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There's a building tension. I can see the cold breath coming from my rivals as they perform the "about to run" wiggle on the beginning point.

A rapid movement of the hips.

I'm lined up for my local 5km community parkrun and I mean business. It's almost time...

Oh, hang on. I need to sort my tracker. So does the person beside me.

The person in the line sighs. I'm not moving until… there! Signal acquired, and I'm running.

During the scramble, it's difficult to see a wrist without a fitness tracker on it. And this extends beyond us runners who rely on them.

It's a booming, multi-billion pound market. Names like Samsung Galaxy dominate, all offering an extensive selection of different devices to fit a range of lifestyles. Depending on how feature-packed the device you select, costs can range from an affordable sum to a significant investment.

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

"It reassures me… It's like a supporter guiding me."

"Please don't notify me I've had a poor sleep."

Just some of the comments people have shared from other tracker enthusiasts when I question what they their opinion is on theirs.

The Data Dilemma

My thoughts on mine? Currently, irritating. It's reporting I'm not hitting my target, leading me to doubt whether the overhead branches I'm passing under are blocking my location tracking.

Millions of us attach these little gadgets onto our wrists and use them 24/7, ostensibly unconcerned with the fact they're perpetually monitoring us.

A distant memory are the days when we depended on them only to give us an estimation of our daily steps. Now, they can analyse our sleep quality, heart rate, oxygen saturation, our body battery.

It's tricky to find a health indicator they aren't designed to measure.

But do they do what they advertise? And are the statistics we scrutinise a accurate representation of the truth? Do they boost our overall health, or do the avalanche of metrics and cheerleading alerts just contribute to our daily stresses?

A Complicated Bond

"I do get a quite obsessed with mine," one user reveals.

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

Prior to discovering she could put it into a specific mode, her smartwatch kept telling her she was not being energetic enough. In a new phase, the watch insists her she's had a poor sleep score.

"I've got a young baby, it's unnecessary for me to be informed my sleep was poor," she says. "I'm acutely aware only too well."

Couldn't she just take it off?

"I could, perhaps, but I have this complicated dynamic with it," she explains. "I appreciate it for its workout tracking, I just wonder whether the additional features it can now do is maybe overkill for me."

The Technology Behind the Tracking

Different brands of smartwatch has its own novel way of measuring your bodily functions and interpreting your data, but the vast bulk use sensors on the reverse of the watch.

They typically emit small, green LED lights onto your arm which can monitor capillary action, recording your pulse rate. More advanced devices detect changes in the electrical current that passes over the skin to gauge your recovery state.

The Professional Viewpoint

A professor says that overall for smartwatches, it's a "delicate equilibrium" - while the rapidly advancing tech could realistically save lives, "identifying issues before we show symptoms", it could also turn us watch wearers into the "concerned but fine".

He points out that newer wearables can carry out tests like heart rhythm analysis, which regularly monitor how normal the heart is. They can alert if someone is experiencing atrial fibrillation (AF), where there is erratic signals in the heart causing an irregular heartbeat.

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 stroke in the years to come.

But how to interpret these numbers is not straightforward. The expert fears that as more functions are added, people may find it hard to fully comprehend their data.

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

A professor studying patient behaviour concurs. Her work 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 condition experienced greater stress and were "had a higher tendency to use doctor's time".

She identified a vicious circle with her patients - they spotted a alarming metric on their watch. They became worried. Their BPM rose. They got more worried. They checked again, and their heart rate rose further.

"If we see stats about ourselves that we lack context for then, naturally, we are going to become concerned," the psychologist says. "We monitor, we check again - it becomes a self-fulfilling prophecy."