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There's a building tension. Apparent is the chilled vapour exhaled by my fellow runners as they do the "about to run" 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 must adjust my watch. As does the guy beside me.

The person waiting expresses impatience. I won't start until… there! Connection established, away I go.

Amidst the crowd, it's challenging to find a wrist without a smartwatch on it. And it's not just us athletes who wear them.

We're witnessing a booming, multi-billion dollar industry. Names like Samsung Galaxy lead the market, all offering an wide range of different devices to suit a variety of needs. Depending on how advanced the watch you go for, price tags can range from an affordable sum to thousands of pounds.

"It makes me crazy, I'm unable to switch off."

"It provides solace… It feels like a supporter encouraging me."

"I wish it wouldn't say I've had a poor sleep."

A small sample of the reactions I've had from other device users when I question what they their opinion is on theirs.

The Data Dilemma

My current opinion on mine? At this moment, frustrating. It's indicating my speed is wrong, leading me to doubt whether the foliage I'm running below are blocking my GPS connection.

Countless individuals of us attach these little gadgets onto our arms and wear them 24/7, ostensibly unconcerned with the fact they're perpetually tracking us.

Gone are the days when we depended on them exclusively to give us an idea of our step count. Now, they can track our sleep quality, stress levels, oxygen saturation, our body battery.

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

But do they do what they say they do? And are the numbers we obsess over a accurate representation of reality? Do they boost our mental and physical wellbeing, or do the avalanche of metrics and cheerleading alerts just contribute to our daily stresses?

Addiction or Aid?

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

While she values how her device records her workouts, she finds some of its other features "daunting" at times - a feeling first discovered during a significant period.

Before she realised she could adjust the settings, her smartwatch constantly alerted her she was not being productive enough. In a new phase, the watch frequently reports her she's had a restless night.

"I've got a young baby, I don't need to be told I've not slept," she says. "I know that perfectly well."

Couldn't she just take it off?

"It's possible, theoretically, but I have this love-hate relationship with it," she continues. "I value it for its workout tracking, I sometimes question whether the additional features it can now do is maybe overkill for me."

How Do They Work?

Each model of smartwatch has its own novel way of monitoring your health metrics and analysing your data, but the majority use sensors on the reverse of the watch.

They commonly shine tiny, coloured LED lights onto your skin which can monitor capillary action, identifying your pulse rate. Higher-end devices measure changes in the skin conductance that passes over the skin to get an idea of your recovery state.

The Professional Viewpoint

A data scientist says that in general for smartwatches, it's a "difficult line" - while the continuously improving tech could potentially save lives, "detecting disease before we notice anything", it could also turn us the tracked into the "anxious healthy".

He points out that the most advanced wearables can conduct tests like electrocardiograms (ECGs), which regularly monitor how normal the heart is. They can alert if someone is experiencing atrial fibrillation (AF), where there is erratic impulses in the heart causing an uneven pulse.

This does not mean 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 readings is complicated. The expert worries that as more functions are introduced, people may find it hard to fully comprehend their data.

"I'm not entirely convinced that the ability to monitor so much data is such a good idea," he says.

A clinical psychologist studying cardiology echoes this sentiment. A study 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 heart health experienced greater stress and were "far more likely to use medical services".

She identified a cycle with her patients - they noticed a worrying figure on their watch. They felt anxious. Their BPM went up. They got more worried. They looked a second time, and their reading increased again.

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