Each year, the American College of Sports Medicine surveys fitness professionals around the world to identify the hottest trends in the industry. In 2016, for the second year in a row, activity trackers were the number one response. In fact, the annual sales of activity trackers doubled from 2014 to 2015, to over $1.46 billion, and Apple sold more than 18 million apple watches in 2017 alone. That one device counts for over one half of the smart watch market. In 2018, with the products being around for a few years, wearable technology is still number three on the top trends list. With such a massive amount of growth, and the devices appearing everywhere, we could all be well served by a look at the pros and cons.

The number one benefit most cite from activity trackers is a motivation to move more. When we are tracking our steps, it can become a very beneficial challenge to try and add more each day. Anything that encourages us to move more, be more active and burn more calories has the potential for a major impact on our overall fitness and health level.

The primary drawback, at this stage of technological advancement, is accuracy. An Apple watch or a wrist worn tracker without a torso strap and transmitter rely on an optical sensor to estimate Beats Per Minute. These devices have been found to be substantially less accurate than devices with straps, especially at higher levels of exertion. In fact, there is now class action litigation (image above) against manufacturers of wrist monitors from deaths claimed to result from wearers reaching heart rates that were too high but being unaware because the device showed them to be at a much lower rate. This shortcoming would also underestimate your calorie burn as well.

In a study done by the Cleveland Clinic, it was determined that watch-like wristbands that monitor heart rate may not offer true readings during exercise. “All worked pretty well at rest,” said Dr. Marc Gillinov, the Cleveland Clinic cardiac surgeon who led the experiment. “But as people exercised, the accuracy diminished.” Dr. Mitesh Patel is an assistant professor of medicine at the University of Pennsylvania’s Perelman School of Medicine in Philadelphia.” An electrocardiogram records the heart’s electrical activity. It’s the “gold standard” for measuring heart rate”, Gillinov said. “A chest strap, which also monitors electrical activity, is just as accurate, he added.”

Apple’s own support page includes the following information as to why your heart rate feedback may not be accurate;

“Many factors can affect the performance of the Apple Watch heart rate sensor. Skin perfusion (or how much blood flows through your skin) is one factor. Skin perfusion varies significantly from person to person and can also be impacted by the environment. If you’re exercising in the cold, for example, the skin perfusion in your wrist might be too low for the heart rate sensor to get a reading.

Permanent or temporary changes to your skin, such as some tattoos, can also impact heart rate sensor performance. The ink, pattern, and saturation of some tattoos can block light from the sensor, making it difficult to get reliable readings.

Motion is another factor that can affect the heart rate sensor. Rhythmic movements, such as running or cycling, give better results compared to irregular movements, like tennis or boxing. If you’re not able to get a consistent reading because of any of these factors, you can connect your Apple Watch wirelessly to external heart rate monitors such as Bluetooth chest straps

The second inaccuracy issue comes from steps being calculated by arm movement with many devices. A client using a battle rope, for example, can show adding 100’s of steps without ever moving from their tracks. Even riding on a bumpy road can add steps you didn’t take to your tally, giving you the impression that you’ve worked more than you actually have.

In conclusion, if you need or desire accurate heart rate feedback, a device with a chest strap and transmitter is the most accurate and safe, and your best bet. If you are only looking for something that may entice you to be more active, a wrist only wearable may very well be sufficient. As quickly as technology is changing, this topic may very well have new answers soon.