That's exactly what I would've said... Anything that gets your heartrate up - usually in the range of 60-80% of max but really there's no need to be that specific. Anything that gets your heart pumping faster than usual, more basically.
So anything from fast walking to jogging to running, to bike riding, to jumping jacks, skipping rope, dancing, using any of the cardio machines at the gym... chasing your kids around the playground... etc.
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Re: What is considered cardio?
Anything that gets your heartrate up - usually in the range of 60-80% of max but really there's no need to be that specific. Anything that gets your heart pumping faster than usual, more basically. 
