One of the best long distance running watches especially for 100K races. Previously, my other GPS watches only lasted anywhere from three to six hours; good for a marathon, but not so good for ultra marathons from seven to 14 hours.




20-hour GPS + heart rate detection super horse-class endurance. VO2 Max maximum oxygen uptake detection. High/tilt detection. Multiple training mode. 24-hour all-weather activity measurement. Five-segment exercise intensity reminder. RUNSENSE View Cloud Diary/Action App. Quasi-zenith satellite. GPS positioning per second. Double heart rate sensing, the error is within ±2% compared to the heartbeat band. Japanese Seiko technology.

  • Unique: GPS + heart rate detection + 20 hours of battery
  • Wide: VO2Max maximal oxygen uptake detection
  • Height/slope detection
  • Multiple training mode
  • 24-hour all-weather activity measurement
  • Five-stage exercise intensity reminder
  • RUNSENSE View Cloud Diary / Action APP
  • Standard: Quasi-Zenith Satellite System
  • GPS position per second
  • Double heart rate sensing, within ±2% compared to the heartbeat band


The Epson SF-850 was one of the first sports watch that offered long-battery usage plus a combination of features useful for long-distance runners such as GPS, heart rate monitor, VO2max, distance, altitude, and speed.

Asides from the plethora of features, I really like the fit and feel of the watch during exercise. While wearing the watch during runs, bikes, and swims, the weight was light and movement unencumbered. The feel of the band design was comfortable without the annoying feeling being too hot or tight. The display was easy to read and easy to change by tapping on the screen.

Moreover, uploading the activity data and the GPS routes is convenient. A dashboard display from a mobile device or online website shows daily activities such as heart rate charts, speed, maps, sports, and sleep. Overall, I have had this watch for several years and it is still my number one sports watch. This design also provides features for bicyclists, walkers, hikers, and fitness enthusiasts.

For use with Epson® Runsense

Voracity Sports is designed to interact with Epson® data to provide an activities picture. We do this in order to gauge fitness levels and to recommend improvements.


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