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

A rapid flick of the hips.

I'm lined up for my local 5km community parkrun and I'm focused. It's almost time...

Wait a second. I must sort my tracker. So does the runner alongside me.

The person waiting sighs. I won't start until… there! GPS ready, away I go.

In the mele, it's difficult to see a arm without a fitness tracker on it. And this isn't only us participants who wear them.

We're witnessing a thriving, multi-billion dollar industry. Names like Samsung Galaxy are prevalent, featuring an extensive array of different models to cater to a range of needs. According to how high tech the device you choose, price tags can vary between £100 to a small fortune.

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

"It comforts me… It feels like a friend supporting me."

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

Just some of the comments people have shared from like-minded device users when I inquire what they their opinion is on theirs.

A Sea of Statistics

My current opinion on my own device? At this moment, annoying. It's indicating I'm not hitting my target, causing me to question whether the trees I'm passing under are interfering with my location tracking.

A vast number of us fasten these small devices onto our wrists and use them all day and night, apparently comfortable with the fact they're perpetually tracking us.

A distant memory are the days when we used them exclusively to give us an rough count of our step count. Now, they can track our nightly rest, blood pressure, glucose levels, our VO2 max.

It's a challenge to find a health indicator they aren't designed to measure.

But can they do what they claim to do? And are the statistics we scrutinise a accurate representation of our actual health? Do they improve our overall health, or do the avalanche of metrics and constant notifications just contribute to our sense of overwhelm?

Addiction or Aid?

"I find myself getting a bit obsessed with mine," an individual confesses.

While she values how her device records her runs, she finds some of its other functions "overwhelming" at times - a feeling that became apparent during a pregnancy.

Prior to discovering she could change its configuration, her smartwatch kept telling her she was failing to be productive enough. In a new phase, the watch keeps telling her she's had a bad night's sleep.

"I have a young baby, it's unnecessary for me to be told I've not slept," she says. "I'm acutely aware only too well."

Is it not possible to just remove it?

"It's possible, perhaps, but I have this push-pull dynamic with it," she explains. "I value it for its workout tracking, I just wonder whether all the other things it can now do is perhaps too much for me."

How Do They Work?

Every device of smartwatch has its own proprietary way of tracking your vitals and analysing your data, but the most use sensors on the underside of the watch.

They usually shine small, green LED lights onto your skin which can observe capillary action, detecting your pulse rate. Higher-end devices measure changes in the bioimpedance that flows through the skin to get an idea of your nervous system activity.

A Fine Balance

A professor says that overall for smartwatches, it's a "delicate equilibrium" - while the ever-evolving tech could potentially aid early diagnosis, "detecting disease 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 perform tests like medical-grade monitoring, which regularly monitor how stable the heart is. They can notify if someone is experiencing atrial fibrillation (AF), where there is erratic electrical activity in the heart causing an arrhythmia.

This does not mean someone is imminently going to suffer a cardiac event, but it can give an preliminary indication they might be more vulnerable of a stroke in the long term.

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

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

A professor focusing on 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 cardiac function experienced increased anxiety and were "more inclined to use medical services".

She noted a pattern with her patients - they noticed a alarming metric on their watch. They felt anxious. Their pulse increased. They got more worried. They looked a second time, and their anxiety went up again.

"Upon viewing stats about ourselves that we don't really understand then, of course, we are going to become concerned," the psychologist says. "We look, we re-check - it becomes a self-fulfilling prophecy."