A constant personal trainer at your side, the 620 tracks it all. It can calculate your maximum oxygen consumption that pushes you to constantly improved performance levels. When used in conjunction with a heart rate monitor, the 620 sets to work measuring speed, beats per minute, and race time predictions. Similar to the 630, it can give you goals for your next run or race based on your above data. Aside from helping you meet your goals, it tells you when you need to rest based on your personal physiological data, so you can get the best out of your training. It boasts up to 6 weeks battery life when doing average daily workouts, or 10 hours battery life in solid training mode.