I think of cardio i think of aerobics, running, all that stuff. I am about gaining weight, all cardio seems to do is help lose fat, i dont want to lose any more weight but i do want to work out the heart...so what can i do?

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Dude, just look up High Intensity Interval Training.

Its a type of cardio where you only have to put in 16 minutes a day I think four days out of the week and you're good to go.

No long ass numbing hours on an exercise bike or marathon running races needed.

HIIT takes good conditioning to do though and for a guy in average shape it will probably take you a month or so to work up to doing the 16 minute cycle of it.

Basically it consists of doing moderate paced exercise for a minute and a half and then the next minute and a half or whatever you go as fast and hard as you can with the running or cycling and then basically repeat the cycle until you reach 16 minutes.

Check out the online sites about it for the exact correct instructions on how to do it properly.

I think they don't recommend more than a four minute cycle for a beginner.

It's not necessary to do 1.5 min and then 1 min, there are several intervals you can do: 15 high, 45 low, 8 high, 12 low, and so on

Doing some boxing incorporating HIIT is great, it's fun, raises heart rate quick, and you don't have to do it that often.

If you are about working out the heart and reducing weight lost, crank up the carbs before a cardio workout. This means it'll take longer for the body to burn up the glycogen as a fuel, which equals body taking longer to burn fat, protein etc... All the meanwhile you're still getting a fantastic workout for your heart.