Our body is a wondrous mechanism and when subjected to unusual stress over a period of time, it adapts itself to deal more effectively with that stress. Therefore, when you exert your muscles against resistance, they are forced to adapt and deal with this extraordinary work load. This is the principle of weight training. Strands of muscle fibers become thicker and stronger in response to the demands placed on them.
One of the great merits of weight training is the strength of your heart. During weight training, your heart is forced to beat faster and stronger in order to pump sufficient blood to the muscles being worked. In time, your heart, like your body, will adapt to this extra-workload by becoming stronger and more efficient. Since your body needs a given amount of blood to perform its daily tasks your heart will now need fewer beats to pump the same quantity of blood. Sounds good? There's more. Your entire circulatory system is given a thorough workout every time you exercise, which increases its overall efficiency. Even the neural paths from your brain's command centers to each individual muscle become more effective, enabling easier recruitment of muscle fibers for carrying out physical tasks. In essence, your body becomes a well-oiled and finely-tuned piece of machinery, whirring along without any breakdown. In today's stress filled world, you need all help you can get.
