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There's a building tension. I can see the frosty air exhaled by my rivals as they do the "pre-race" shuffle on the starting line.

A quick movement of the hips.

I'm lined up for my local Saturday morning race and I mean business. Three, two, one...

Wait a second. I have to sort my device. As does the person next to me.

The person waiting expresses impatience. I won't start until… done! Connection established, I'm off.

In the mele, it's hard to find a person without a smartwatch on it. And this isn't only us participants who use them.

It's a booming, multi-billion pound market. Brands like Apple Watch are prevalent, featuring an extensive range of diverse models to cater to a spectrum of budgets. Depending on how advanced the model you go for, prices can vary between a hundred pounds to a small fortune.

"It drives me insane, I can't relax."

"It comforts me… It feels like a friend supporting me."

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

A small sample of the reactions I've had from like-minded tracker enthusiasts when I ask what they their opinion is on theirs.

A Sea of Statistics

My thoughts on mine? Right now, irritating. It's reporting my speed is wrong, causing me to question whether the overhead branches I'm running below are disrupting my location tracking.

Countless individuals of us fasten these compact gadgets onto our arms and wear them all day and night, apparently comfortable with the fact they're constantly recording us.

Gone are the days when we depended on them only to give us an rough count of our pedometer reading. Currently, they can measure our sleep quality, blood pressure, heart rate variability (HRV), our VO2 max.

It's difficult to find a physical metric they don't track.

But are they able to do what they advertise? And are the statistics we scrutinise a faithful picture of reality? Do they enhance our mental and physical wellbeing, or do the plethora of measurements and motivational messages just increase our sense of overwhelm?

A Complicated Bond

"I do get a a little preoccupied with mine," an individual confesses.

While she values how her device records her runs, she finds some of its other functions "overwhelming" at times - a feeling initially realised during a pregnancy.

Prior to discovering she could put it into a specific mode, her smartwatch repeatedly informed her she was failing to be energetic enough. Now, the watch frequently reports her she's had a poor sleep score.

"I've got a six-month old, it's unnecessary for me to be told my sleep was poor," she says. "I know that all too clearly."

Is it not possible to just stop wearing it?

"I suppose I could, theoretically, but I've got this love-hate relationship with it," she says. "I value it for its exercise data, I just wonder whether the additional features it can now do is maybe overkill for me."

The Technology Behind the Tracking

Each model of smartwatch has its own proprietary way of tracking your health metrics and processing your data, but the most use optical sensors on the underside of the watch.

They usually project minute LED lights onto your skin which can detect blood flow, identifying your pulse rate. More advanced devices measure changes in the bioimpedance that passes over the skin to get an idea of your stress levels.

The Professional Viewpoint

A data scientist says that for most people for smartwatches, it's a "fine balance" - while the continuously improving tech could realistically save lives, "detecting disease before we show symptoms", it could also turn us device users into the "worried well".

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

This does not mean someone is on the verge of a heart attack, but it can give an advance notice they might be more at risk of a blood clot in the future.

But how to understand these figures is complex. The expert fears that as additional features are introduced, people may struggle to fully comprehend their data.

"I remain sceptical that the ability to monitor so much data is such a positive development," he says.

A professor studying patient behaviour echoes this sentiment. Her work into the impact of wearable tech on a set of cardiovascular patients suggested a minority of those who were given devices to monitor their heart health experienced increased anxiety and were "had a higher tendency to use healthcare resources".

She identified a vicious circle with her patients - they spotted a alarming metric on their watch. They felt anxious. Their pulse went up. They got even more concerned. They looked a second time, and their reading increased again.

"Upon viewing stats about ourselves that we lack context for then, understandably, we are going to become concerned," the psychologist says. "We monitor, we re-check - it becomes a vicious cycle."