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A sense of feeling of anticipation. Apparent is the frosty air exhaled by my fellow runners as they execute the "starting line" shuffle on the beginning point.

A swift twitch of the hips.

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

Wait a second. I must sort my device. As does the runner beside me.

The person behind us expresses impatience. I won't start until… there! Signal acquired, and I'm running.

Amidst the crowd, it's difficult to find a arm without a wearable on it. And it's not just us runners who use them.

It's a booming, massive market. Names like Garmin are prevalent, each with an broad selection of diverse models to fit a range of budgets. According to how feature-packed the device you select, costs can start from a hundred pounds to a significant investment.

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

"It provides solace… It feels like a friend encouraging me."

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

Just some of the comments I've had from fellow device users when I ask what they their opinion is on theirs.

The Monitoring Conundrum

My current opinion on mine? At this moment, annoying. It's indicating my speed is wrong, making me wonder whether the trees along my route are blocking my location tracking.

A vast number of us strap these little devices onto our arms and wear them 24/7, ostensibly comfortable with the fact they're constantly recording us.

Long past are the days when we relied on them only to give us an estimation of our daily steps. Currently, they can measure our sleep quality, stress levels, glucose levels, our VO2 max.

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

But are they able to do what they claim to do? And are the data points we obsess over a faithful picture of our actual health? Do they boost our overall health, or do the multitude of readings and constant notifications just contribute to our daily stresses?

Addiction or Aid?

"I do get a quite obsessed with mine," an individual confesses.

While she values how her device tracks her runs, she finds some of its other functions "daunting" at times - a feeling initially realised 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. Now, the watch frequently reports her she's had a bad night's sleep.

"I have a six-month old, it's unnecessary for me to be notified my sleep was poor," she says. "I know that only too well."

Couldn't she just remove it?

"I suppose I could, perhaps, but I've got this push-pull dynamic with it," she explains. "I value it for its workout tracking, I sometimes question whether the additional features it can now do is maybe excessive for me."

The Technology Behind the Tracking

Each model of smartwatch has its own novel way of measuring your bodily functions and processing your data, but the vast bulk use optical sensors on the back of the watch.

They commonly emit small, green LED lights onto your wrist which can detect pulsation, identifying your BPM. Sophisticated devices measure changes in the electrical current that flows through the skin to assess your nervous system activity.

The Professional Viewpoint

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

He points out that the most advanced wearables can conduct tests like medical-grade monitoring, which constantly monitor how stable the heart is. They can alert if someone is experiencing a heart arrhythmia, where there is abnormal electrical activity in the heart causing an irregular heartbeat.

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

But how to understand these readings is complex. The expert fears that as further capabilities are incorporated, people may struggle to fully understand their data.

"I'm not entirely convinced that the ability to monitor so much data is such a good idea," he says.

A professor specialising in cardiology agrees. Research into the impact of wearable tech on a set of cardiovascular patients suggested a noticeable percentage of those who were given devices to monitor their cardiac function experienced greater stress and were "more inclined to use healthcare resources".

She noted a pattern with her patients - they spotted a alarming metric on their watch. They grew concerned. Their heart rate went up. They got even more concerned. They re-examined the data, and their heart rate went up again.

"When people are presented with data about ourselves that we lack context for then, naturally, we are going to want to know more," the psychologist says. "We monitor, we re-check - it becomes a self-fulfilling prophecy."