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There's a feeling of anticipation. I can see the cold breath coming from my fellow runners as they do the "starting line" shuffle on the start line.

A rapid movement of the hips.

I'm lined up for my local weekly parkrun event and I'm focused. The countdown begins...

Oh, hang on. I must start my tracker. The same goes for the runner alongside me.

The person in the line expresses impatience. I refuse to go until… yes! GPS ready, and I'm running.

In the mele, it's challenging to see a wrist without a wearable on it. And this isn't only us runners who rely on them.

This is a explosive, multi-billion dollar market. Brands like Apple Watch lead the market, featuring an wide range of diverse versions to cater to a range of needs. Depending on how feature-packed the device you go for, costs can start from a hundred pounds to a significant investment.

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

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

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

Just some of the reactions I've received from fellow tracker enthusiasts when I inquire what they think of theirs.

A Sea of Statistics

My thoughts on my own device? Currently, annoying. It's telling me my speed is wrong, making me wonder whether the trees along my route are disrupting my location tracking.

Countless individuals of us strap these compact devices onto our arms and wear them constantly, ostensibly unconcerned with the fact they're continuously monitoring us.

Long past are the days when we relied on them exclusively to give us an rough count of our step count. Currently, they can analyse our nightly rest, blood pressure, heart rate variability (HRV), our VO2 max.

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

But do they do what they claim to do? And are the numbers we obsess over a true reflection of the truth? Do they boost our overall health, or do the multitude of metrics and constant notifications just contribute to our daily stresses?

Addiction or Aid?

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

While she values how her device tracks her exercise, she finds some of its other functions "daunting" at times - a feeling that became apparent during a significant period.

Prior to discovering she could change its configuration, her smartwatch kept telling her she was failing to be productive 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 informed I'm tired," she says. "That fact is only too well."

Couldn't she just stop wearing it?

"It's possible, theoretically, but I'm in this push-pull dynamic with it," she continues. "I appreciate it for its fitness insights, I sometimes question whether the additional features it can now do is maybe excessive for me."

The Technology Behind the Tracking

Every device of smartwatch has its own proprietary way of monitoring your health metrics and interpreting your data, but the vast bulk use sensors on the underside of the watch.

They usually project minute LED lights onto your wrist which can detect capillary action, identifying your BPM. Sophisticated devices detect changes in the skin conductance that passes over the skin to gauge your stress levels.

A Fine Balance

A data scientist says that in general for smartwatches, it's a "fine balance" - while the ever-evolving tech could actually prevent illness, "spotting abnormalities before we feel unwell", it could also turn us the tracked into the "worried well".

He points out that some of the latest wearables can carry out tests like medical-grade monitoring, which constantly 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 about to have a cardiac event, but it can give an preliminary indication they might be more at risk of a blood clot in the long term.

But how to understand these numbers is complex. The expert worries that as more functions are added, people may struggle to fully contextualise their data.

"I'm not entirely convinced that the ability to monitor so many metrics is such a beneficial thing," he says.

A health researcher studying cardiology agrees. Research into the influence of wearable tech on a cohort of heart condition patients suggested a noticeable percentage of those who were given devices to monitor their condition experienced greater stress and were "had a higher tendency to use healthcare resources".

She noted a pattern with her patients - they saw a worrying figure on their watch. They felt anxious. Their heart rate rose. They got increasingly anxious. They re-examined the data, and their heart rate went up again.

"If we see stats about ourselves that we can't properly interpret then, understandably, we are going to seek clarification," the psychologist says. "We check, we obsess - it becomes a vicious cycle."