is there a difference between jogging for 30 min or walking at a steady pace and a incline if your heart rate is the same during the 30 min? Example, today I walked at a 10 degree incline at 4.0 mph and my heart rate stayed between 130 and 138 for 30 min. Yesterday I jogged at 4.4 - 0 degree incline for 30 min and my heart rate was in the same zone. Whats the difference?