What's the best interval running workout?

Ive been packin on muscle for a few years now, and i want a hard 6 pack before the end of this summer, before my senior year. Iv'e been doing lots of cardio lately (swimming running) and still lifting weights, with lots of circuit training. Whats a HARDCORE...

I'm 19, 158 pounds 6'0 and i have a high metabolism. I want to get some fat off me since I still got some on me that has been covering my abs. I do workout and workout my abs and i'm eating pretty healthy and now avoiding all fatty foods. I havn't been...

Just trying to lose 10 pounds, I only weigh 115 at 5"5... but want to get down to 105, whats a great fat burning workout besides running, etc? Or combination of workouts? Any ...show more

Okay ive been running every morning for a while now with my ipod...but the regular music i usualy listen to isnt good for workout music....so whats some good workout songs? i need a ...show more

I'm getting knee pains on the front of my knee after i run. I'm not really used to running and i was running on cement. It hurts really badly when I kneel down.It's been hurting for about 1 week. I workout everyday and i was thinking if i should stop...

first im 13 year old teenage boy ... - I was just outside doing my normal workout and I was doing my running first and when I was running , I hit my ankle on a hard metal tool , that my dads using 2 fix the truck with. Then my ankle started bleeding...

This happened after running 6 miles and rowing on a machine for about 6.5 miles. I've just started rowing again with my school's team and we had the above workout out last saturday (first week Id been back working out). I've never run 6miles before and...

Ok so I'm running between 5-10 miles a day at the moment, I wear the mizuno wave rider 10's I've had them for too long now, the weight of the shoe is too heavy as well. I'd like a lighweight running shoe that has the cushion aswell, without breaking...