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Fitness trackers: How to best use them for optimal results

How much should you depend on data from fitness devices?

More people are now working out regularly, eating clean and taking conscious charge of their health.

Many are also turning to fitness trackers which provide objective and measurable data to keep track of their progress.

Brands such as Fitbit, Garmin, Polar and Apple offer fitness trackers and related wearable technologies.

From basic step tracking to heart rate monitoring, GPS, calorie tracking and sleep monitoring, no matter how simple or demanding your fitness needs may be, there is a device for you.

But exactly how reliable or accurate is the data?

Should you be religiously modulating your lifestyle based on it?

Here are several factors to note when considering fitness trackers.

Get walking

Multiple studies have shown high validity for step tracking.

The number of steps you take in a day can be a good reflection of how sedentary you are, which in turn can affect your health.

The more steps you take, the higher your non-exercise activity thermogenesis (Neat), which is the amount of energy you expend through your regular daily activities of living.

A useful way to make use of this might be to monitor the usual number of steps you take in a day and then add an additional but attainable goal of 2,000 to 3,000 more steps.

You may be surprised, but a leisurely stroll around a large mall may easily attain those additional thousands of steps.

Don't "eat back" the calories you have expended

Research suggests that the energy expenditure data from your fitness tracker is likely to be inaccurate.

A systematic review and meta-analysis by researchers from the University of Leeds looked at data from 60 existing studies involving 40 different fitness trackers.

They found that energy expenditure measurements vary vastly between devices, with a sizeable margin of error - either over- or under-estimating calories expended, depending on the device and activity involved.

Devices that used a heart rate monitoring function to compute energy expenditure tended to be more accurate than those without.

For those looking to lose weight, it may be more useful to look at your trend in energy expenditure.

The accuracy of heart rate monitoring is device-dependent

Most devices use photoplethysmography (PPG) for heart rate measurement. The pulse signal on your wrist can be detected using a light source and a light sensor on your fitness tracker.

Unfortunately, the accuracy of heart rate monitoring can be affected by motion that affects the contact between your skin and your fitness watch - for instance, during high intensity exercise - which ironically, means your tracker may be unable to record your heart rate when it matters the most to you.

The accuracy of heart rate monitoring is also highly device-dependent from comparison studies.

It is also important to note that while your fitness tracker's heart rate monitoring function can be useful as a rough guide to your exercise intensity, you should not excessively fixate on the numbers shown.

Don't fret too much about your sleep

Sleep is extremely complex and formal sleep studies take into account multiple physiological parameters including brain wave activity, eye movement, muscle movement and breathing.

Many fitness trackers utilise an accelerometer (which detects arm movement) to measure sleep. With these devices, a lack of movement can often be misinterpreted as time spent asleep.

Your fitness tracker may be useful in giving you a rough gauge of your sleep habits but individuals who suspect they may suffer from sleep issues should look to a more formal sleep study.

The writer is a doctor at DTAP Clinic Robertson.