What is ''empty stomach'' cardio?

[Milburn]

Cardio exercise must be at morning time before the breakfast.
You can do various cardio exercises with the empty stomach such as morning walk, running, jogging, push ups, pull ups, and sits ups.
To do hard cardio exercises such as swimming you should take some fruits juices and protein shakes.

Maitland Personal Trainer

[Rodja]

Cardio exercise must be at morning time before the breakfast.
You can do various cardio exercises with the empty stomach such as morning walk, running, jogging, push ups, pull ups, and sits ups.
To do hard cardio exercises such as swimming you should take some fruits juices and protein shakes.

All of this information is crap.