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There's a building tension. Visible is the chilled vapour exhaled by my competitors as they perform the "about to run" shuffle on the start line.

A rapid movement of the hips.

I'm lined up for my local 5km community parkrun and I'm focused. The countdown begins...

Hold on. I need to start my watch. So does the guy beside me.

The person waiting tuts. I refuse to go until… done! Connection established, and I'm running.

During the scramble, it's hard to spot a wrist without a wearable on it. And it's not just us runners who wear them.

We're witnessing a thriving, massive sector. Names like Samsung Galaxy dominate, featuring an extensive range of various versions to cater to a spectrum of needs. Based on how feature-packed the device you choose, price tags can range from a hundred pounds to thousands of pounds.

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

"It provides solace… It's like a companion supporting me."

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

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

The Monitoring Conundrum

My feelings on my own device? At this moment, annoying. It's indicating I'm off pace, causing me to question whether the foliage I'm passing under are disrupting my location tracking.

A vast number of us strap these compact gadgets onto our arms and keep them on constantly, seemingly at ease with the fact they're constantly tracking us.

Long past are the days when we relied on them only to give us an rough count of our step count. Today, they can analyse our nightly rest, stress levels, heart rate variability (HRV), our body battery.

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

But do they do what they say they do? And are the numbers we analyse a accurate representation of our actual health? Do they improve our overall health, or do the multitude of readings and motivational messages just contribute to our daily stresses?

Addiction or Aid?

"I become a bit obsessed with mine," an individual admits.

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

Prior to discovering she could change its configuration, her smartwatch constantly alerted her she was not being productive enough. In a new phase, the watch insists her she's had a restless night.

"I've got a infant, I don't need to be told I've not slept," she says. "I'm acutely aware perfectly well."

Is it not possible to just remove it?

"I suppose I could, perhaps, but I'm in this love-hate relationship with it," she says. "I appreciate it for its fitness insights, I sometimes question whether all the other things it can now do is maybe too much for me."

How Do They Work?

Different brands of smartwatch has its own novel way of measuring your bodily functions and analysing your data, but the most use sensors on the underside of the watch.

They usually shine minute LED lights onto your skin which can monitor blood flow, recording your pulse rate. Higher-end devices measure changes in the electrical current that passes over the skin to gauge your stress levels.

Expert Perspectives

A data scientist says that for most people for smartwatches, it's a "fine balance" - while the rapidly advancing tech could realistically aid early diagnosis, "spotting abnormalities before we feel unwell", it could also turn us the tracked into the "concerned but fine".

He points out that the most advanced wearables can carry out tests like electrocardiograms (ECGs), which regularly monitor how healthy the heart is. They can notify if someone is experiencing atrial fibrillation (AF), where there is erratic signals in the heart causing an uneven pulse.

This does not automatically signal someone is imminently going to suffer a heart attack, but it can give an early warning they might be more susceptible of a heart problem in the years to come.

But how to make sense of these readings is not straightforward. The expert concerns that as additional features are added, people may not be able to fully contextualise their data.

"I remain sceptical that the ability to monitor so many things is such a beneficial thing," he says.

A clinical psychologist specialising in cardiology agrees. Research into the influence of wearable tech on a set of heart condition patients suggested a minority of those who were given devices to monitor their cardiac function experienced heightened worry and were "had a higher tendency to use medical services".

She identified a cycle with her patients - they saw a concerning reading on their watch. They felt anxious. Their BPM went up. They got even more concerned. They looked a second time, and their heart rate increased again.

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