Boxing is the ultimate cardio training. The interval training is 3 minutes on 1 minute rest.

The Time Clock is a must when you do this exercise. It keeps you honest and prevents you from cutting yourself slack when you get tired. There is a lot going on that demands good technique when training on the heavy bag.

A real professional fighter not an amateur is your best bet when you get instruction. Non fighters and amateurs are quitters they didn't stick to it to long enough or didn't believe that had what it takes. Fighters train like a champion. No quit, Good Focus, and all the other superlatives that go hand in hand with achievement. Here is a video of Jhoon Rhee doing over 100 pushups in a minute. He was 68 years old. Here is his intro.