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There's a feeling of anticipation. I can see the cold breath emanating from my fellow runners as they perform the "about to run" jiggle on the beginning point.

A swift flick of the hips.

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

Hold on. I have to sort my tracker. The same goes for the runner next to me.

The person behind us sighs. I refuse to go until… yes! Connection established, I'm off.

In the mele, it's difficult to find a person without a smartwatch on it. And it's not just us athletes who rely on them.

It's a thriving, multi-billion pound sector. Brands like Samsung Galaxy lead the market, each with an broad range of different devices to fit a range of needs. According to how high tech the watch you go for, costs can vary between an affordable sum to thousands of pounds.

"It drives me insane, it's impossible to stop checking."

"It provides solace… It feels like a companion encouraging me."

"Stop telling me I've had a restless night."

A handful of the comments I've received from like-minded tracker enthusiasts when I ask what they their opinion is on theirs.

The Monitoring Conundrum

My current opinion on mine? At this moment, irritating. It's reporting I'm off pace, leading me to doubt whether the trees I'm passing under are interfering with my GPS connection.

Millions of us attach these little monitors onto our arms and wear them all day and night, ostensibly unconcerned with the fact they're perpetually tracking us.

Long past are the days when we relied on them exclusively to give us an estimation of our step count. Now, they can track our sleep quality, stress levels, oxygen saturation, our recovery score.

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 obsess over a accurate representation of our actual health? Do they improve our overall health, or do the plethora of readings and cheerleading alerts just contribute to our daily stresses?

Addiction or Aid?

"I do get a bit fixated with mine," a wearer reveals.

While she values how her device monitors her exercise, she finds some of its other features "excessive" at times - a feeling that became apparent during a pregnancy.

Until she found out she could put it into a specific mode, her smartwatch kept telling her she was failing to be active enough. Later on, the watch insists her she's had a bad night's sleep.

"I am caring for a six-month old, there's no point to be informed I'm tired," she says. "That fact is all too clearly."

Why doesn't she just stop wearing it?

"I could, perhaps, but I have this love-hate relationship with it," she explains. "I love it for its fitness insights, I just wonder whether the myriad other functions it can now do is maybe too much for me."

How Do They Work?

Every device of smartwatch has its own novel way of monitoring your bodily functions and interpreting your data, but the vast bulk use optical sensors on the reverse of the watch.

They usually shine tiny, coloured LED lights onto your arm which can observe capillary action, detecting your BPM. More advanced devices measure changes in the bioimpedance that runs through the skin to get an idea of your recovery state.

A Fine Balance

A data scientist says that for most people for smartwatches, it's a "delicate equilibrium" - while the continuously improving tech could realistically prevent illness, "spotting abnormalities before we notice anything", it could also turn us the tracked into the "worried well".

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

This does not mean someone is imminently going to suffer a heart attack, but it can give an advance notice they might be more at risk of a stroke in the years to come.

But how to interpret these figures is complicated. The expert concerns that as more functions are added, people may find it hard to fully understand their data.

"I remain sceptical that having the capacity to monitor so many things is such a good idea," he says.

A health researcher focusing on patient behaviour agrees. Research into the effect of wearable tech on a cohort of heart condition patients suggested a significant portion of those who were given devices to monitor their cardiac function experienced increased anxiety and were "more inclined to use healthcare resources".

She identified a vicious circle with her patients - they spotted a worrying figure on their watch. They felt anxious. Their heart rate increased. They got more worried. They checked again, and their anxiety rose further.

"If we see data about ourselves that we lack context for then, naturally, we are going to become concerned," the psychologist says. "We look, we re-check - it becomes a feedback loop."