What about cycling or swimming, instead?

I've heard too many stories of people screwing up their knees by road running. I think someone on this forum even mentioned suffering from it.

Skipping helps with co-ordination and footwork, so that might be better. But 30 minutes of it?

Cycling, obviously, does not work the upper body, so you'd only be doing it to increase stamina / fitness.

It depends what you are trying to get out of this 30 minutes of exercise.

I would combine a number of cardio-vascular exercises, myself. Like I said, 30 minutes of skipping seems a little excessive! Maybe 5 x 3minute rounds, followed by something else to keep your hear-rate up.

Swimming can do so much for you. Think about treading water for 10minute rounds (using only legs, only arms, then both).

What about going into the deep-end so that you are emerged up to your neck, then throwing combinations? Or 100 jabs, 100 crosses, 100 hooks (each hand), 100 uppercuts (each hand), using the water's resistance to your benefit.

You can also easily swim lengths and get your heart-rate up for 20minutes, to help with cardio-vascular fitness.

What about swimming underwater for a length, surfacing, then doing it again?

Just some ideas gleaned from Combat magazine.