It is a common misconception that aerobic exercise tones and firms muscles. Actually, it
accomplishes very little toning and firming. Resistance exercise (weight training) is where real toning and firming of muscles occurs.
Doing both aerobics and weight training is the optimal way to lose more fat and gain more muscle. If you are trying to lose weight, studies show that weight loss increases by 56 percent with aerobic and strength exercises combined.
The muscle may weigh more, but when you increase your muscle composition, the body is able to burn more fat, even when you are resting, because your metabolism is higher. A pound of muscle will use 350 to 500 calories per week to survive, while a pound of fat only needs about 14 calories per week. New studies have shown that building muscle helps your body fight disease better, too.