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An atmosphere of feeling of anticipation. I can see the frosty air coming from my rivals as they perform the "starting line" wiggle on the start line.

A rapid movement of the hips.

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

Wait a second. I must adjust my tracker. So does the person next to me.

The person waiting expresses impatience. I'm not moving until… there! Signal acquired, away I go.

During the scramble, it's hard to see a wrist without a smartwatch on it. And this extends beyond us runners who rely on them.

We're witnessing a explosive, massive market. Brands like Garmin dominate, each with an wide array of diverse devices to suit a variety of lifestyles. Depending on how feature-packed the model you choose, prices can vary between £100 to a significant investment.

"It makes me crazy, I'm unable to stop checking."

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

"Stop telling me I've experienced a poor sleep."

A small sample of the reactions I've received from like-minded tracker enthusiasts when I question what they think of theirs.

The Monitoring Conundrum

My feelings on my own device? Right now, annoying. It's reporting I'm off pace, leading me to doubt whether the overhead branches I'm passing under are blocking my location tracking.

A vast number of us fasten these little gadgets onto our arms and keep them on 24/7, seemingly at ease with the fact they're perpetually monitoring us.

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

It's tricky to find a bodily function they fail to monitor.

But do they do what they say they do? And are the data points we obsess over a accurate representation of our actual health? Do they boost our overall health, or do the plethora of readings and motivational messages just contribute to our daily stresses?

A Love-Hate Relationship

"I do get a quite fixated with mine," a wearer admits.

While she values how her device tracks her exercise, she finds some of its other functions "excessive" at times - a feeling initially realised during a significant period.

Until she found out she could adjust the settings, her smartwatch kept telling her she was being insufficiently energetic enough. In a new phase, the watch keeps telling her she's had a restless night.

"I am caring for a six-month old, there's no point to be told I'm tired," she says. "That fact is perfectly well."

Why doesn't she just stop wearing it?

"It's possible, I suppose, but I'm in this love-hate relationship with it," she explains. "I value it for its workout tracking, I just wonder whether all the other things it can now do is maybe overkill for me."

How Do They Work?

Every device of smartwatch has its own proprietary way of tracking your bodily functions and interpreting your data, but the vast bulk use detectors on the reverse of the watch.

They commonly project small, green LED lights onto your skin which can observe capillary action, detecting your heartbeat. Sophisticated devices measure changes in the electrical current that passes over the skin to assess your nervous system activity.

Expert Perspectives

A data scientist says that overall for smartwatches, it's a "delicate equilibrium" - while the continuously improving tech could potentially aid early diagnosis, "detecting disease 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 notify if someone is experiencing atrial fibrillation (AF), where there is erratic signals in the heart causing an arrhythmia.

This does not automatically signal someone is on the verge of a cardiac event, but it can give an advance notice they might be more at risk of a stroke in the years to come.

But how to interpret these readings is complex. The expert fears that as more functions are added, people may find it hard to fully understand their data.

"I have some doubts that having the capacity to monitor so many things is such a positive development," he says.

A health researcher specialising in cardiology agrees. Her work into the influence of wearable tech on a specific group of heart condition patients suggested a minority of those who were given devices to monitor their condition experienced heightened worry and were "more inclined to use doctor's time".

She noted a vicious circle with her patients - they saw a alarming metric on their watch. They grew concerned. Their BPM increased. They got increasingly anxious. They looked a second time, and their heart rate went up again.

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