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An atmosphere of building tension. Apparent is the chilled vapour emanating from my rivals as they perform the "about to run" jiggle on the starting line.

A rapid movement of the hips.

I'm participating in my local weekly parkrun event and I mean business. It's almost time...

Wait a second. I must adjust my tracker. As does the person next to me.

The person behind us expresses impatience. I refuse to go until… yes! Connection established, I'm off.

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

We're witnessing a explosive, multi-billion pound sector. Companies like Apple Watch are prevalent, featuring an broad array of diverse versions to fit a spectrum of budgets. Depending on how advanced the watch you go for, prices can vary between an affordable sum to thousands of pounds.

"I find it infuriating, I can't relax."

"It reassures me… It's like a supporter guiding me."

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

A handful of the reactions I've received from fellow tracker enthusiasts when I ask what they think of theirs.

The Monitoring Conundrum

My thoughts on mine? Currently, irritating. It's telling me I'm off pace, causing me to question whether the overhead branches along my route are disrupting my location tracking.

Countless individuals of us attach these little monitors onto our arms and wear them all day and night, ostensibly at ease with the fact they're constantly recording us.

Long past are the days when we relied on them exclusively to give us an estimation of our pedometer reading. Today, they can measure our sleep patterns, blood pressure, oxygen saturation, our VO2 max.

It's tricky to find a health indicator they aren't designed to measure.

But are they able to do what they advertise? And are the data points we analyse a accurate representation of reality? Do they enhance our overall health, or do the multitude of readings and constant notifications just add to our daily stresses?

A Love-Hate Relationship

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

While she values how her device tracks her workouts, she finds some of its other features "daunting" at times - a feeling initially realised during a major life event.

Before she realised she could put it into a specific mode, her smartwatch constantly alerted her she was not being productive enough. Now, the watch frequently reports her she's had a bad night's sleep.

"I have a young baby, I don't need to be informed I'm tired," she says. "I know that only too well."

Is it not possible to just remove it?

"I suppose I could, perhaps, but I've got this complicated dynamic with it," she continues. "I love it for its fitness insights, I sometimes question whether all the other things it can now do is possibly overkill for me."

The Technology Behind the Tracking

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

They commonly project tiny, coloured LED lights onto your wrist which can observe blood flow, identifying your BPM. Sophisticated devices analyse changes in the skin conductance that flows through the skin to get an idea of your recovery state.

Expert Perspectives

A data scientist says that in general for smartwatches, it's a "difficult line" - while the continuously improving tech could actually prevent illness, "identifying issues before we show symptoms", it could also turn us device users into the "concerned but fine".

He points out that the most advanced wearables can conduct tests like heart rhythm analysis, which regularly monitor how normal the heart is. They can alert if someone is experiencing a heart arrhythmia, where there is abnormal electrical activity in the heart causing an arrhythmia.

This does not mean someone is imminently going to suffer a heart attack, but it can give an early warning they might be more at risk of a stroke in the years to come.

But how to make sense of these figures is complicated. The expert fears that as more functions are added, people may struggle to fully contextualise their data.

"I'm not entirely convinced that having the capacity to monitor so much data is such a good idea," he says.

A clinical psychologist focusing on cardiology agrees. Her work into the effect of wearable tech on a set of heart condition patients suggested a noticeable percentage of those who were given devices to monitor their condition experienced heightened worry and were "more inclined to use doctor's time".

She noted a vicious circle with her patients - they noticed a concerning reading on their watch. They grew concerned. Their heart rate rose. They got even more concerned. They looked a second time, and their heart rate increased again.

"If we see numbers about ourselves that we don't really understand then, understandably, we are going to want to know more," the psychologist says. "We look, we check again - it becomes a vicious cycle."