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A sense of nervous excitement. Apparent is the chilled vapour coming from my fellow runners as they do the "about to run" jiggle on the start line.

A swift movement of the hips.

I'm participating in my local Saturday morning race and I mean business. The countdown begins...

Oh, hang on. I need to start my device. The same goes for the person next to me.

The person in the line tuts. I refuse to go until… done! Connection established, away I go.

Amidst the crowd, it's difficult to see a arm without a smartwatch on it. And this extends beyond us athletes who wear them.

This is a thriving, multi-billion dollar market. Companies like Apple Watch lead the market, each with an wide selection of different devices to suit a variety of budgets. Based on how feature-packed the device you go for, price tags can start from a hundred pounds to a significant investment.

"I find it infuriating, it's impossible to stop checking."

"It reassures me… It feels like a companion encouraging me."

"Stop telling me about a bad night's sleep."

A handful of the comments I've received from other tracker enthusiasts when I question what they think of theirs.

A Sea of Statistics

My thoughts on mine? At this moment, frustrating. It's reporting my speed is wrong, causing me to question whether the trees I'm running below are disrupting my satellite signal.

A vast number of us attach these compact devices onto our arms and use them 24/7, seemingly comfortable with the fact they're constantly recording us.

A distant memory are the days when we used them exclusively to give us an rough count of our step count. Now, they can analyse our nightly rest, heart rate, heart rate variability (HRV), our recovery score.

It's a challenge to find a physical metric they aren't designed to measure.

But are they able to do what they claim to do? And are the numbers we analyse a true reflection of the truth? Do they boost our overall health, or do the avalanche of readings and motivational messages just add to our sense of overwhelm?

Addiction or Aid?

"I do get a a little preoccupied with mine," an individual confesses.

While she loves how her device records her exercise, she finds some of its other functions "daunting" at times - a feeling first discovered during a pregnancy.

Before she realised she could change its configuration, her smartwatch repeatedly informed her she was not being productive enough. Later on, the watch frequently reports her she's had a poor sleep score.

"I am caring for a six-month old, I don't need to be notified I've not slept," she says. "That fact is only too well."

Is it not possible to just stop wearing it?

"It's possible, I suppose, but I have this complicated dynamic with it," she explains. "I love it for its workout tracking, I just wonder whether the myriad other functions it can now do is possibly too much for me."

The Technology Behind the Tracking

Each model of smartwatch has its own unique way of tracking your health metrics and processing your data, but the majority use optical sensors on the underside of the watch.

They commonly emit tiny, coloured LED lights onto your wrist which can monitor blood flow, recording your heartbeat. Higher-end devices measure changes in the electrical current that runs through the skin to get an idea of your stress levels.

A Fine Balance

One expert says that in general for smartwatches, it's a "difficult line" - while the continuously improving tech could realistically aid early diagnosis, "spotting abnormalities before we show symptoms", it could also turn us the tracked into the "worried well".

He points out that newer wearables can carry out tests like electrocardiograms (ECGs), which constantly monitor how normal the heart is. They can notify if someone is experiencing a heart arrhythmia, where there is erratic electrical activity in the heart causing an uneven pulse.

This does not automatically signal someone is on the verge of a heart attack, but it can give an preliminary indication they might be more susceptible of a blood clot in the future.

But how to understand these readings is complicated. The expert fears that as further capabilities are added, people may not be able to fully understand their data.

"I'm not entirely convinced that being able to monitor so much data is such a positive development," he says.

A clinical psychologist specialising in patient behaviour concurs. A study 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 cardiac function experienced heightened worry and were "had a higher tendency to use doctor's time".

She identified a vicious circle with her patients - they saw a worrying figure on their watch. They grew concerned. Their heart rate went up. They got even more concerned. They re-examined the data, and their reading rose further.

"If we see stats about ourselves that we can't properly interpret then, naturally, we are going to want to know more," the psychologist says. "We check, we obsess - it becomes a vicious cycle."