The Struggle for Accurate Measurements on Your Wrist

Until recently, I didn’t know a thing about how my roughly 25-minute bike commute across San Francisco - or any other part of my day, really - affects my body, other than that I inevitably arrive at work sweaty and a bit out of breath when I’m in a big rush. How high is my heart rate? Do my sleep habits affect it? How many calories do I burn?©2015 Massachusetts Institute of Technology (P)2015 Audible, Inc.