What is alternating high-intensity cardio work with moderate-intensity recovery periods called?

Answer 1

For example, if you were a runner. You would start out running 10 minutes at a moderate, comfortable speed. Next you would take off at a hard sprint for 5 minutes. After the 5 minutes to recover you would decrease your intensity to a moderate level to help your body recover.

Then you would start all over again.

It really helps to tone, build muscle and lose weight.

Answer 2

http://www.aquacert.org/cec22006.pdf

....all the best.