Wearable technology is getting a lot of attention these days and for good reason. These devices are becoming increasingly more integrated into our daily lives and are providing new insights into our personal activity and fitness levels. According to IDC Research, the worldwide wearables market will reach 45.7 million units shipped by the end of 2015 and 126.1 million units in 2019, indicating a compound annual growth rate over 45%.
To date, the vast majority of that growth has been in basic activity trackers like the Fitbit One and the Jawbone UP that use an accelerometer to measure movement and translate those measurements into estimates of step counts, calories burned, distance travelled and other metrics. However, these devices won't tell you how your body responded to that movement. In other words, while an activity tracker can estimate that you've taken 10,000 steps in a day, it can't tell you how hard your body worked to take those 10,000 steps or how your body recovered from that effort. Measurements of both physical activity and the body's response to physical activity are critical components in determining whether you're actually improving your health and fitness.
This can be explained by what exercise scientists refer to as workload. Workload is defined as the amount of time spent doing an activity or workout multiplied by the intensity of that activity. For example, to burn approximately 400 calories you can workout for an hour at low intensity or workout for 20 minutes at very high intensity. This may seem obvious, but while basic activity trackers can be good at measuring how many steps you've taken, they are incapable of telling you how your body actually responded to those steps. Half the equation is missing with basic activity trackers, since they are only measuring activity and time, not your body's response to that activity. The best way to complete that equation and quantify your body's true response to workload is by continuously and accurately measuring heart rate.
With accurate information about your workloads and level of effort you are on your way to getting much better insight into your health and fitness. For example, with training you will start to see improvements in your cardiac efficiency. Efficiency in any system is the ratio of the energy delivered by a system to the energy supplied to it, so cardiac efficiency essentially measures how efficiently your heart can turn energy into work. Like any muscle, the heart and cardiovascular system grow stronger and more efficient with exercise, so as you get in better shape your body is able to produce the same amount of work for less beats from your heart. Though not as accurate, this is why people measure their resting heart rate as a proxy for cardiac efficiency, because it tells you how hard your heart is working (beats per minute) to achieve the same amount of work (during rest). The same analysis can be applied to cardiac efficiency during workouts, so if you complete the same exercise once a month and measure your average heart rate during the workout, you will start to see your average heart rate go down over time if you are getting more fit.
There are many other metrics that can be generated from accurate biometric sensors including maximal oxygen consumption (VO2max) for cardiovascular fitness measurement, heart rate recovery, heart rate variability for monitoring training levels and stress, blood pressure, and breathing rate. This is why more companies are adding continuous heart rate monitoring to their next-gen wearable products. You can expect to see this trend continue as consumers get more value from the powerful insights that accurate heart rate data can provide.