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A sense of nervous excitement. I can see the chilled vapour emanating from my competitors as they perform the "starting line" jiggle on the start line.

A quick flick of the hips.

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

Hold on. I must sort my tracker. So does the guy alongside me.

The person in the line sighs. I refuse to go until… there! Signal acquired, and I'm running.

Amidst the crowd, it's challenging to spot a person without a wearable on it. And this isn't only us participants who rely on them.

It's a explosive, massive sector. Brands like Apple Watch dominate, featuring an extensive selection of various models to suit a spectrum of budgets. Depending on how high tech the model you go for, prices can start from £100 to thousands of pounds.

"It drives me insane, I'm unable to relax."

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

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

A handful of the comments I've received from like-minded tracker enthusiasts when I question what they think of theirs.

The Data Dilemma

My feelings on my own device? Right now, frustrating. It's indicating my speed is wrong, leading me to doubt whether the overhead branches along my route are disrupting my satellite signal.

Countless individuals of us fasten these small gadgets onto our arms and wear them constantly, seemingly comfortable with the fact they're continuously recording us.

A distant memory are the days when we relied on them exclusively to give us an idea of our daily steps. Now, they can measure our sleep quality, stress levels, glucose levels, our VO2 max.

It's difficult to find a physical metric they fail to monitor.

But do they do what they advertise? And are the data points we obsess over a accurate representation of the truth? Do they boost our mental and physical wellbeing, or do the avalanche of measurements and constant notifications just add to our daily stresses?

A Complicated Bond

"I do get a quite fixated with mine," one user confesses.

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

Until she found out she could change its configuration, her smartwatch constantly alerted her she was being insufficiently active enough. Later on, the watch frequently reports her she's had a poor sleep score.

"I have a infant, I don't need to be notified my sleep was poor," she says. "I know that all too clearly."

Couldn't she just remove it?

"I could, perhaps, but I've got this complicated dynamic with it," she explains. "I love it for its fitness insights, I just wonder whether the myriad other functions it can now do is possibly too much for me."

How Do They Work?

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

They commonly project small, green LED lights onto your arm which can observe pulsation, detecting your pulse rate. More advanced devices measure changes in the electrical current that passes over the skin to assess your stress levels.

A Fine Balance

A professor says that in general for smartwatches, it's a "fine balance" - while the rapidly advancing tech could realistically aid early diagnosis, "detecting disease before we feel unwell", it could also turn us the tracked into the "concerned but fine".

He points out that some of the latest wearables can conduct tests like electrocardiograms (ECGs), which constantly monitor how normal the heart is. They can notify if someone is experiencing atrial fibrillation (AF), where there is irregular electrical activity in the heart causing an uneven pulse.

This does not mean someone is on the verge of a heart attack, but it can give an early warning they might be more susceptible of a heart problem in the future.

But how to interpret these readings is complicated. The expert worries that as more functions are incorporated, people may not be able to fully comprehend their data.

"I have some doubts that the ability to monitor so much data is such a positive development," he says.

A professor studying patient behaviour agrees. Her work into the influence of wearable tech on a cohort of individuals with health issues suggested a minority of those who were given devices to monitor their heart health experienced heightened worry and were "far more likely to use doctor's time".

She identified a pattern with her patients - they spotted a worrying figure on their watch. They grew concerned. Their pulse rose. They got increasingly anxious. They looked a second time, and their reading rose further.

"Upon viewing data about ourselves that we can't properly interpret then, of course, we are going to seek clarification," the psychologist says. "We monitor, we obsess - it becomes a feedback loop."