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An atmosphere of nervous excitement. Visible is the cold breath emanating from my fellow runners as they perform the "pre-race" wiggle on the beginning point.

A quick flick of the hips.

I'm participating in my local weekly parkrun event and I'm serious. It's almost time...

Wait a second. I need to adjust my tracker. So does the guy alongside me.

The person behind us tuts. I'm not moving until… done! GPS ready, I'm off.

During the scramble, it's challenging to see a person without a wearable on it. And this extends beyond us participants who wear them.

This is a thriving, multi-billion dollar sector. Brands like Apple Watch are prevalent, featuring an wide range of different models to fit a range of budgets. According to how advanced the device you go for, costs can start from £100 to thousands of pounds.

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

"It reassures me… It's like a supporter encouraging me."

"I wish it wouldn't say I've had a restless night."

A handful of the comments I've had from other device users when I ask what they feel about theirs.

A Sea of Statistics

My feelings on my own device? At this moment, irritating. It's indicating my speed is wrong, leading me to doubt whether the trees I'm running below are interfering with my satellite signal.

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

Gone are the days when we used them exclusively to give us an estimation of our daily steps. Today, they can analyse our nightly rest, stress levels, oxygen saturation, our body battery.

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

But are they able to do what they say they do? And are the statistics we scrutinise a faithful picture of the truth? Do they improve our daily wellness, or do the plethora of readings and cheerleading alerts just add to our daily stresses?

A Love-Hate Relationship

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

While she loves how her device tracks her runs, she finds some of its other features "overwhelming" at times - a feeling initially realised during a pregnancy.

Until she found out she could adjust the settings, her smartwatch constantly alerted her she was being insufficiently active enough. Now, the watch insists her she's had a bad night's sleep.

"I have a infant, I don't need to be told I'm tired," she says. "I know that all too clearly."

Is it not possible to just take it off?

"I could, I suppose, but I've got this love-hate relationship with it," she says. "I appreciate it for its exercise data, I just wonder whether all the other things it can now do is maybe excessive for me."

How Do They Work?

Each model of smartwatch has its own proprietary way of tracking your bodily functions and processing your data, but the most use detectors on the underside of the watch.

They usually shine minute LED lights onto your skin which can observe blood flow, identifying your heartbeat. More advanced devices analyse changes in the bioimpedance that runs through the skin to get an idea of your stress levels.

Expert Perspectives

One expert says that for most people for smartwatches, it's a "fine balance" - while the continuously improving tech could realistically save lives, "identifying issues before we feel unwell", 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 heart rhythm analysis, which continuously monitor how stable the heart is. They can alert if someone is experiencing a heart arrhythmia, where there is abnormal impulses in the heart causing an uneven pulse.

This does not necessarily indicate someone is imminently going to suffer a heart attack, but it can give an early warning they might be more vulnerable of a blood clot in the long term.

But how to understand these readings is complex. The expert fears that as additional features are added, people may find it hard to fully understand their data.

"I'm not entirely convinced that being able to monitor so many metrics is such a positive development," he says.

A professor focusing on wearable tech echoes this sentiment. A study into the impact of wearable tech on a specific group of heart condition patients suggested a significant portion of those who were given devices to monitor their heart health experienced increased anxiety and were "had a higher tendency to use healthcare resources".

She identified a vicious circle with her patients - they noticed a concerning reading on their watch. They became worried. Their pulse rose. They got more worried. They looked a second time, and their reading went up again.

"Upon viewing stats about ourselves that we lack context for then, of course, we are going to become concerned," the psychologist says. "We monitor, we check again - it becomes a self-fulfilling prophecy."