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There's a building tension. I can see the frosty air coming from my competitors as they execute the "about to run" shuffle on the beginning point.

A quick flick of the hips.

I'm at my local 5km community parkrun and I'm serious. It's almost time...

Wait a second. I need to sort my watch. So does the person next to me.

The person waiting tuts. I refuse to go until… there! Signal acquired, and I'm running.

During the scramble, it's challenging to see a person without a fitness tracker on it. And it's not just us participants who rely on them.

This is a booming, multi-billion pound market. Companies like Garmin lead the market, featuring an broad selection of diverse devices to cater to a variety of lifestyles. Based on how advanced the device you select, price tags can start from an affordable sum to a small fortune.

"It makes me crazy, it's impossible to relax."

"It provides solace… It's like a friend guiding me."

"Please don't notify me about a poor sleep."

Just some of the reactions people have shared from fellow tracker enthusiasts when I ask what they feel about theirs.

The Data Dilemma

My feelings on my own device? Right now, annoying. It's telling me I'm not hitting my target, causing me to question whether the trees along my route are interfering with my satellite signal.

Countless individuals of us attach these small monitors onto our wrists and wear them constantly, apparently unconcerned with the fact they're continuously recording us.

Gone are the days when we used them exclusively to give us an idea of our pedometer reading. Today, they can track our nightly rest, heart rate, glucose levels, our VO2 max.

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

But are they able to do what they claim to do? And are the data points we analyse a faithful picture of reality? Do they improve our daily wellness, or do the multitude of measurements and cheerleading alerts just increase our daily stresses?

A Complicated Bond

"I find myself getting a bit preoccupied with mine," an individual admits.

While she appreciates how her device tracks her workouts, she finds some of its other functions "excessive" at times - a feeling initially realised during a pregnancy.

Before she realised she could put it into a specific mode, her smartwatch constantly alerted her she was failing to be energetic enough. In a new phase, the watch keeps telling her she's had a restless night.

"I've got a infant, it's unnecessary for me to be informed my sleep was poor," she says. "I'm acutely aware all too clearly."

Is it not possible to just take it off?

"I could, theoretically, but I've got this push-pull dynamic 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 possibly too much for me."

The Technology Behind the Tracking

Each model of smartwatch has its own novel way of monitoring your vitals and processing your data, but the vast bulk use optical sensors on the reverse of the watch.

They usually emit small, green LED lights onto your skin which can monitor capillary action, detecting your pulse rate. Higher-end devices analyse changes in the electrical current that passes over the skin to gauge your stress levels.

The Professional Viewpoint

A data scientist says that for most people for smartwatches, it's a "difficult line" - while the continuously improving tech could realistically prevent illness, "spotting abnormalities before we show symptoms", it could also turn us the tracked into the "worried well".

He points out that newer wearables can perform tests like heart rhythm analysis, which constantly monitor how healthy the heart is. They can flag if someone is experiencing an irregular rhythm, where there is erratic electrical activity in the heart causing an arrhythmia.

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

But how to interpret these readings is not straightforward. The expert worries that as further capabilities are introduced, people may not be able to fully contextualise their data.

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

A professor studying patient behaviour agrees. 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 heart health experienced greater stress and were "more inclined to use doctor's time".

She noted a vicious circle with her patients - they saw a concerning reading on their watch. They became worried. Their BPM went up. They got more worried. They re-examined the data, and their anxiety went up again.

"When people are presented with stats about ourselves that we can't properly interpret then, naturally, we are going to seek clarification," the psychologist says. "We look, we check again - it becomes a self-fulfilling prophecy."