Modern wrist-worn activity trackers like the Garmin Vivomove do way more than just measure steps, they monitor sleep patterns, too – providing a more holistic view of one's health than just recording how far you walked. But how do they work? And what kind of insights can we reasonably expect to get out of them? Here's the low-down on the tech behind sleep trackers and how they can help you get a good night's rest.

We all know instinctively that sleep's important. It helps the body rejuvenate, preparing it for the next day's bout of urban madness. Just as importantly, it clears the brain of accumulated waste and is critical for memory consolidation. No wonder we're cranky as hell when we don't get enough. Sadly, modern pressures cause many of us to ignore this most basic biological constraint. There just never seems to be enough time in the day to get everything done. So we knock back more caffeine, pick our weary heads up and keep on going. It's called survival.

What happens when you can't sleep?
The thing is, missing out on your beauty sleep has serious health ramifications. Even one bad night of tossing and turning can cause reaction times to slow down and critical lapses of attention to occur. It's also when the urge to snap at loved ones is strongest. It gets worse: Many cognitive functions, including working memory, mental arithmetic, reasoning, creative thinking and verbal fluency suffer, too.

String a few sleepless nights together, and the severity of these mental impairments increase significantly. The end result is something we can all do without – more stress. And, once stressed, it's frustratingly difficult to get any sleep. You know the drill. It becomes a vicious cycle that, unless taken seriously and managed, can spiral out of control and become the catalyst for an onset of depression, heart disease, high blood pressure, a weakened immune system, stomach issues and more.

Clearly, what's needed is for us to elevate the importance of sleep to that of the other two established health pillars; proper nutrition and regular exercise. Fortunately, wrist-worn sleep trackers allow us to do just that. But, to understand how we can benefit by using them and what their limitations are, we need to first check out how specialist sleep clinics go about gathering their data.

How the pros measure sleep
The scientific study of sleep, or polysomnography (PSG) typically requires the sleep-deprived to grab their pillows and spend a night or two in a sleep lab hooked up to a rats nest of around 20 wires. A number of physical activities are monitored throughout the night to track your sleep cycle, including:
• Brain waves (EEG)
• Oxygens in your blood
• Airflow in and out of your lungs as you breath
• Breathing effort and rate
• Body position and movement
• Heart rate and rhythm
• Eye movement
• Electric activity of the muscles

Without a doubt, polysomnography delivers accurate, science-based results. That said, this respected clinical approach does have some issues. Here's why: Collecting the data requires test subjects to leave the familiarity of their home environments and get into strange bed – an activity in itself that's not exactly conducive to a good nights rest. And, as many sleep disturbances are environmentally related (too much light in the bedroom, for example), the PSG test basically messes with the experiment because the subject's sleeping conditions have changed. Added to that, subjects are literally tied down by monitoring equipment, so some level of disturbance throughout the night is inevitable.

To get around these drawbacks, sleep specialists have been providing test subjects with professional-grade wrist-worn sleep trackers for about 30 years. The rational being people can wear them in the familiar comfort of their own homes for a week or two – providing specialists with more natural insights into their sleep patterns than can be ascertained by spending just one or two nights in a clinic.

How wrist-worn sleep trackers work
Instead of relying on high-tech medical gear, wrist-worn sleep trackers use actigraphy. This method incorporates an accelerometer to track movement, then uses algorithms to extrapolate the data and make sense of it all. How they work is simple. Basically, movement equals wakefulness and prolonged lack of movement equals sleep.

Understandably, these sleep trackers are incapable of providing the detailed insights achieved when undergoing PSG testing in a sleep clinic. For starters, as they can't track eye movement, it's impossible for them to register the REM (dreaming) periods of your sleep cycle. (To get around this many trackers simply incorporate REM intervals into the “deep sleep” category on their smartphone app-based graphs.) And, as their tech is accelerometer based and reliant on movement, they can be fooled into thinking you're asleep when, in fact, you're just sitting quietly reading a book in bed.

That said, wrist-worn sleep trackers provide more than enough info for those wanting to monitor their sleep patterns in the real world.

My experience is only anecdotal, but I found the sleep monitor on Garmin's Vivomove activity tracker to be surprisingly accurate. How it manages to differentiate between light and deep sleep periods, I have no idea (no-one does – it's a closely guarded trade secret), but it does. What I saw every morning when checking out the sleep graph on my smartphone app corresponded with exactly how I felt. And, after I'd been wearing it for a week, an interesting pattern began to emerge that I found really insightful.

Another area where it was particularly strong was its ability to track movement throughout the night, letting me know if I'd slept restlessly or not. Plus when it indicated I was awake, I was – even if I did have to think a bit before remembering the neighbour's dog barking at 3 am.

For someone like me who doesn't have any serious health issues, using a wrist-worn sleep monitor to track sleeping patterns proved to be ideal. How much sleep did I really get? Did it include the necessary mix of light and deep sleep periods, and how long were they? Was it a restless night, or did I sleep like a log? It told me all I needed to know. And, by simply making me aware of how well or not I'd slept, wearing it made me take bedtime more seriously – which can only be a good thing.  – (c) 2016 NavWorld