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A sense of building tension. I can see the cold breath coming from my competitors as they do the "about to run" shuffle on the starting line.

A quick twitch of the hips.

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

Wait a second. I need to start my device. As does the guy alongside me.

The person behind us expresses impatience. I won't start until… yes! Connection established, I'm off.

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

We're witnessing a booming, multi-billion dollar sector. Names like Samsung Galaxy dominate, each with an broad range of different devices to suit a range of budgets. Based on how feature-packed the device you select, prices can start from £100 to thousands of pounds.

"It makes me crazy, I'm unable to stop checking."

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

"Stop telling me I've had a poor sleep."

A handful of the responses I've received from other tracker enthusiasts when I inquire what they think of theirs.

The Data Dilemma

My feelings on my own device? At this moment, irritating. It's reporting I'm off pace, leading me to doubt whether the trees I'm passing under are interfering with my satellite signal.

Millions of us fasten these small devices onto our arms and keep them on 24/7, ostensibly at ease with the fact they're continuously recording us.

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

It's a challenge to find a health indicator they fail to monitor.

But do they do what they say they do? And are the statistics we obsess over a accurate representation of the truth? Do they boost our overall health, or do the multitude of readings and cheerleading alerts just increase our daily stresses?

Addiction or Aid?

"I find myself getting a bit preoccupied with mine," an individual reveals.

While she appreciates how her device records her exercise, she finds some of its other functions "excessive" at times - a feeling initially realised during a pregnancy.

Until she found out she could change its configuration, her smartwatch kept telling her she was not being energetic enough. Now, the watch keeps telling her she's had a bad night's sleep.

"I am caring for a six-month old, I don't need to be notified I'm tired," she says. "That fact is only too well."

Couldn't she just take it off?

"It's possible, I suppose, but I'm in this push-pull dynamic with it," she explains. "I appreciate it for its workout tracking, I sometimes question whether the additional features it can now do is perhaps overkill for me."

Inside the Device

Different brands of smartwatch has its own unique way of monitoring your vitals and processing your data, but the most use optical sensors 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 detect changes in the bioimpedance that passes over the skin to gauge your recovery state.

The Professional Viewpoint

One expert says that overall for smartwatches, it's a "delicate equilibrium" - while the ever-evolving tech could potentially prevent illness, "detecting disease before we show symptoms", it could also turn us watch wearers into the "concerned but fine".

He points out that the most advanced wearables can conduct tests like electrocardiograms (ECGs), which continuously monitor how normal the heart is. They can flag if someone is experiencing a heart arrhythmia, where there is erratic signals in the heart causing an arrhythmia.

This does not automatically signal someone is about to have a cardiac event, but it can give an advance notice they might be more vulnerable of a heart problem in the long term.

But how to make sense of these numbers is not straightforward. The expert fears that as more functions are introduced, people may struggle to fully understand their data.

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

A professor specialising in wearable tech agrees. A study into the impact of wearable tech on a cohort of cardiovascular patients suggested a minority of those who were given devices to monitor their heart health experienced greater stress and were "more inclined to use healthcare resources".

She observed a cycle with her patients - they spotted a worrying figure on their watch. They felt anxious. Their heart rate rose. They got increasingly anxious. They re-examined the data, and their anxiety increased again.

"Upon viewing stats about ourselves that we lack context for then, understandably, we are going to want to know more," the psychologist says. "We monitor, we obsess - it becomes a self-fulfilling prophecy."