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An atmosphere of nervous excitement. Apparent is the chilled vapour exhaled by my rivals as they perform the "starting line" shuffle on the start line.

A rapid flick of the hips.

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

Hold on. I must start my tracker. So does the guy beside me.

The person behind us sighs. I won't start until… yes! Connection established, and I'm running.

Amidst the crowd, it's difficult to see a arm without a wearable on it. And this isn't only us athletes who use them.

This is a thriving, massive sector. Names like Garmin are prevalent, all offering an extensive range of different devices to fit a spectrum of lifestyles. According to how advanced the watch you go for, prices can range from £100 to a small fortune.

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

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

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

A small sample of the responses I've received from fellow tracker enthusiasts when I question what they feel about theirs.

A Sea of Statistics

My feelings on mine? Right now, irritating. It's reporting I'm not hitting my target, leading me to doubt whether the overhead branches I'm passing under are blocking my satellite signal.

Millions of us attach these small gadgets onto our arms and keep them on 24/7, apparently unconcerned with the fact they're perpetually tracking us.

A distant memory are the days when we used them solely to give us an idea of our step count. Currently, they can analyse our sleep patterns, blood pressure, heart rate variability (HRV), our VO2 max.

It's tricky to find a bodily function they don't track.

But do they do what they claim to do? And are the numbers we analyse a true reflection of our actual health? Do they enhance our overall health, or do the multitude of measurements and constant notifications just increase our sense of overwhelm?

Addiction or Aid?

"I find myself getting a quite fixated with mine," a wearer confesses.

While she loves how her device tracks her workouts, she finds some of its other features "excessive" at times - a feeling first discovered during a pregnancy.

Prior to discovering she could put it into a specific mode, her smartwatch repeatedly informed her she was failing to be active enough. Later on, the watch frequently reports her she's had a bad night's sleep.

"I have a young baby, there's no point to be notified I'm tired," she says. "I know that only too well."

Why doesn't she just remove it?

"It's possible, I suppose, but I have this push-pull dynamic with it," she says. "I appreciate it for its exercise data, but I'm unsure whether the additional features it can now do is possibly too much for me."

The Technology Behind the Tracking

Different brands of smartwatch has its own proprietary way of monitoring your bodily functions and processing your data, but the most use optical sensors on the back of the watch.

They commonly shine small, green LED lights onto your skin which can monitor blood flow, recording your BPM. Higher-end devices detect changes in the skin conductance that flows through the skin to gauge your recovery state.

The Professional Viewpoint

A data scientist says that in general for smartwatches, it's a "fine balance" - while the ever-evolving tech could potentially save lives, "spotting abnormalities before we notice anything", it could also turn us the tracked into the "anxious healthy".

He points out that some of the latest wearables can carry out tests like medical-grade monitoring, which regularly monitor how stable the heart is. They can flag if someone is experiencing atrial fibrillation (AF), where there is irregular impulses in the heart causing an arrhythmia.

This does not necessarily indicate someone is on the verge of a heart attack, but it can give an early warning they might be more susceptible of a heart problem in the long term.

But how to make sense of these readings is not straightforward. The expert worries that as more functions are incorporated, people may find it hard to fully comprehend their data.

"I remain sceptical that the ability to monitor so much data is such a good idea," he says.

A clinical psychologist studying wearable tech concurs. A study into the effect of wearable tech on a set of cardiovascular patients suggested a significant portion of those who were given devices to monitor their condition experienced heightened worry and were "had a higher tendency to use doctor's time".

She identified a vicious circle with her patients - they spotted a worrying figure on their watch. They became worried. Their pulse went up. They got more worried. They checked again, and their reading rose further.

"If we see numbers about ourselves that we can't properly interpret then, understandably, we are going to seek clarification," the psychologist says. "We check, we check again - it becomes a vicious cycle."