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A sense of feeling of anticipation. Visible is the frosty air coming from my fellow runners as they execute the "pre-race" wiggle on the beginning point.

A quick twitch of the hips.

I'm lined up for my local weekly parkrun event and I mean business. Three, two, one...

Hold on. I need to sort my device. As does the runner alongside me.

The person in the line sighs. I'm not moving until… yes! Signal acquired, away I go.

During the scramble, it's difficult to spot a arm without a fitness tracker on it. And this extends beyond us participants who wear them.

It's a booming, multi-billion dollar sector. Companies like Samsung Galaxy lead the market, all offering an extensive array of diverse models to suit a range of needs. Based on how high tech the watch you select, prices can range from £100 to thousands of pounds.

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

"It reassures me… It feels like a friend supporting me."

"Please don't notify me I've experienced a bad night's sleep."

A small sample of the responses I've had from other device users when I ask what they their opinion is on theirs.

The Monitoring Conundrum

My thoughts on mine? At this moment, irritating. It's reporting I'm not hitting my target, causing me to question whether the trees I'm passing under are blocking my GPS connection.

A vast number of us attach these compact monitors onto our arms and use them all day and night, apparently unconcerned with the fact they're constantly tracking us.

Gone are the days when we relied on them solely to give us an rough count of our pedometer reading. Today, they can measure our nightly rest, stress levels, heart rate variability (HRV), our VO2 max.

It's a challenge to find a physical metric they fail to monitor.

But are they able to do what they claim to do? And are the statistics we analyse a faithful picture of our actual health? Do they boost our overall health, or do the multitude of metrics and motivational messages just add to our everyday anxiety?

A Love-Hate Relationship

"I become a bit fixated with mine," a wearer reveals.

While she appreciates how her device monitors her exercise, she finds some of its other capabilities "daunting" at times - a feeling initially realised during a pregnancy.

Before she realised she could adjust the settings, her smartwatch constantly alerted her she was being insufficiently energetic enough. Later on, the watch insists her she's had a poor sleep score.

"I've got a young baby, there's no point to be notified I've not slept," she says. "I'm acutely aware perfectly well."

Couldn't she just stop wearing it?

"It's possible, theoretically, but I'm in this complicated dynamic with it," she continues. "I love it for its exercise data, I just wonder whether all the other things it can now do is maybe too much for me."

Inside the Device

Every device of smartwatch has its own proprietary way of measuring your health metrics and interpreting your data, but the vast bulk use optical sensors on the reverse of the watch.

They usually project small, green LED lights onto your wrist which can observe capillary action, detecting your BPM. Sophisticated devices analyse changes in the bioimpedance that flows through the skin to get an idea of your nervous system activity.

The Professional Viewpoint

One expert says that for most people for smartwatches, it's a "difficult line" - while the ever-evolving tech could realistically aid early diagnosis, "identifying issues before we notice anything", it could also turn us watch wearers into the "concerned but fine".

He points out that newer wearables can perform tests like heart rhythm analysis, which regularly monitor how normal the heart is. They can notify if someone is experiencing an irregular rhythm, where there is irregular impulses 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 advance notice they might be more vulnerable of a blood clot in the years to come.

But how to understand these figures is not straightforward. The expert worries that as more functions are incorporated, people may not be able to fully comprehend their data.

"I have some doubts that being able to monitor so many metrics is such a beneficial thing," he says.

A health researcher focusing on patient behaviour concurs. Her work into the influence of wearable tech on a cohort of heart condition patients suggested a significant portion of those who were given devices to monitor their heart health experienced greater stress and were "far more likely to use healthcare resources".

She observed a cycle with her patients - they saw a concerning reading on their watch. They felt anxious. Their pulse rose. They got increasingly anxious. They checked again, and their anxiety rose further.

"Upon viewing data about ourselves that we don't really understand then, naturally, we are going to want to know more," the psychologist says. "We monitor, we check again - it becomes a vicious cycle."