It's no secret.  The more muscle you have on your body, the more calories you burn at rest.  Please understand, this does not mean the "leaner" you are, the more calories you burn at rest.  Unfortunately the term "leaner" is widely used to describe a slender body type often lacking muscular definition.  If that's the bodytype you prefer to point your focus toward, then by all means focus on your goal.  If burning fat is your focus, here are a few pieces of information that should help.  1) Getting strong does not require you to feel "dead" after every session. 2) You must eat to get strong 3) Long bouts of cardio can delay strength gains.

1) Getting strong does not require you to feel "dead" after every session.

One more thing that is not a big secret...There is a big movement of fitness professionals moving toward "metabolic conditioning."  Metabolic conditioning is an excellent tool in an arsenal of training methods and often requires maximum output throughout the workout, however most professionals will tell you if you want to get strong, find a strength program and stick with it.  You can sprinkle the occasional metcon in your programming, but understand it does not create maximum opportunity for maximum strength gains. You don't have to feel like you "just died" to get in a beneficial workout.  Find a strength program and follow it.

2) You must eat to get strong

It's true.  Food is a necessity in building strength.  If you break your muscle down you must replenish the nutrients to rebuild it.  Not that this needs to be stated, but we are talking nutritionally dense food.  Find a nutrition program that allows you to rebuild with high quality calorie content.  Just to make the point clear;  Food must be high in nutritional value with protein, yes, some good carbs, and good fats.

3) Long bouts of cardio can delay strength gains.

Cardiovascular activity is never a bad thing, but an excessive amount of cardio can hender your strength program.  To keep this simple and to the point, when your body does cardiovascular activity for a long time, it requires your body to break down muscle tissue for energy.  When doing your cardio within your strength program,  keep your cardio session around 20 minutes.  This will allow your body to burn calories through cardiovascular activity, but will prevent the excessive breakdown of muscle tissue.

If your goal is to burn fat by increasing muscle tissue, take a look into a strength program, assess  your nutrition and don't overdue the cardio.

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