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Wrist worn fitness trackers (smart watches) and chest strap heart rate monitors have experienced astronomical popularity in the recent years. This is mainly because of the plethora of fitness monitoring features they have to offer and also a growing population of health conscious individuals who are making sense of the data presented to them. However, research has shown that wrist worn fitness trackers might not be the best way to measure heart rates as compared to chest strapped heart rate montiors due to the way it measures our heart rates. Wrist worn trackers tend to slightly underestimate heart rate values and the accuracy of measurement reduces during the course of exercise (1). Here we will discuss more pertaining to the differences between heart rate sensors and smart watches in measuring our heart rates and talk about ways to better don smart watches for better accuracy during exercise or through out our normal daily activities.
Heart rate strap sensors VS wrist worn fitness trackers
Chest strap sensors function the same way as an electrocardiogram (EKG), heart rate is being recorded via detecting the electric pulses transmitted by the heart when it beats (1).
Wrist worn fitness trackers operate with optical heart rate sensors, these sensors work by shining an LED directly onto your skin and monitors the manner with which that light reflects off your blood vessels. Sensors in your fitness tracker will then pick up the information and process it into a pulse reading format (2). There are a number of factors that can skew this data gathered. Some of them include the color of your skin, how much hair you have on your wrist, and how tightly you’re wearing your tracker. All these can potentially affect those resting and active heart rate values.
How to get more accurate results from smart watches?
Some ways to further improve the accuracy of wrist wearables include :
1. Keep the watch snug - not too loose or tight on the wrist.
This is especially important for heart rate sensor accuracy. Try to tightly strap your watch to your wrist so it doesn’t move, but not so much that it becomes uncomfortable. Too tight will cause blood flow restriction and too loose will result in skin contact reduction with the sensor (2).
2. Position on the wrist
During daily wear, it can be worn about 1 finger distance away from the wrist bone.
During exercise, it is advisable to wear it about 2 fingers distance away from the wrist bone. This is because when executing some exercises and movements such as push ups, weight lifting or any exercise that might require you to bend your wrist at an angle, this might result in some blood flow cutting off closer to the wrist. As such, moving the watch further away from the wrist gives the sensors an opportunity to measure blood flow more accurately (3).
3. Keep the sensors clean
You can either wipe down the sensors or wash them periodically so that the sweat residues do not clog the sensors, which might in turn result in inaccurate readings.
4. Update Software
Keep the watch and app software updated for more accurate measurement algorithms and interface.
Wrist smart watches are suitable for recreational purposes where is gives a rough indication of the heart rate and guide to improve fitness levels through heart rate zoning. However, for patients who require special attention to their heart rate monitoring, a chest worn heart rate monitor might be a better choice, but this will have to be left entirely to the medical professionals to decide (1).
By : Alvin Ho
B (Eng), MBA, Certified Allied Healthcare/Fitness Professional (EIMS), Master Fitness Trainer / Fitness Nutrition, Resistance & Endurance Training Specialist (NFPT)