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There's a nervous excitement. I can see the frosty air emanating from my rivals as they do the "about to run" jiggle on the starting line.

A swift flick of the hips.

I'm at my local Saturday morning race and I'm focused. It's almost time...

Oh, hang on. I must start my device. As does the runner alongside me.

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

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

It's a explosive, massive market. Brands like Samsung Galaxy dominate, all offering an extensive selection of different versions to suit a variety of lifestyles. Depending on how advanced the watch you choose, price tags can start from a hundred pounds to a small fortune.

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

"It provides solace… It's like a friend encouraging me."

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

Just some of the comments people have shared from like-minded tracker enthusiasts when I ask what they think of theirs.

A Sea of Statistics

My thoughts on my own device? At this moment, irritating. It's indicating my speed is wrong, making me wonder whether the foliage I'm passing under are blocking my GPS connection.

Millions of us fasten these compact devices onto our arms and keep them on all day and night, ostensibly comfortable with the fact they're continuously recording us.

Long past are the days when we depended on them solely to give us an idea of our daily steps. Currently, they can analyse our sleep patterns, heart rate, glucose levels, our body battery.

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

But do they do what they advertise? And are the numbers we obsess over a faithful picture of our actual health? Do they improve our daily wellness, or do the multitude of metrics and motivational messages just contribute to our everyday anxiety?

Addiction or Aid?

"I do get a a little obsessed with mine," a wearer confesses.

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

Before she realised she could adjust the settings, her smartwatch kept telling her she was not being energetic enough. Now, the watch keeps telling her she's had a poor sleep score.

"I've got a six-month old, there's no point to be notified I'm tired," she says. "I know that all too clearly."

Couldn't she just stop wearing it?

"I could, theoretically, but I have this love-hate relationship with it," she says. "I appreciate it for its exercise data, I sometimes question whether the myriad other functions it can now do is possibly excessive 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 optical sensors on the back of the watch.

They commonly project minute LED lights onto your arm which can detect blood flow, identifying your heartbeat. Sophisticated devices detect changes in the skin conductance that runs through the skin to gauge your nervous system activity.

A Fine Balance

A professor says that for most people for smartwatches, it's a "difficult line" - while the rapidly advancing tech could realistically aid early diagnosis, "spotting abnormalities before we notice anything", it could also turn us watch wearers into the "worried well".

He points out that some of the latest wearables can carry out tests like electrocardiograms (ECGs), which continuously monitor how normal the heart is. They can alert if someone is experiencing an irregular rhythm, where there is erratic signals in the heart causing an irregular heartbeat.

This does not mean someone is on the verge of a cardiac event, but it can give an early warning they might be more at risk of a stroke in the years to come.

But how to make sense of these readings is complex. The expert fears that as additional features are incorporated, people may find it hard to fully contextualise their data.

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

A health researcher studying wearable tech echoes this sentiment. Research into the impact of wearable tech on a set of individuals with health issues suggested a noticeable percentage of those who were given devices to monitor their condition experienced greater stress and were "far more likely to use doctor's time".

She observed a vicious circle with her patients - they spotted a concerning reading on their watch. They grew concerned. Their heart rate went up. They got even more concerned. They checked again, and their reading rose further.

"If we see 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 re-check - it becomes a self-fulfilling prophecy."