How Accurate is Your Wearable Technology?

How Accurate is Your Wearable Technology?

Ask any decent PT or gym instructor about what is essential to getting the most of your workout and they will tell that accurate feedback of the intensity of your programme is one of the most important measurables. In order to assess how much benefit you are getting you need to track your workload.

These days of course this is made easier by the variety of fitness trackers, wearable technology which can link in to the apps and the cloud so you can get feedback whenever you are connected to the internet. It can even add in the motivation of comparing your effort with friends or workout buddies. Wearable technology is perfectly placed to allow you to compete with friends and to share your workouts for fun and encouragement. Social sharing, gym leaderboards, and a workout community can all add real power to the motivational forces that keep you exercising on a regular basis.

But have you ever wondered whether these fitness tracker devices are accurate?

We asked Michelle Read, our Gym Manager, to investigate what research was out there testing the advice. She found a recent study published in this month’s edition of Science Daily which was conducted by researchers working for the American College of Cardiology in Cleveland, USA. They compared the accuracy of five popular wrist-worn fitness trackers with that of the traditional old-fashioned chest strap monitor. They measured the performance across several types of exercise and intensity levels. Based on their findings, the old-fashioned chest strap monitor is best, particularly for people who need to keep tabs on how quickly or slowly their heart is beating during activity. The standard chest strap was the most accurate regardless of the intensity of the workout or whether someone was using the treadmill, elliptical or stationery bike. 

The research was conducted on campus with 50 volunteers. Each participant was fitted with a continuous 4-lead electrocardiogram (EKG), a chest monitor and an armband. They were then randomly fitted with two of four different wearable heart rate monitors (one on each wrist). The devices chosen for testing (Apple Watch, Fitbit Blaze, Garmin Forerunner 235, and TomTom Spark Cardio) were based on their popularity and sales figures. Researchers then recorded volunteers' heart rates at rest and after light, moderate and vigorous exercise across three types of activities, including the treadmill, stationary bike and elliptical. Measurements on the wearable devices were compared to readings from the chest strap and EKG. 

The chest strap monitor closely matched readings from the electrocardiogram (EKG), which is the gold standard for measuring the heart's activity. However, the wrist-worn devices were less accurate on average. While the watch-style heart rate monitors may accurately report heart rate at rest, and most were acceptable on the treadmill, they were fairly inaccurate while bicycling or using the elliptical. Of the wrist-worn heart rate monitors, only the Apple Watch provided accurate heart rate readings when participants switched to the elliptical trainer without arm levers; none gave correct measurements when they used arm levers. The wrist and forearm monitors also became less accurate the more intense the activity levels, with the exception of the Apple Watch.

What's behind the discrepancies? Unlike the chest strap, which like the EKG measures electrical activity of the heart, wrist-worn monitors use optical sensing or light to measure blood flow.

"It's not measuring what the heart does, but rather blood flow -- basically the volume of blood in the tissue," said Marc Gillinov, MD, The Judith Dion Pyle Chair in Heart Valve Research, Thoracic and Cardiovascular Surgery at the Cleveland Clinic, Ohio and the study's lead author. Gillinov said, adding that these devices also introduce many more variables that can result in incorrect readings. Such variables include insufficient contact with the skin because of sweating or poor fit, or skin pigmentation.

Our own Michelle Read commented that “this study is limited due to its small size but it is very current and it does correlate with a number of other research studies I’ve found. What is really encouraging is that this study points to the value of using the myZone technology that we use as standard in our gym. The myZone uses a chest strap belt to track every ounce of effort you put into exercise by your heartbeat. This data is then used in a very simple point system, called MEPS (MYZONE Effort Points), to give members a sense of satisfaction and achievement. It ensures all of your effort is rewarded. The accuracy of recording your heart rate is therefore of paramount importance and it is great to know that we are using the most accurate technology.”

We have over 100 members using the myZone technology so feel free to ask a member of the gym team if you want to learn about the benefits such technology can offer to your programme.