The thought process behind HIIT is that through doing a workout more intensely than an average workout you increase the heart rate, lessen the rest between exercises and burn extra calories and fat. When you are done with a HIIT workout you will be hot, sweating and know that you just got a good workout.
HIIT Treadmill Workout
HIIT treadmill workouts are great because you can do them even if you are just beginning to get back into shape or are just beginning to try these types of workouts. Start out with a nice jog and then increase the speed by 1.5-2 miles per hour and try running at the new speed for 45 seconds - one minute. Then go back to the previous jogging speed. Then after 30 seconds increase the speed again for a 2- 2.5 miles per hour increase. Continue doing this for 10-15 minutes or so. The key is to vary the speed to keep your body confused about what is coming next. You should do a warm up and a cool down period with the workout. You can also increase the angle while running to make it even more challenging. Here is an example of a HIIT workout on the treadmill from Trainer Josh .
HIIT At Home Workout
The same type of workout can be done at home. Again the advantage to these exercises is that the time it takes to get a good workout is deminished and the workout is a good way to burn fat and get your heart rate up. When doing exercises at home make sure all furnature or other objects are out of the way so you don't injure yourself or break anything. This would be similar to P90X or Insanity . One guy that does a lot of HIIT routines at home is Mike Chang. Below is a video he did of a sample HIIT workout.
Try these exercises at have and see if you find these more effective at getting a good workout. Please let me know what you think.