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An atmosphere of feeling of anticipation. Apparent is the frosty air emanating from my fellow runners as they perform the "starting line" jiggle on the start line.

A swift flick of the hips.

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

Hold on. I need to sort my watch. The same goes for the person beside me.

The person waiting tuts. I won't start until… done! GPS ready, I'm off.

Amidst the crowd, it's challenging to spot a wrist without a fitness tracker on it. And this isn't only us runners who use them.

This is a thriving, multi-billion dollar market. Brands like Samsung Galaxy are prevalent, all offering an extensive selection of diverse models to cater to a variety of budgets. According to how high tech the device you select, costs can start from an affordable sum to thousands of pounds.

"It makes me crazy, I can't switch off."

"It provides solace… It's like a companion supporting me."

"Please don't notify me about a restless night."

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

A Sea of Statistics

My thoughts on my own device? Currently, frustrating. It's indicating I'm not hitting my target, causing me to question whether the overhead branches I'm running below are interfering with my location tracking.

A vast number of us strap these small monitors onto our wrists and wear them all day and night, ostensibly unconcerned with the fact they're constantly monitoring us.

Long past are the days when we depended on them solely to give us an rough count of our pedometer reading. Currently, they can track our nightly rest, stress levels, oxygen saturation, our body battery.

It's difficult to find a bodily function they aren't designed to measure.

But are they able to do what they advertise? And are the numbers we obsess over a faithful picture of the truth? Do they enhance our mental and physical wellbeing, or do the avalanche of measurements and cheerleading alerts just add to our everyday anxiety?

Addiction or Aid?

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

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

Until she found out she could adjust the settings, her smartwatch repeatedly informed her she was being insufficiently productive enough. Later on, the watch frequently reports her she's had a restless night.

"I am caring for a infant, it's unnecessary for me to be informed I've not slept," she says. "That fact is perfectly well."

Is it not possible to just take it off?

"I could, I suppose, but I have this push-pull dynamic with it," she continues. "I value it for its exercise data, but I'm unsure whether the myriad other functions it can now do is perhaps too much for me."

The Technology Behind the Tracking

Different brands of smartwatch has its own novel way of measuring your vitals and interpreting your data, but the most use detectors on the back of the watch.

They usually emit minute LED lights onto your arm which can monitor blood flow, detecting your pulse rate. Sophisticated devices detect changes in the skin conductance that passes over the skin to get an idea of your nervous system activity.

The Professional Viewpoint

A professor says that in general for smartwatches, it's a "delicate equilibrium" - while the rapidly advancing tech could realistically aid early diagnosis, "detecting disease before we show symptoms", it could also turn us device users into the "worried well".

He points out that some of the latest wearables can perform tests like heart rhythm analysis, which regularly monitor how stable the heart is. They can alert if someone is experiencing an irregular rhythm, where there is abnormal electrical activity in the heart causing an irregular heartbeat.

This does not automatically signal someone is imminently going to suffer a heart attack, but it can give an preliminary indication they might be more at risk of a stroke in the future.

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

"I remain sceptical that having the capacity to monitor so many metrics is such a good idea," he says.

A professor focusing on wearable tech concurs. Her work into the effect of wearable tech on a cohort of cardiovascular patients suggested a minority of those who were given devices to monitor their cardiac function experienced heightened worry and were "had a higher tendency to use doctor's time".

She identified a vicious circle with her patients - they noticed a alarming metric on their watch. They grew concerned. Their pulse increased. They got increasingly anxious. They looked a second time, and their anxiety increased again.

"If we see numbers about ourselves that we lack context for then, naturally, we are going to want to know more," the psychologist says. "We look, we re-check - it becomes a feedback loop."