There's nothing more frustrating than giving something your absolute best effort only to find out that you were doing the wrong thing and consequently will get no results.
Cardio is one of those things for many people.
Walk into any gym around the Dallas any day of the week and you'll see dozens of people on the cardio machines pushing themselves hard, straining, giving it their all.
Bless their hearts, they are working so hard...but they are not burning an ounce of fat..
After a while they will typically either quit or try hiring a Dallas personal trainer...and hopefully their trainer will know enough to direct them to a wiser approach...
Anytime you are pushing your body intensely, carbohydrate is the energy source being used. Not fat. This means that if you are straining yourself working hard on a cardio machine then you are not burning fat, you are burning carbohydrate. (ie you are operating in the anaerobic energy zone rather than the aerobic energy zone).
There is nothing inherently evil about the anaerobic energy zone. In fact, its the energy zone that increases your metabolism,. stimulates anti-aging hormones, builds lean muscle, etc, etc.
However....and this is a big big however...
If you are in the anaerobic energy zone constantly for an extended period of time (more than 1-2 minutes) then you cease to derive the positive benefits mentioned above and instead you begin to elevate your cortisol levels which causes you to accelerate the again process, burn off lean muscle tissue, and exhaust yourself with no actual benefit gained. No fat lost. No muscle gained, No metabolism improvement. Just accelerated aging and extreme fatigue.
Its possible that you might have seen a few ultra lean bodybuilders doing cardio for an hour or two straight...nice and slow. Heck they may have just been walking on the treadmill enjoying a movie in fact. You may have wondered how the heck they can get so lean if they're not even pushing themselves.
Well, the answer lies right there in the question itself...
Its the not pushing themselves that is the key. In order to burn fat during cardio you absolutely must keep your heart rate at a level that is low enough that your body is not induced to enter into the anaerobic energy zone in which carbohydrate becomes the primary energy source instead of fat.
We want to burn fat right?
Good, then let's burn fat...not carbohydrates.
There is plenty of need for anaerobic exercise done in a burst type of fashion...but that's not cardio.
to get lean and muscular you need to do
Don't get the two of these backwards.
Many people do. they take it easy when they're lifting weight and then they push hard when they're doing cardio. I couldn't come up with a better recipe for staying chubby if you asked me to.
If chubby is the goal, follow that plan.
If not, follow steps 1 and 2 above.