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There's a feeling of anticipation. I can see the frosty air coming from my fellow runners as they do the "about to run" shuffle on the start line.

A rapid flick of the hips.

I'm lined up for my local 5km community parkrun and I'm serious. Three, two, one...

Wait a second. I need to sort my tracker. So does the runner beside me.

The person waiting tuts. I won't start until… there! Signal acquired, and I'm running.

During the scramble, it's challenging to find a wrist without a fitness tracker on it. And it's not just us runners who wear them.

This is a booming, multi-billion dollar sector. Companies like Samsung Galaxy are prevalent, all offering an broad selection of different devices to fit a range of lifestyles. Depending on how advanced the device you go for, prices can range from £100 to a small fortune.

"It drives me insane, it's impossible to relax."

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

"Stop telling me I've experienced a bad night's sleep."

Just some of the comments I've received from fellow smartwatch wearers when I question what they their opinion is on theirs.

The Data Dilemma

My feelings on mine? Right now, annoying. It's reporting my speed is wrong, making me wonder whether the trees I'm running below are disrupting my location tracking.

A vast number of us attach these small monitors onto our arms and keep them on 24/7, seemingly comfortable with the fact they're constantly recording us.

Long past are the days when we relied on them only to give us an idea of our pedometer reading. Now, they can track our sleep quality, stress levels, oxygen saturation, our recovery score.

It's tricky to find a physical metric they don't track.

But do they do what they say they do? And are the numbers we scrutinise a accurate representation of our actual health? Do they boost our mental and physical wellbeing, or do the plethora of measurements and cheerleading alerts just increase our daily stresses?

A Love-Hate Relationship

"I become a a little obsessed with mine," one user confesses.

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

Before she realised she could adjust the settings, her smartwatch repeatedly informed her she was being insufficiently active enough. In a new phase, the watch keeps telling her she's had a restless night.

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

Couldn't she just stop wearing it?

"It's possible, theoretically, but I have this love-hate relationship with it," she says. "I love it for its exercise data, I sometimes question whether the myriad other functions it can now do is possibly overkill for me."

How Do They Work?

Different brands of smartwatch has its own novel way of monitoring your health metrics and analysing your data, but the most use sensors on the underside of the watch.

They typically project minute LED lights onto your skin which can detect capillary action, recording your BPM. Sophisticated devices detect changes in the bioimpedance that runs through the skin to assess your nervous system activity.

The Professional Viewpoint

A data scientist says that in general for smartwatches, it's a "delicate equilibrium" - while the rapidly advancing tech could potentially save lives, "spotting abnormalities before we feel unwell", it could also turn us watch wearers into the "anxious healthy".

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

This does not necessarily indicate someone is imminently going to suffer a cardiac event, but it can give an early warning they might be more susceptible of a blood clot in the long term.

But how to understand these numbers is complicated. The expert fears that as more functions are introduced, people may find it hard to fully understand their data.

"I have some doubts that the ability to monitor so much data is such a positive development," he says.

A clinical psychologist studying cardiology agrees. Research into the effect of wearable tech on a set of individuals with health issues suggested a noticeable percentage of those who were given devices to monitor their heart health experienced heightened worry and were "had a higher tendency to use doctor's time".

She identified a pattern with her patients - they saw a concerning reading on their watch. They felt anxious. Their heart rate increased. They got more worried. They looked a second time, and their heart rate went up again.

"If we see numbers about ourselves that we don't really understand then, of course, we are going to seek clarification," the psychologist says. "We monitor, we re-check - it becomes a self-fulfilling prophecy."