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.

bump,bump, bump

A 15-min walking mile is a leisurely pace - it's exercise, but it's not vigorous or anything. As for jogging, go at a speed that you feel comfortable running at the very least for five minutes. Then, build up. Or, if that's tough, run as long as you can, then walk, then run the moment you have the energy, etc., until you can run at a good pace for several minutes.

What's your sprint workout?

Here is my HIIT workout--- 5 minute warmup, 30 second on, 60 seconds off sprints as hard as I can, for about 8-10 sprints, 5 minute cooldown.

Also you think that a 15 minute mile is not a good time? What is? I feel like I am walking pretty fast, I am 5 ft 3. I get my heartrate up pretty good doing this.

Your HIIT and sprints looks good to me. I'm guessing that each sprint is maybe 100m? Even if it's less, that would be a good workout.

As for a good time for a walking mile, I honestly don't know. The only reason I know the 15 minute mark is because during miles for school, I've had friends who walked (because they already got times; they were quite athletic so I don't know how that affects you) and made it in about 15 minutes. However, you shouldn't be focusing on that - rather, focus on improving your own time and try to work on jogging too.

For 5ft 3, 15 minute mile(4mph) is quite brisk I think.

What do you mean by "for 5ft 3"? I don't think that endurance or speed in any real distance has much to do with height.

Taller people will have a faster normal walking speed I guess. I find it hard to walk faster than 4.8mph on the treadmill beyond which I cannot walk comfortably and have to start running. So would'n it depend on how long the legs are?

Of course, under maximal effort I agree that it does not make a difference.

Thanks for all the great replies. I feel better now~