HIIT stands for High Intensity Interval Training, but don't let the name intimidate you. We do rounds of cardio, upper body, lower body, and Abs/Core with short rests in between. The idea here is to get the heart rate up, then let it come down, which is called Interval Training. Studies suggest that this is the fastest way to burn calories and in turn burn fat for the slimmer, trimmer, toned YOU! Modifications to almost every exercise are given for those who are less advanced, and/or have limitations due to injuries.
Read about the benefits of Interval Training:http://www.mayoclinic.org/healthy-lifestyle/fitness/in-depth/interval-training/art-20044588?pg=2