Enhance your triathlon experience by pairing hrm tri with your forerunner 920xt1 the hrm tri stores heart rate data when underwater then forwards it to the 920xt our smallest and lightest module fits within the width of the strap its soft rounded edges and covered seams make the strap super comfortable out of the water too running dynamics hrm tri also has an accelerometer in the module that measures torso movement to calculate 3 running metrics2 cadence the number of steps per m