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There's a feeling of anticipation. I can see the chilled vapour exhaled by my competitors as they perform the "pre-race" jiggle on the beginning point.

A quick flick of the hips.

I'm at my local 5km community parkrun and I'm serious. The countdown begins...

Wait a second. I must start my watch. So does the person beside 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 spot a person without a wearable on it. And this isn't only us runners who rely on them.

This is a thriving, multi-billion pound market. Companies like Samsung Galaxy lead the market, each with an wide selection of diverse versions to suit a spectrum of budgets. Based on how advanced the device you select, costs can range from an affordable sum to thousands of pounds.

"It drives me insane, I can't stop checking."

"It provides solace… It's like a friend guiding me."

"Stop telling me I've experienced a poor sleep."

A small sample of the responses I've received from like-minded smartwatch wearers when I ask what they think of theirs.

A Sea of Statistics

My thoughts on mine? At this moment, irritating. It's indicating my speed is wrong, causing me to question whether the trees I'm running below are interfering with my location tracking.

Millions of us fasten these small devices onto our wrists and wear them constantly, apparently at ease with the fact they're continuously tracking us.

Long past are the days when we used them only to give us an estimation of our pedometer reading. Today, they can track our sleep patterns, blood pressure, glucose levels, our body battery.

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

But do they do what they advertise? And are the data points we analyse a faithful picture of the truth? Do they improve our daily wellness, or do the multitude of readings and cheerleading alerts just increase our sense of overwhelm?

Addiction or Aid?

"I do get a a little obsessed with mine," one user confesses.

While she appreciates how her device records her exercise, she finds some of its other capabilities "excessive" at times - a feeling initially realised during a pregnancy.

Before she realised she could adjust the settings, her smartwatch constantly alerted her she was failing to be energetic enough. In a new phase, the watch insists her she's had a poor sleep score.

"I've got a six-month old, I don't need to be informed I'm tired," she says. "I'm acutely aware all too clearly."

Is it not possible to just stop wearing it?

"It's possible, I suppose, but I've got this push-pull dynamic with it," she says. "I value it for its workout tracking, but I'm unsure whether the myriad other functions it can now do is maybe overkill for me."

How Do They Work?

Different brands of smartwatch has its own novel way of monitoring your vitals and analysing your data, but the vast bulk use detectors on the reverse of the watch.

They typically emit small, green LED lights onto your wrist which can observe blood flow, recording your heartbeat. More advanced devices measure changes in the electrical current that flows through the skin to assess your recovery state.

The Professional Viewpoint

One expert says that overall for smartwatches, it's a "difficult line" - while the rapidly advancing tech could potentially aid early diagnosis, "detecting disease before we notice anything", it could also turn us the tracked into the "concerned but fine".

He points out that the most advanced wearables can perform tests like heart rhythm analysis, which continuously monitor how stable the heart is. They can alert if someone is experiencing an irregular rhythm, where there is irregular electrical activity in the heart causing an uneven pulse.

This does not automatically signal someone is about to have a heart attack, but it can give an early warning they might be more susceptible of a blood clot in the future.

But how to make sense of these figures is complicated. The expert worries that as additional features are added, people may find it hard to fully comprehend their data.

"I remain sceptical that having the capacity to monitor so many metrics is such a beneficial thing," he says.

A clinical psychologist studying patient behaviour agrees. A study into the influence of wearable tech on a set 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 doctor's time".

She observed a pattern with her patients - they saw a worrying figure on their watch. They became worried. Their heart rate went up. They got even more concerned. They looked a second time, and their reading went up again.

"When people are presented with data about ourselves that we don't really understand then, naturally, we are going to seek clarification," the psychologist says. "We check, we re-check - it becomes a self-fulfilling prophecy."