What is the difference in speed etc in these three types of exercise? I would love to start running. I usually do sprints 3 times per week, it is hard but I do it. However if I try to run or jog at a steady pace I can't even make it around the track once without getting too winded, and my heartrate flys. What is going on?? I need to know how far to start with at what pace. Also I walk about a 15 minute mile when walking outside. I don't know if that is a good pace or not.