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An atmosphere of feeling of anticipation. I can see the cold breath exhaled by my fellow runners as they do the "about to run" shuffle on the beginning point.

A quick flick of the hips.

I'm lined up for my local Saturday morning race and I'm focused. Three, two, one...

Oh, hang on. I have to sort my watch. The same goes for the guy beside me.

The person in the line tuts. I refuse to go until… done! Connection established, away I go.

During the scramble, it's challenging to see a arm without a fitness tracker on it. And it's not just us runners who use them.

We're witnessing a explosive, massive market. Companies like Samsung Galaxy dominate, each with an extensive array of different devices to fit a spectrum of needs. According to how feature-packed the watch you choose, prices can vary between £100 to a small fortune.

"I find it infuriating, I can't switch off."

"It comforts me… It's like a supporter guiding me."

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

Just some of the reactions I've had from fellow device users when I inquire what they think of theirs.

The Data Dilemma

My thoughts on mine? Right now, frustrating. It's indicating my speed is wrong, making me wonder whether the foliage I'm running below are blocking my location tracking.

Countless individuals of us fasten these small devices onto our wrists and use them all day and night, ostensibly comfortable with the fact they're perpetually monitoring us.

Gone are the days when we used them only to give us an rough count of our pedometer reading. Today, they can track our nightly rest, heart rate, glucose levels, our VO2 max.

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

But can they do what they advertise? And are the data points we obsess over a faithful picture of our actual health? Do they enhance our mental and physical wellbeing, or do the plethora of readings and constant notifications just contribute to our everyday anxiety?

A Love-Hate Relationship

"I find myself getting a bit obsessed with mine," one user admits.

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

Prior to discovering she could change its configuration, her smartwatch constantly alerted her she was being insufficiently active enough. In a new phase, the watch insists her she's had a poor sleep score.

"I have a infant, it's unnecessary for me to be told I'm tired," she says. "I know that only too well."

Couldn't she just take it off?

"I could, perhaps, but I've got this love-hate relationship with it," she explains. "I love it for its exercise data, I sometimes question whether the additional features it can now do is perhaps too much for me."

Inside the Device

Each model of smartwatch has its own proprietary way of measuring your health metrics and interpreting your data, but the vast bulk use sensors on the back of the watch.

They commonly shine tiny, coloured LED lights onto your arm which can observe blood flow, identifying your heartbeat. More advanced devices measure changes in the electrical current that runs through the skin to gauge your nervous system activity.

The Professional Viewpoint

A professor says that in general for smartwatches, it's a "delicate equilibrium" - while the rapidly advancing tech could actually aid early diagnosis, "identifying issues before we feel unwell", it could also turn us device users into the "worried well".

He points out that the most advanced wearables can conduct tests like medical-grade monitoring, which constantly monitor how normal the heart is. They can notify if someone is experiencing a heart arrhythmia, where there is abnormal signals in the heart causing an irregular heartbeat.

This does not necessarily indicate someone is about to have a heart attack, but it can give an early warning they might be more susceptible of a stroke in the long term.

But how to interpret these readings is complicated. The expert worries that as further capabilities are introduced, people may find it hard to fully understand their data.

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

A health researcher studying wearable tech agrees. Her work into the impact of wearable tech on a cohort of cardiovascular patients suggested a minority of those who were given devices to monitor their cardiac function experienced increased anxiety and were "had a higher tendency to use medical services".

She observed a cycle with her patients - they saw a alarming metric on their watch. They became worried. Their pulse increased. They got increasingly anxious. They checked again, and their anxiety increased again.

"When people are presented with data about ourselves that we can't properly interpret then, naturally, we are going to want to know more," the psychologist says. "We look, we check again - it becomes a self-fulfilling prophecy."