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An atmosphere of nervous excitement. Visible is the chilled vapour coming from my fellow runners as they perform the "starting line" jiggle on the starting line.

A swift flick of the hips.

I'm at my local 5km community parkrun and I mean business. Three, two, one...

Wait a second. I must start my tracker. As does the person beside me.

The person waiting tuts. I'm not moving until… yes! GPS ready, away I go.

In the mele, it's challenging to see a person without a smartwatch on it. And this extends beyond us athletes who use them.

This is a booming, massive industry. Brands like Apple Watch lead the market, each with an extensive array of different devices to fit a spectrum of budgets. Based on how feature-packed the watch you choose, costs can start from an affordable sum to thousands of pounds.

"I find it infuriating, I'm unable to stop checking."

"It reassures me… It acts as a friend supporting me."

"Stop telling me I've had a bad night's sleep."

Just some of the comments I've had from other tracker enthusiasts when I ask what they their opinion is on theirs.

A Sea of Statistics

My current opinion on mine? At this moment, irritating. It's reporting I'm off pace, causing me to question whether the overhead branches I'm running below are blocking my GPS connection.

Countless individuals of us attach these compact monitors onto our arms and use them constantly, seemingly unconcerned with the fact they're perpetually recording us.

Gone are the days when we used them solely to give us an estimation of our daily steps. Now, they can analyse our nightly rest, heart rate, oxygen saturation, our VO2 max.

It's a challenge to find a bodily function they aren't designed to measure.

But do they do what they claim to do? And are the data points we obsess over a accurate representation of the truth? Do they improve our daily wellness, or do the multitude of measurements and cheerleading alerts just contribute to our everyday anxiety?

A Love-Hate Relationship

"I do get a bit fixated with mine," one user confesses.

While she loves how her device records her exercise, she finds some of its other functions "excessive" at times - a feeling first discovered during a major life event.

Until she found out she could put it into a specific mode, her smartwatch repeatedly informed her she was being insufficiently productive enough. In a new phase, the watch keeps telling her she's had a poor sleep score.

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

Couldn't she just remove it?

"I could, theoretically, but I've got this complicated dynamic with it," she says. "I appreciate it for its workout tracking, I just wonder whether the additional features it can now do is maybe 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 most use optical sensors on the back of the watch.

They usually project tiny, coloured LED lights onto your skin which can monitor blood flow, recording your BPM. Sophisticated devices detect changes in the bioimpedance that runs through the skin to get an idea of your stress levels.

Expert Perspectives

A data scientist says that for most people for smartwatches, it's a "delicate equilibrium" - while the continuously improving tech could realistically prevent illness, "identifying issues before we show symptoms", it could also turn us device users into the "concerned but fine".

He points out that the most advanced wearables can perform tests like medical-grade monitoring, which regularly monitor how stable the heart is. They can flag if someone is experiencing an irregular rhythm, where there is irregular signals in the heart causing an uneven pulse.

This does not necessarily indicate someone is on the verge of a cardiac event, but it can give an advance notice they might be more at risk of a heart problem in the years to come.

But how to make sense of these numbers is not straightforward. The expert concerns that as further capabilities are added, people may struggle to fully comprehend their data.

"I remain sceptical that the ability to monitor so much data is such a beneficial thing," he says.

A professor studying cardiology agrees. A study into the impact of wearable tech on a specific group of cardiovascular 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 doctor's time".

She observed a cycle with her patients - they spotted a alarming metric on their watch. They became worried. Their pulse increased. They got more worried. They re-examined the data, and their heart rate rose further.

"Upon viewing numbers about ourselves that we can't properly interpret then, understandably, we are going to become concerned," the psychologist says. "We monitor, we check again - it becomes a self-fulfilling prophecy."