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There's a nervous excitement. Visible is the chilled vapour exhaled by my fellow runners as they perform the "about to run" shuffle on the starting line.

A swift twitch of the hips.

I'm lined up for my local 5km community parkrun and I mean business. The countdown begins...

Wait a second. I have to adjust my device. So does the guy beside me.

The person waiting expresses impatience. I refuse to go until… yes! GPS ready, I'm off.

Amidst the crowd, it's hard to see a wrist without a wearable on it. And this isn't only us runners who rely on them.

This is a explosive, massive sector. Brands like Samsung Galaxy are prevalent, featuring an broad range of various devices to suit a spectrum of lifestyles. Based on how feature-packed the model you select, costs can range from a hundred pounds to thousands of pounds.

"I find it infuriating, I can't switch off."

"It comforts me… It feels like a companion encouraging me."

"Please don't notify me I've had a restless night."

Just some of the responses people have shared from fellow tracker enthusiasts when I ask what they think of theirs.

A Sea of Statistics

My feelings on mine? At this moment, frustrating. It's telling me I'm not hitting my target, causing me to question whether the foliage along my route are interfering with my GPS connection.

A vast number of us strap these little monitors onto our arms and wear them all day and night, ostensibly comfortable with the fact they're continuously recording us.

Gone are the days when we used them solely to give us an estimation of our daily steps. Currently, they can track our sleep quality, blood pressure, oxygen saturation, our VO2 max.

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

But can they do what they advertise? And are the numbers we scrutinise a accurate representation of our actual health? Do they boost our mental and physical wellbeing, or do the multitude of measurements and cheerleading alerts just increase our everyday anxiety?

A Complicated Bond

"I become a bit fixated with mine," an individual confesses.

While she values how her device monitors her exercise, she finds some of its other capabilities "overwhelming" at times - a feeling initially realised during a pregnancy.

Prior to discovering she could adjust the settings, her smartwatch constantly alerted her she was failing to be energetic enough. Now, the watch insists her she's had a poor sleep score.

"I have a infant, I don't need to be told my sleep was poor," she says. "I'm acutely aware perfectly well."

Why doesn't she just stop wearing it?

"I could, theoretically, but I have this complicated dynamic with it," she says. "I value it for its workout tracking, I sometimes question whether the myriad other functions it can now do is possibly excessive for me."

Inside the Device

Different brands of smartwatch has its own novel way of tracking your bodily functions and processing your data, but the majority use sensors on the reverse of the watch.

They typically project minute LED lights onto your arm which can detect pulsation, recording your heartbeat. Sophisticated devices analyse changes in the skin conductance that passes over the skin to get an idea of your stress levels.

Expert Perspectives

One expert says that in general for smartwatches, it's a "fine balance" - while the continuously improving tech could realistically aid early diagnosis, "spotting abnormalities before we feel unwell", it could also turn us device users into the "worried well".

He points out that some of the latest wearables can conduct tests like medical-grade monitoring, which constantly monitor how normal the heart is. They can notify if someone is experiencing a heart arrhythmia, where there is abnormal electrical activity in the heart causing an uneven pulse.

This does not necessarily indicate someone is imminently going to suffer a heart attack, but it can give an preliminary indication they might be more vulnerable of a heart problem in the years to come.

But how to understand these readings is complicated. The expert fears that as more functions are added, people may not be able to fully understand their data.

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

A health researcher studying cardiology agrees. Her work into the impact of wearable tech on a set of heart condition patients suggested a significant portion of those who were given devices to monitor their condition experienced increased anxiety and were "more inclined to use medical services".

She identified a pattern with her patients - they spotted a worrying figure on their watch. They felt anxious. Their heart rate rose. They got even more concerned. They re-examined the data, and their heart rate rose further.

"When people are presented with stats about ourselves that we can't properly interpret then, understandably, we are going to become concerned," the psychologist says. "We monitor, we obsess - it becomes a self-fulfilling prophecy."