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A sense of feeling of anticipation. Apparent is the frosty air coming from my rivals as they execute the "about to run" jiggle on the beginning point.

A quick twitch of the hips.

I'm at my local 5km community parkrun and I mean business. It's almost time...

Hold on. I must adjust my tracker. As does the person beside me.

The person behind us tuts. I'm not moving until… there! GPS ready, I'm off.

During the scramble, it's difficult to spot a arm without a fitness tracker on it. And it's not just us participants who rely on them.

This is a booming, multi-billion dollar sector. Companies like Garmin dominate, featuring an extensive array of diverse models to suit a spectrum of lifestyles. Depending on how high tech the model you select, price tags can range from £100 to thousands of pounds.

"It drives me insane, I can't relax."

"It reassures me… It acts as a supporter supporting me."

"I wish it wouldn't say about a poor sleep."

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

The Monitoring Conundrum

My thoughts on mine? At this moment, annoying. It's reporting I'm off pace, causing me to question whether the foliage along my route are blocking my satellite signal.

Millions of us attach these little devices onto our arms and keep them on 24/7, apparently at ease with the fact they're constantly tracking us.

A distant memory are the days when we depended on them solely to give us an idea of our daily steps. Now, they can measure our sleep quality, heart rate, oxygen saturation, our recovery score.

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

But are they able to do what they say they do? And are the numbers we scrutinise a faithful picture of the truth? Do they improve our daily wellness, or do the multitude of metrics and motivational messages just contribute to our sense of overwhelm?

A Love-Hate Relationship

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

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

Prior to discovering she could adjust the settings, her smartwatch repeatedly informed her she was not being productive enough. Now, the watch frequently reports her she's had a bad night's sleep.

"I've got a infant, I don't need to be informed I've not slept," she says. "I know that all too clearly."

Why doesn't she just take it off?

"I suppose I could, perhaps, but I have this love-hate relationship with it," she continues. "I love it for its exercise data, but I'm unsure whether the additional features it can now do is maybe too much for me."

The Technology Behind the Tracking

Every device of smartwatch has its own novel way of measuring your bodily functions and interpreting your data, but the most use detectors on the reverse of the watch.

They usually shine small, green LED lights onto your skin which can detect blood flow, detecting your BPM. Higher-end devices analyse changes in the electrical current that runs through the skin to assess your recovery state.

A Fine Balance

A professor says that for most people for smartwatches, it's a "delicate equilibrium" - 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 "anxious healthy".

He points out that the most advanced wearables can perform tests like heart rhythm analysis, which regularly monitor how normal the heart is. They can flag if someone is experiencing a heart arrhythmia, where there is irregular signals in the heart causing an uneven pulse.

This does not mean someone is imminently going to suffer a heart attack, but it can give an early warning they might be more susceptible of a heart problem in the future.

But how to understand these readings is complex. The expert fears that as more functions are incorporated, people may find it hard to fully comprehend their data.

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

A clinical psychologist specialising in cardiology agrees. Research into the effect of wearable tech on a specific group of cardiovascular patients suggested a significant portion of those who were given devices to monitor their condition experienced greater stress and were "had a higher tendency to use doctor's time".

She noted a vicious circle with her patients - they noticed a alarming metric on their watch. They felt anxious. Their heart rate increased. They got more worried. They re-examined the data, and their anxiety increased again.

"If we see data about ourselves that we can't properly interpret then, understandably, we are going to become concerned," the psychologist says. "We look, we re-check - it becomes a feedback loop."