You can get a great cardio workout with the right kind of box jumping routines. Find a 12 inch plyometric stool or “box,” and repeatedly jump onto it, both feet at the same time, and step off, no pausing in between.
Stick it out for one minute (if you can), then take your heart rate; it will be quite elevated and you will be breathing heavily. If you are not breathing hard, you did not move quickly enough. Though box jumping can be done as a strength training exercise, this does not mean that it cannot count as cardio.
This mode of exercise does not have to be done as fast as possible. Pause a few seconds in between each jump, either on the floor or on the platform. The jumping and landing points can also be distanced from shorter platforms. Standard plyometric boxes and stools start at six inches in height and go up in increments of six inches.
Jump nonstop on a 12 inch box at a pace that feels natural, not rushed, and see how long you can do this.
One factor that can force a person to quit before their cardiovascular energy runs out is the quadriceps (thigh) muscle fatigue or burning. The deeper the landing, the more fatigued the quads will get.
It is strongly recommended to not land with a straight-leg as this can damage knee joints. The landing should always come with at least a little knee bend.
Do not think that just because you get taxed within 20 seconds that this is not a cardio exercise. It most certainly is.
If 20 seconds (or 10, 45 or two minutes, etc.) are all you can do, then pace or walk in place for a few minutes to recover, or even step up and down on the platform to recover, then repeat the working segment. This is interval training and is a very effective form of cardio exercise.Resource: OnFitness Magazine