Get up to 31 days when smartwatch mode is enabled or up to 58 hours in GPS mode on the 51mm editions. Variable light intensities and a red safety light give you greater awareness while you train in the dark and can provide convenient illumination when you need it. Endurance score measures your ability to sustain prolonged efforts and combines training data from all your athletic pursuits to help you understand how training impacts your overall endurance. Use preloaded activity profiles to get data and insight from your active pursuits. A new heart rate sensor is designed to give you optimised performance in whatever sport you're doing.