Strength training is the process of exercising with progressively heavier resistance to make your muscles stronger. Physiological adaptations occur with strength training. These have a significant impact on your physical appearance for several reasons:

• Human muscle is very active tissue. It has high energy requirements for maintenance and rebuilding.
• Even while we are sleeping, our skeletal muscles are responsible for over 25 percent of our calorie use!
• An increase in lean muscle tissue causes an equivalent increase in your metabolism. That means that your body burns more calories all day long, even while you sleep!
• The converse is true. As many adults lose muscle tissue from lack of exercise, their metabolism slows down. This constant decrease of the metabolism is very closely linked to the steady increase in body fat that often accompanies the aging process.