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A sense of nervous excitement. I can see the cold breath emanating from my rivals as they perform the "pre-race" jiggle on the start line.

A rapid flick of the hips.

I'm participating in my local Saturday morning race and I'm serious. The countdown begins...

Hold on. I must start my watch. So does the guy beside me.

The person in the line sighs. I won't start until… yes! Signal acquired, and I'm running.

In the mele, it's hard to spot a wrist without a smartwatch on it. And it's not just us athletes who wear them.

It's a booming, massive industry. Names like Garmin lead the market, all offering an extensive range of various models to fit a variety of lifestyles. Depending on how advanced the watch you go for, prices can range from an affordable sum to a significant investment.

"It makes me crazy, it's impossible to switch off."

"It comforts me… It acts as a supporter supporting me."

"I wish it wouldn't say I've experienced a bad night's sleep."

A handful of the reactions I've had from fellow device users when I inquire what they think of theirs.

The Data Dilemma

My current opinion on my own device? At this moment, irritating. It's telling me I'm off pace, causing me to question whether the trees along my route are disrupting my satellite signal.

Millions of us fasten these little monitors onto our wrists and keep them on constantly, apparently at ease with the fact they're continuously recording us.

A distant memory are the days when we used them solely to give us an estimation of our pedometer reading. Today, they can track our sleep quality, blood pressure, glucose levels, our body battery.

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

But are they able to do what they claim to do? And are the statistics we scrutinise a faithful picture of the truth? Do they boost our overall health, or do the avalanche of metrics and cheerleading alerts just increase our everyday anxiety?

A Love-Hate Relationship

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

While she loves how her device tracks her runs, she finds some of its other features "daunting" at times - a feeling that became apparent during a pregnancy.

Before she realised she could put it into a specific mode, her smartwatch repeatedly informed her she was being insufficiently active enough. In a new phase, the watch insists her she's had a bad night's sleep.

"I've got a infant, it's unnecessary for me to be notified my sleep was poor," she says. "I know that only too well."

Why doesn't she just take it off?

"I suppose I could, I suppose, but I'm in this push-pull dynamic with it," she says. "I love it for its fitness insights, I just wonder whether the myriad other functions it can now do is maybe excessive for me."

Inside the Device

Every device of smartwatch has its own unique way of measuring your bodily functions and processing your data, but the vast bulk use optical sensors on the reverse of the watch.

They typically shine tiny, coloured LED lights onto your wrist which can detect pulsation, recording your pulse rate. Higher-end devices analyse changes in the skin conductance that passes over the skin to get an idea of your stress levels.

A Fine Balance

A data scientist says that overall for smartwatches, it's a "fine balance" - while the continuously improving tech could realistically aid early diagnosis, "identifying issues before we notice anything", it could also turn us device users into the "worried well".

He points out that some of the latest wearables can conduct tests like electrocardiograms (ECGs), which constantly monitor how stable the heart is. They can flag if someone is experiencing an irregular rhythm, where there is irregular impulses in the heart causing an irregular heartbeat.

This does not automatically signal someone is about to have a cardiac event, but it can give an early warning they might be more susceptible of a blood clot in the years to come.

But how to understand these readings is not straightforward. The expert worries that as more functions are introduced, people may not be able to fully comprehend their data.

"I'm not entirely convinced that having the capacity to monitor so many metrics is such a good idea," he says.

A clinical psychologist focusing on cardiology echoes this sentiment. A study into the effect of wearable tech on a cohort of individuals with health issues suggested a minority of those who were given devices to monitor their heart health experienced greater stress and were "had a higher tendency to use healthcare resources".

She identified a pattern with her patients - they noticed a worrying figure on their watch. They became worried. Their BPM increased. They got more worried. They looked a second time, and their heart rate increased again.

"When people are presented with data about ourselves that we lack context for then, of course, we are going to become concerned," the psychologist says. "We look, we obsess - it becomes a self-fulfilling prophecy."