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There's a building tension. I can see the cold breath exhaled by my fellow runners as they do the "starting line" shuffle on the beginning point.

A rapid movement of the hips.

I'm lined up for my local 5km community parkrun and I'm serious. Three, two, one...

Oh, hang on. I need to adjust my watch. So does the person alongside me.

The person behind us sighs. I refuse to go until… yes! Connection established, and I'm running.

In the mele, it's hard to spot a person without a wearable on it. And this isn't only us athletes who wear them.

It's a thriving, multi-billion dollar sector. Brands like Apple Watch dominate, featuring an broad range of various versions to cater to a range of budgets. Depending on how high tech the watch you choose, prices can start from an affordable sum to a significant investment.

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

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

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

A small sample of the responses I've received from like-minded tracker enthusiasts when I ask what they think of theirs.

The Monitoring Conundrum

My current opinion on mine? At this moment, annoying. It's reporting my speed is wrong, making me wonder whether the foliage I'm passing under are disrupting my GPS connection.

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

Gone are the days when we relied on them exclusively to give us an estimation of our daily steps. Currently, they can track our nightly rest, blood pressure, glucose levels, our VO2 max.

It's tricky to find a bodily function they don't track.

But are they able to do what they advertise? And are the numbers we obsess over a faithful picture of reality? Do they boost our daily wellness, or do the multitude of measurements and motivational messages just add to our daily stresses?

Addiction or Aid?

"I do get a quite obsessed with mine," a wearer admits.

While she appreciates how her device tracks her workouts, she finds some of its other capabilities "overwhelming" at times - a feeling initially realised during a major life event.

Before she realised she could put it into a specific mode, her smartwatch kept telling her she was failing to be productive enough. In a new phase, the watch insists her she's had a bad night's sleep.

"I am caring for a infant, it's unnecessary for me to be told I'm tired," she says. "I know that all too clearly."

Why doesn't she just take it off?

"It's possible, perhaps, but I've got this complicated dynamic with it," she continues. "I value it for its workout tracking, I sometimes question whether the additional features it can now do is possibly overkill for me."

Inside the Device

Each model of smartwatch has its own unique way of monitoring your bodily functions and processing your data, but the vast bulk use sensors on the underside of the watch.

They typically project tiny, coloured LED lights onto your skin which can observe capillary action, detecting your heartbeat. Higher-end devices measure changes in the electrical current that passes over the skin to gauge your nervous system activity.

A Fine Balance

A data scientist says that overall for smartwatches, it's a "difficult line" - while the rapidly advancing tech could potentially aid early diagnosis, "detecting disease before we notice anything", it could also turn us device users into the "concerned but fine".

He points out that the most advanced wearables can carry out tests like medical-grade monitoring, which continuously monitor how healthy the heart is. They can alert if someone is experiencing atrial fibrillation (AF), where there is erratic signals in the heart causing an arrhythmia.

This does not automatically signal someone is imminently going to suffer a heart attack, but it can give an advance notice they might be more at risk of a blood clot in the years to come.

But how to interpret these readings is complicated. The expert concerns that as additional features are incorporated, people may struggle to fully comprehend their data.

"I remain sceptical that having the capacity to monitor so many things is such a positive development," he says.

A professor focusing on cardiology agrees. Her work into the impact of wearable tech on a set of cardiovascular patients 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 spotted a concerning reading on their watch. They became worried. Their pulse rose. They got more worried. They checked again, and their heart rate rose further.

"When people are presented with numbers about ourselves that we lack context for then, of course, we are going to want to know more," the psychologist says. "We look, we check again - it becomes a vicious cycle."