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An atmosphere of building tension. I can see the frosty air emanating from my fellow runners as they do the "pre-race" wiggle on the beginning point.

A swift flick of the hips.

I'm participating in my local 5km community parkrun and I mean business. It's almost time...

Oh, hang on. I have to adjust my watch. So does the guy beside me.

The person behind us tuts. I refuse to go until… yes! Signal acquired, away I go.

In the mele, it's challenging to see a person without a wearable on it. And it's not just us athletes who wear them.

It's a booming, multi-billion pound sector. Names like Apple Watch lead the market, all offering an broad range of different versions to fit a range of budgets. According to how high tech the watch you go for, price tags can range from a hundred pounds to a small fortune.

"I find it infuriating, I can't switch off."

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

"I wish it wouldn't say I've experienced a poor sleep."

A handful of the responses I've had from fellow device users when I inquire what they feel about theirs.

A Sea of Statistics

My feelings on mine? Right now, annoying. It's telling me my speed is wrong, making me wonder whether the foliage along my route are disrupting my satellite signal.

Countless individuals of us attach these small gadgets onto our arms and use them all day and night, apparently comfortable with the fact they're constantly monitoring us.

Gone are the days when we relied on them exclusively to give us an idea of our daily steps. Now, they can track our nightly rest, blood pressure, heart rate variability (HRV), our recovery score.

It's difficult to find a health indicator they fail to monitor.

But are they able to do what they say they do? And are the statistics we scrutinise a faithful picture of our actual health? Do they improve our overall health, or do the multitude of readings and constant notifications just increase our everyday anxiety?

Addiction or Aid?

"I find myself getting a quite preoccupied with mine," a wearer confesses.

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

Until she found out she could put it into a specific mode, her smartwatch kept telling her she was failing to be productive enough. In a new phase, the watch keeps telling her she's had a restless night.

"I am caring for a young baby, I don't need to be informed I'm tired," she says. "I know that all too clearly."

Is it not possible to just remove it?

"I suppose I could, perhaps, but I have this love-hate relationship with it," she continues. "I appreciate it for its fitness insights, but I'm unsure whether the myriad other functions it can now do is perhaps overkill for me."

How Do They Work?

Every device of smartwatch has its own novel way of tracking your health metrics and analysing your data, but the vast bulk use detectors on the back of the watch.

They usually shine small, green LED lights onto your wrist which can observe capillary action, identifying your BPM. Higher-end devices analyse changes in the skin conductance that flows through the skin to get an idea of your recovery state.

Expert Perspectives

One expert says that for most people for smartwatches, it's a "difficult line" - while the continuously improving tech could potentially prevent illness, "detecting disease before we notice anything", it could also turn us device users into the "anxious healthy".

He points out that newer wearables can conduct tests like electrocardiograms (ECGs), which constantly monitor how stable the heart is. They can alert if someone is experiencing atrial fibrillation (AF), where there is irregular signals in the heart causing an arrhythmia.

This does not mean someone is about to have a cardiac event, but it can give an advance notice they might be more susceptible of a heart problem in the future.

But how to interpret these figures is not straightforward. The expert worries that as further capabilities are incorporated, people may struggle to fully contextualise their data.

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

A health researcher studying patient behaviour agrees. A study into the influence of wearable tech on a set of cardiovascular patients suggested a noticeable percentage of those who were given devices to monitor their condition experienced heightened worry and were "had a higher tendency to use healthcare resources".

She identified a cycle with her patients - they spotted a concerning reading on their watch. They grew concerned. Their heart rate went up. They got more worried. They re-examined the data, and their anxiety increased again.

"Upon viewing stats about ourselves that we don't really understand then, understandably, we are going to want to know more," the psychologist says. "We look, we re-check - it becomes a vicious cycle."