The RS400sd adds in running speed pace and distance with the S1 foot pod so the active runner who runs multiple events each year can monitor all elements affecting performance. The Running Index feature will help the athlete to improve their running efficiency which in turn indicates an improvement in their economy of running performance. Innovative heart-rate-monitor watch designed for avid runners. Includes foot pod that attaches comfortably to running shoe laces. Accurately and wirelessly measures speed distance pace and performance. Visual and audible target zone alarms syncs with Polar Pro Trainer 5 software. Comes with Polar T31 coded HR transmitter belt. Records 99 exercise files.