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A sense of feeling of anticipation. Apparent is the cold breath exhaled by my rivals as they perform the "starting line" shuffle on the beginning point.

A rapid movement of the hips.

I'm lined up for my local Saturday morning race and I mean business. It's almost time...

Wait a second. I have to sort my tracker. As does the person next to me.

The person behind us expresses impatience. I refuse to go until… there! GPS ready, I'm off.

During the scramble, it's hard to find a person without a fitness tracker on it. And this isn't only us runners who wear them.

We're witnessing a booming, multi-billion pound market. Brands like Apple Watch dominate, each with an wide selection of diverse devices to suit a spectrum of needs. According to how advanced the device you select, price tags can vary between £100 to thousands of pounds.

"It makes me crazy, I can't relax."

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

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

Just some of the comments people have shared from other smartwatch wearers when I question what they think of theirs.

The Data Dilemma

My current opinion on my own device? At this moment, irritating. It's reporting my speed is wrong, making me wonder whether the trees I'm running below are blocking my satellite signal.

Millions of us strap these compact devices onto our arms and use them constantly, apparently at ease with the fact they're perpetually monitoring us.

A distant memory are the days when we used them solely to give us an idea of our daily steps. Today, they can analyse our sleep patterns, blood pressure, glucose levels, our recovery score.

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

But can they do what they advertise? And are the statistics we analyse a faithful picture of reality? Do they enhance our overall health, or do the multitude of measurements and motivational messages just add to our sense of overwhelm?

Addiction or Aid?

"I find myself getting a quite preoccupied with mine," an individual admits.

While she appreciates how her device records her exercise, she finds some of its other functions "overwhelming" at times - a feeling first discovered during a significant period.

Before she realised she could put it into a specific mode, her smartwatch constantly alerted her she was failing to be energetic enough. In a new phase, the watch keeps telling her she's had a bad night's sleep.

"I've got a six-month old, I don't need to be told my sleep was poor," she says. "That fact is only too well."

Couldn't she just remove it?

"I suppose I could, theoretically, but I'm in this complicated dynamic with it," she says. "I love it for its workout tracking, I sometimes question whether all the other things it can now do is possibly excessive for me."

The Technology Behind the Tracking

Different brands of smartwatch has its own unique way of measuring your bodily functions and analysing your data, but the most use detectors on the underside of the watch.

They typically project small, green LED lights onto your arm which can detect blood flow, detecting your pulse rate. Sophisticated devices measure changes in the bioimpedance that flows through the skin to assess your recovery state.

The Professional Viewpoint

A professor says that for most people for smartwatches, it's a "fine balance" - while the ever-evolving tech could actually aid early diagnosis, "detecting disease before we show symptoms", it could also turn us the tracked into the "concerned but fine".

He points out that the most advanced wearables can carry out tests like electrocardiograms (ECGs), which continuously monitor how stable the heart is. They can notify if someone is experiencing an irregular rhythm, where there is erratic signals in the heart causing an arrhythmia.

This does not necessarily indicate someone is imminently going to suffer a heart attack, but it can give an preliminary indication they might be more vulnerable of a blood clot in the long term.

But how to make sense of these numbers is not straightforward. The expert concerns that as additional features are introduced, people may not be able to fully contextualise their data.

"I remain sceptical that having the capacity to monitor so many things is such a beneficial thing," he says.

A professor studying cardiology agrees. Her work into the influence of wearable tech on a cohort of cardiovascular patients suggested a noticeable percentage of those who were given devices to monitor their cardiac function experienced increased anxiety and were "had a higher tendency to use healthcare resources".

She observed a cycle with her patients - they noticed a alarming metric on their watch. They grew concerned. Their pulse rose. They got more worried. They re-examined the data, and their anxiety went up again.

"If we see data about ourselves that we don't really understand then, naturally, we are going to seek clarification," the psychologist says. "We look, we obsess - it becomes a vicious cycle."