Here's a challenging (tough, horrible, god-forsaken) cardio routine. It's meant for experienced exercisers who are bored (and crazy). If you're a beginner, you might want to take it down a notch or two. If you try this and it actually kills you, I'm not responsible. Use good judgment; consult your doctor, blah, blah, blah...

All of the machines are interchangeable. You can substitute whatever you have available, or do some machines more than once. The basic premise though, is to do one moderate 10 minute session, followed by seven 3 minute intense intervals. That's 31 minutes of fun and excitement!

The intensity is based on perceived exertion. At a level 5-6, you're in a low training range, you're breathing heavily. You could still carry on a halting conversation, but you couldn't sing the national anthem or anything. This is a level of intensity that you could maintain for an hour or more if you had to.

Level 10 is all out, anaerobic, fast as you can go. This is the level of intensity you would use if someone were, say, chasing you with a butcher knife. There's no way you can keep this up for more than 30-60 seconds without throwing up a lung. In fact, don't feel bad if you can't do a full 1 minute sprint at first. Just go as long as you can stand it.

So, without further ado

Cardio Hell

10 minutes Step Mill, level 6

1 minute EFX elliptical, level 5

1 minute EFX elliptical, level 10

1 minute EFX elliptical, level 5

1 minute treadmill, level 5

1 minute treadmill, level 10

1 minute treadmill, level 5

1 minute Lifecycle, level 5

1 minute Lifecycle, level 10

1 minute Lifecycle, level 5

1 minute Stairmaster, level 5

1 minute Stairmaster, level 10

1 minute Stairmaster, level 5

1 minute rowing machine, level 5

1 minute rowing machine, level 10

1 minute rowing machine, level 5

1 minute BodyTrek elliptical, level 5

1 minute BodyTrek elliptical, level 10

1 minute BodyTrek elliptical, level 5

1 minute jump rope, level 5

1 minute jump rope, level 10

1 minute jump rope, level 5

How do you change the intensity on a jump rope, you ask? You double bounce at a normal rate for level 5, then single bounce and turn the rope faster for a level 10.

I highly recommend at least a 5 minute walk on the treadmill to cool down when you're done.