10/31/2019 How do they work? + a SPOOKY TRUTH ABOUT YOUR HEALTH Smartwatches and Tracking Your Heart Rate during a workout. Rhett Turner, M.A., ACE-CPT, USAW-SPL1 With a staggering 25% of adults not meeting recommended guidelines for physical activity, physical inactivity has been identified as the fourth leading cause of human mortality (Murakami et al.,