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A Cardiologist’s Perspective on Wearable Technology

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A Cardiologist’s Perspective on Wearable Technology

Wearable technology that includes tracking information relating to health and fitness is becoming increasingly popular. In fact, about 48 percent of Americans rely on wearables, such as FitBits, Apple® Watches and others, to measure and track fitness. What exactly makes wearables a worthy choice for monitoring fitness? Cooper Clinic’s Nina Radford, MD, explains the functionality, accuracy and other factors that play into the effectiveness of wearables.

What are the main functions of wearables?

For most, wearable devices are most commonly used to track and monitor fitness variables such as distance traveled, activity patterns, steps taken, calories consumed and heart rate. Some wearables also measure sleep patterns by tracking movement during sleep.   

There is a great deal of discussion about the potential of wearable technology to improve the delivery of health care. This potential has been realized for example with smart phone applications that can detect abnormal heart rhythms such as atrial fibrillation which may occur intermittently. Patients with chronic diseases such as heart failure may be able to monitor their heart function at home and be alerted when they need to contact their health care providers concerning important changes in heart function measurements that may not yet be causing symptoms. “In this way, treatment recommendations could be made early when subtle changes in monitoring are first detected. This might allow us to avoid some hospitalizations altogether,” says Dr. Radford. Though the use of wearables for monitoring health conditions is in its early phases, Dr. Radford sees it becoming a more prominent and common function in the future.

Are wearables accurate?

The accuracy of data from wearables has been the focus of a number of recent scientific studies. Several studies have demonstrated that step count estimates for most wearables were generally reliable (within 4–6 percent of the reference) with both over-estimation and under-estimation reported.

Because heart rate ranges for exercise are often provided to patients with various cardiac conditions, the accuracy of the heart rate measurements have come under fire recently. 

  • In one study* of 50 volunteers testing five heart rate wrist monitors against a Polar® chest monitor, using a treadmill protocol, the monitors were reasonably accurate measuring heart rate with the average percentage errors ranging from about 1-10 percent depending on the device and the walking or running speed.
  • In another recent study* from Cleveland Clinic investigators, using EKGs to track heart rate, in 50 volunteers using four heart rate wrist monitors and a Polar® chest monitor, the chest strap monitor was the most reliable. The wrist monitors values were off by an average of about 30 beats (higher or lower).

In general, the accuracy of the wrist monitors was best at rest and diminished with exercise. These authors recommended that these devices be used recreationally but should not be used to monitor heart rate in cardiac patients who may need to keep their heart rates in a very specific range during exercise.

  • Small studies** have shown that, in general, when it comes to measuring calorie burn, a number of wearables are not very accurate.
  • In another recent study, researchers confirmed that in general, energy expenditure increased as a person shifted from walking to running (as expected). However, the measurement of calorie burn with wearables showed wide variations compared to reference values.

“This type of technology is not quite ready for precise calculations of calorie expenditure integrated into a weight loss program for example,” explains Dr. Radford. “Take your calorie burn display with a grain of salt when you use a wearable.”

Do wearables make people healthier?

In September 2016, JAMA published the results of a study assessing the impact of wearable technology in overweight and obese participants (young adults) engaged in a weight loss program. All participants were put on a low-calorie diet, prescribed a specific level of physical activity and provided counseling sessions for six months. After six months, participants were to track their food, activity and other information through a web portal or wearable technology (an upper arm band that tracked activity and energy expenditure) with web support. Surprisingly, after two years of following these participants, the addition of wearable technology resulted in less weight loss compared to the web-only group. 

“Although this single study doesn’t show a significant relationship between wearable technology and weight loss, there is good research showing most people are more active when they count their steps,” says Dr. Radford. “An older meta-analysis of 26 studies (done when people wore pedometers clipped to their waist) showed that overall, pedometer users increased their physical activity by 26.9 percent over baseline and this was associated with a modest amount of weight loss.” Fine tuning must be done in order to use wearable technology to help people lose weight.

Is my health information kept private?

It is important to be an educated consumer about the privacy of your data when purchasing and using internet-based wearable technology. In the past, there has been a great deal of concern about the use of unlimited tracking of data by third party vendors. Now, these technology companies have become much more transparent about how your fitness data is stored, managed and shared as well as how you can opt out of giving third party vendors access to your de-identified data.

“When you download a health app or use a wearable, you need to pay attention to the privacy policy of that company,” explains Dr. Radford. “Review your privacy settings on your smart phones and computers so you know what health data you are sharing.” 

Which type of wearable is best?

When choosing a wearable, Dr. Radford’s advice is to purchase one that is not so complicated that you put it in a drawer and never use it. “Some people can be overwhelmed by too many options or functions on a wearable device, especially if they are new to monitoring their health and fitness,” she says. “Other people love the idea that they can look at a text, track their activity and follow the news on a single device the size of a silver dollar.” 

“If you are not sure whether you will like a wearable, start out with something simple that measures steps and distance,” explains Dr. Radford. “If you want to upgrade to a more sophisticated device, you will have plenty of choices.  Innovation is the name of the game with wearable technology so there will always be a newer model on the horizon.”

What is a physician’s overall perspective?

Wearable technology has a lot to offer. “So often I hear my patients tell me they don’t engage in a formal exercise program but they are running around all day. I challenge them to actually measure their steps. People are often surprised by how sedentary they really are,” says Dr. Radford. “Once they start to track their steps, they realize they need to make a plan to fit in physical activity every the day. While getting 10,000 steps is great, any exercise is better than none. So I consider 5,000 steps a victory in a former couch potato!”

For more information about services provided at Cooper Clinic, visit or call 972.560.2667.

Article provided by Cooper Aerobics Marketing and Communications

*Sarah E Stahl, Hyun-Sung An, Danae M Dinkel, John M Noble, Jung-Min Lee
How accurate are the wrist-based heart rate monitors during walking and running activities? Are they accurate enough? BMJ Open Sport Exerc Med 2016;2:1 e000106 doi:10.1136/bmjsem-2015-000106

*Case MA, Burwick HA, Volpp KG, Patel MS. Accuracy of Smartphone Applications and Wearable Devices for Tracking Physical Activity Data. JAMA. 2015;313(6):625-626. doi:10.1001/jama.2014.17841.

**Int J Behav Nutr Phys Act. 2015 Dec 18;12:159. doi: 10.1186/s12966-015-0314-1.
Systematic review of the validity and reliability of consumer-wearable activity trackers. Evenson KR1,2, Goto MM3, Furberg RD4.

**Kaewkannate K1, Kim S2. A comparison of wearable fitness devices. BMC Public Health. 2016 May 24;16:433. doi: 10.1186/s12889-016-3059-0.