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A sense of building tension. Visible is the chilled vapour emanating from my rivals as they execute the "pre-race" wiggle on the beginning point.

A rapid movement of the hips.

I'm participating in my local weekly parkrun event and I'm focused. The countdown begins...

Oh, hang on. I need to adjust my watch. As does the guy beside me.

The person waiting sighs. I won't start until… done! Connection established, away I go.

During the scramble, it's hard to find a person without a smartwatch on it. And this isn't only us athletes who wear them.

We're witnessing a booming, massive sector. Names like Garmin lead the market, featuring an wide range of various versions to cater to a range of needs. According to how feature-packed the model you select, costs can start from £100 to a significant investment.

"I find it infuriating, it's impossible to switch off."

"It reassures me… It's like a companion supporting me."

"Stop telling me about a poor sleep."

A small sample of the comments I've had from other tracker enthusiasts when I ask what they think of theirs.

The Data Dilemma

My thoughts on my own device? Right now, irritating. It's telling me I'm not hitting my target, making me wonder whether the foliage along my route are blocking my location tracking.

Millions of us strap these small devices onto our arms and wear them 24/7, seemingly unconcerned with the fact they're constantly tracking us.

Long past are the days when we depended on them exclusively to give us an idea of our daily steps. Today, they can track our sleep patterns, stress levels, oxygen saturation, our VO2 max.

It's a challenge to find a bodily function they fail to monitor.

But do they do what they advertise? And are the numbers we analyse a true reflection of our actual health? Do they improve our daily wellness, or do the avalanche of measurements and motivational messages just contribute to our sense of overwhelm?

A Love-Hate Relationship

"I find myself getting a bit obsessed with mine," one user reveals.

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

Before she realised she could put it into a specific mode, her smartwatch kept telling her she was being insufficiently energetic enough. Now, the watch keeps telling her she's had a bad night's sleep.

"I am caring for a six-month old, there's no point to be told I'm tired," she says. "I know that all too clearly."

Why doesn't she just take it off?

"I could, theoretically, but I have this complicated dynamic with it," she continues. "I appreciate it for its fitness insights, but I'm unsure whether the myriad other functions it can now do is maybe excessive for me."

How Do They Work?

Every device of smartwatch has its own proprietary way of monitoring your health metrics and processing your data, but the majority use optical sensors on the underside of the watch.

They typically emit small, green LED lights onto your skin which can monitor capillary action, identifying your pulse rate. More advanced devices detect changes in the bioimpedance that passes over the skin to gauge your stress levels.

Expert Perspectives

A professor says that for most people for smartwatches, it's a "difficult line" - while the ever-evolving tech could actually prevent illness, "identifying issues before we notice anything", it could also turn us watch wearers into the "concerned but fine".

He points out that some of the latest wearables can carry out tests like heart rhythm analysis, which regularly monitor how healthy the heart is. They can notify if someone is experiencing atrial fibrillation (AF), where there is irregular impulses in the heart causing an irregular heartbeat.

This does not necessarily indicate someone is on the verge of a cardiac event, but it can give an advance notice they might be more vulnerable of a blood clot in the long term.

But how to understand these numbers is complicated. The expert worries that as additional features are added, people may struggle to fully contextualise their data.

"I have some doubts that being able to monitor so many metrics is such a beneficial thing," he says.

A professor studying patient behaviour agrees. Research into the influence of wearable tech on a set of cardiovascular patients suggested a significant portion of those who were given devices to monitor their heart health experienced increased anxiety and were "far more likely to use medical services".

She noted a vicious circle with her patients - they spotted a concerning reading on their watch. They became worried. Their BPM went up. They got even more concerned. They looked a second time, and their heart rate went up again.

"If we see data about ourselves that we can't properly interpret then, of course, we are going to become concerned," the psychologist says. "We look, we obsess - it becomes a self-fulfilling prophecy."