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There's a nervous excitement. I can see the chilled vapour emanating from my rivals as they execute the "starting line" jiggle on the beginning point.

A rapid movement of the hips.

I'm participating in my local weekly parkrun event and I'm serious. The countdown begins...

Wait a second. I have to sort my watch. As does the runner beside me.

The person waiting expresses impatience. I won't start until… yes! Connection established, away I go.

Amidst the crowd, it's hard to find a wrist without a fitness tracker on it. And this extends beyond us athletes who use them.

This is a thriving, multi-billion dollar sector. Names like Garmin are prevalent, each with an extensive array of different devices to fit a range of lifestyles. According to how high tech the watch you choose, prices can start from £100 to a small fortune.

"I find it infuriating, I can't switch off."

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

"Stop telling me about a poor sleep."

Just some of the responses I've had from other device users when I ask what they feel about theirs.

The Monitoring Conundrum

My feelings on mine? Currently, irritating. It's reporting my speed is wrong, causing me to question whether the foliage I'm passing under are interfering with my GPS connection.

A vast number of us strap these small devices onto our arms and use them constantly, seemingly at ease with the fact they're constantly monitoring us.

Gone are the days when we relied on them only to give us an rough count of our step count. Today, they can track our sleep quality, stress levels, glucose levels, our recovery score.

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

But do they do what they say they do? And are the data points we analyse a true reflection of the truth? Do they improve our overall health, or do the avalanche of metrics and cheerleading alerts just add to our daily stresses?

A Complicated Bond

"I find myself getting a bit fixated with mine," a wearer admits.

While she values how her device monitors her workouts, she finds some of its other capabilities "overwhelming" at times - a feeling that became apparent during a significant period.

Before she realised she could change its configuration, her smartwatch repeatedly informed her she was not being energetic enough. In a new phase, 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 informed I'm tired," she says. "That fact is only too well."

Is it not possible to just remove it?

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

Inside the Device

Different brands of smartwatch has its own novel way of measuring your health metrics and interpreting your data, but the majority use optical sensors on the back of the watch.

They usually project small, green LED lights onto your wrist which can observe pulsation, recording your heartbeat. Sophisticated devices detect changes in the bioimpedance that flows through the skin to get an idea of your nervous system activity.

A Fine Balance

A data scientist says that overall for smartwatches, it's a "delicate equilibrium" - while the rapidly advancing tech could realistically prevent illness, "identifying issues before we show symptoms", it could also turn us the tracked into the "concerned but fine".

He points out that newer wearables can carry out tests like medical-grade monitoring, which constantly monitor how healthy the heart is. They can flag if someone is experiencing a heart arrhythmia, where there is abnormal 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 vulnerable of a stroke in the future.

But how to interpret these numbers is complex. The expert concerns that as more functions are added, people may not be able to fully comprehend their data.

"I remain sceptical that being able to monitor so much data is such a beneficial thing," he says.

A professor specialising in cardiology echoes this sentiment. Research into the effect of wearable tech on a cohort of individuals with health issues suggested a significant portion of those who were given devices to monitor their heart health experienced greater stress and were "had a higher tendency to use medical services".

She noted a cycle with her patients - they spotted a concerning reading on their watch. They grew concerned. Their BPM rose. They got increasingly anxious. They re-examined the data, and their heart rate went up again.

"Upon viewing stats about ourselves that we don't really understand then, understandably, we are going to seek clarification," the psychologist says. "We monitor, we check again - it becomes a feedback loop."