Your Garmin device uses extended physiological metrics to help you get the most out of your workouts and feel confident about what you can accomplish when you toe the line. Once the watch learns your lactate threshold estimate, you can apply it to your heart rate training when setting up zones. Overall training load, sleep, nutrition and general life stress play a role in how you will perform in a tough workout. Watch Joe from Garmin as he shows you how your Garmin device takes away the guess work by detecting your lactate threshold for you.
Learn more about the Forerunner 935 here: https://buy.garmin.com/en-US/US/p/564291