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An atmosphere of building tension. Apparent is the chilled vapour exhaled by my competitors as they do the "starting line" jiggle on the start line.

A quick flick of the hips.

I'm participating in my local weekly parkrun event and I mean business. Three, two, one...

Wait a second. I need to sort my tracker. The same goes for the runner next to me.

The person in the line expresses impatience. I won't start until… there! Connection established, I'm off.

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

We're witnessing a thriving, multi-billion dollar market. Companies like Garmin dominate, featuring an extensive range of diverse devices to fit a range of lifestyles. Based on how high tech the watch you choose, costs can range from £100 to thousands of pounds.

"It drives me insane, I'm unable to switch off."

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

"Stop telling me about a bad night's sleep."

A handful of the comments I've received from other smartwatch wearers when I question what they their opinion is on theirs.

A Sea of Statistics

My thoughts on mine? Right now, frustrating. It's telling me I'm not hitting my target, causing me to question whether the foliage I'm running below are disrupting my location tracking.

Millions of us attach these little gadgets onto our wrists and wear them 24/7, seemingly at ease with the fact they're continuously recording us.

Gone are the days when we depended on them only to give us an rough count of our pedometer reading. Today, they can measure our nightly rest, stress levels, oxygen saturation, our VO2 max.

It's difficult to find a physical metric they aren't designed to measure.

But are they able to do what they advertise? And are the statistics we analyse a faithful picture of reality? Do they improve our daily wellness, or do the avalanche of measurements and constant notifications just add to our sense of overwhelm?

A Love-Hate Relationship

"I do get a a little fixated with mine," a wearer reveals.

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

Until she found out she could adjust the settings, her smartwatch kept telling her she was being insufficiently productive enough. Later on, the watch frequently reports her she's had a poor sleep score.

"I am caring for a six-month old, I don't need to be notified I'm tired," she says. "I know that all too clearly."

Is it not possible to just take it off?

"It's possible, theoretically, but I have this push-pull dynamic with it," she says. "I love it for its workout tracking, I sometimes question whether the additional features it can now do is perhaps overkill for me."

How Do They Work?

Different brands of smartwatch has its own proprietary way of monitoring your vitals and processing your data, but the vast bulk use detectors on the reverse of the watch.

They typically project small, green LED lights onto your skin which can observe blood flow, detecting your pulse rate. More advanced devices detect changes in the bioimpedance that flows through the skin to assess your nervous system activity.

The Professional Viewpoint

A professor says that for most people for smartwatches, it's a "delicate equilibrium" - while the rapidly advancing tech could realistically aid early diagnosis, "spotting abnormalities before we feel unwell", it could also turn us device users into the "anxious healthy".

He points out that some of the latest wearables can carry out tests like heart rhythm analysis, which constantly monitor how healthy the heart is. They can flag if someone is experiencing a heart arrhythmia, where there is irregular impulses in the heart causing an arrhythmia.

This does not necessarily indicate someone is about to have a cardiac event, but it can give an preliminary indication they might be more vulnerable of a blood clot in the long term.

But how to make sense of these figures is not straightforward. The expert worries that as additional features are added, people may find it hard to fully understand their data.

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

A health researcher specialising in wearable tech echoes this sentiment. Her work into the effect of wearable tech on a set of individuals with health issues suggested a noticeable percentage of those who were given devices to monitor their cardiac function experienced increased anxiety and were "had a higher tendency to use doctor's time".

She observed a pattern with her patients - they spotted a alarming metric on their watch. They felt anxious. Their pulse rose. They got more worried. They re-examined the data, and their reading rose further.

"When people are presented with numbers about ourselves that we can't properly interpret then, understandably, we are going to want to know more," the psychologist says. "We check, we check again - it becomes a feedback loop."