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There's a feeling of anticipation. Visible is the chilled vapour exhaled by my competitors as they execute the "about to run" shuffle on the beginning point.

A swift flick of the hips.

I'm at my local weekly parkrun event and I mean business. The countdown begins...

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

The person in the line tuts. I won't start until… done! Connection established, and I'm running.

Amidst the crowd, it's difficult to find a person without a fitness tracker on it. And this extends beyond us participants who use them.

We're witnessing a thriving, multi-billion pound sector. Names like Garmin dominate, each with an broad range of diverse models to fit a range of budgets. Depending on how high tech the device you go for, costs can range from an affordable sum to thousands of pounds.

"It makes me crazy, I'm unable to relax."

"It reassures me… It feels like a companion guiding me."

"Please don't notify me about a bad night's sleep."

A small sample of the comments I've had from like-minded device users when I inquire what they feel about theirs.

The Monitoring Conundrum

My thoughts on mine? At this moment, annoying. It's indicating my speed is wrong, leading me to doubt whether the trees along my route are interfering with my GPS connection.

Countless individuals of us attach these compact gadgets onto our arms and wear them 24/7, 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 daily steps. Today, they can analyse our sleep patterns, blood pressure, heart rate variability (HRV), our recovery score.

It's difficult to find a bodily function they fail to monitor.

But are they able to do what they advertise? And are the statistics we scrutinise a accurate representation of our actual health? Do they improve our overall health, or do the avalanche of readings and constant notifications just add to our sense of overwhelm?

A Love-Hate Relationship

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

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

Prior to discovering she could adjust the settings, her smartwatch constantly alerted her she was failing to be energetic enough. Now, the watch keeps telling her she's had a restless night.

"I have a six-month old, there's no point to be told my sleep was poor," she says. "I'm acutely aware perfectly well."

Is it not possible to just stop wearing it?

"I could, theoretically, but I've got this love-hate relationship with it," she says. "I love it for its workout tracking, but I'm unsure whether the additional features it can now do is perhaps overkill for me."

How Do They Work?

Each model of smartwatch has its own novel way of measuring your bodily functions and processing your data, but the most use optical sensors on the back of the watch.

They usually project minute LED lights onto your arm which can detect capillary action, recording your heartbeat. More advanced devices analyse changes in the skin conductance that runs through the skin to assess your nervous system activity.

Expert Perspectives

A data scientist says that in general for smartwatches, it's a "difficult line" - while the ever-evolving tech could realistically save lives, "spotting abnormalities before we show symptoms", it could also turn us the tracked into the "concerned but fine".

He points out that some of the latest wearables can perform tests like heart rhythm analysis, which continuously monitor how normal the heart is. They can alert if someone is experiencing an irregular rhythm, where there is abnormal impulses in the heart causing an uneven pulse.

This does not mean someone is about to have a heart attack, but it can give an preliminary indication they might be more at risk of a heart problem in the long term.

But how to understand these readings is not straightforward. The expert fears that as additional features are added, people may struggle to fully comprehend their data.

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

A professor specialising in cardiology concurs. A study into the impact of wearable tech on a cohort of heart condition patients suggested a significant portion of those who were given devices to monitor their heart health experienced increased anxiety and were "far more likely to use healthcare resources".

She observed a vicious circle with her patients - they spotted a alarming metric on their watch. They grew concerned. Their pulse went up. They got even more concerned. They checked again, and their reading rose further.

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