are presented with data about ourselves that we can't properly interpret then, understandably, we are going to want to know more," the psychologist says. "We check, we obsess - it becomes a vicious cycle."