sprint your ass off--literally

so one of the hardest treadmill work outs i have ever done is this 20ish minute sprint work out.  i wouldn't recommend it to a beginner although it could be tweaked a little bit to make it possible. it's a lot easier for me to post hard work outs when i know that i can't do them so i won't be suffering.  so this is what this ass kicking work out is all about:

• start out at a flat grade on the treadmill walk/run for about 3 minutes to get your muscles warmed up.  i would recommend running at least half of it so your muscles don't go into shock when you start sprinting.  you can lengthen the warm up if you have the time and feel more comfortable that way
• after your warm up, you're going to do intervals of 30 second incline sprints and 1 minute walking breaks
• if you have two available treadmills, it's a little less of a hassle to use one for your break period and one for the sprints but i know that's not going to be the case in most gyms
• sprint #1 - 30 seconds at 1.0% grade and at least an 8 mph speed
• your speed is definitely going to be determined on what type of shape you're in.  if you work out on a regular basis and include some type of running or more intense cardio you should be able to do at the speeds i recommend if you really want to push yourself
• you're going to increase your speed as you increase your incline as well which is why i recommend starting around 8 mph for those bad asses out there that are thinking "this work out is for wussy's". suck it trebek
• walk for 1 minute at 0% between 3 and 4 mph
• sprint #2 - 30 sec. at 3.0% grade 8.5 mph
• walk
• sprint #3 - 30 sec. at 5.0% grade at 9 mph
• walk
• sprint #4 - 30 sec. 7.0% grade at 9.5 mph
• walk
• sprint #5 10.0% grade at 10 mph or the highest speed you're able to go without feeling like you're going to fall off
• walk
• sprint #6 - 30 sec. 7.0% at 9.5 mph
• walk
• sprint #7 - 30 sec. 5.0% at 9 mph
• walk
• sprint #8 - 30 sec. 3.0% at 8.5 mph
• walk
• sprint #9 - 30 sec 1.0% at 8 mph
• at the end i usually run at a steady pace for a minute or 2 and walk for a total recovery time of 5 minutes. 
• once again, this whole workout can be tweaked for any level of fitness.  you can increase or decrease number of sprints, keep your inclines lower or higher for those treadmills that go higher than 10.0% grade, etc.  you can also adjust this work out to how much time you have to complete it.  if you have more time spread it out and if you're in a hurry, lower the amount of sprints/walks but definitely make sure you warm and cool down!