I also find kickboxing to be very intense, whether it be high or low impact. Cathe's Cardio Kicks is higher impact because she does a lot of shuffling, jack, slides, skips, jumprope etc. which really help keep that heartrate up there! However, there are not as many kicks in CK as there are in a lot of other kickbox videos I've done. If you go with a kickbox video that has less impact, be sure that you are getting sufficient kicking drills as they use the larger leg muscles and get your heartrate up without a lot of hopping around. For example, I just got the Powerstrike video Millenium II (and I can still feel it in my arms ;-)) and the impact is very low but they keep you using your large muscle groups with punches, kicks and squats.