Weight training is a type of resistance training whereby the body's muscles are used against the force of gravity on weighted discs. The muscles are strongly contracted trying to lift the weights to exercise them and break them down so that they can be built back up even stronger. Very specific muscles can be targeted for use with weights to make them larger, better shaped, and generally more aesthetically pleasing. But weight training can also be a larger part of general fitness. Lifting weights increases heart rate and blood flow, thus working the cardiovascular and circulatory systems. Also, since weightlifting targets specific muscles, you can use it to work muscle areas that don't get much use during everyday activities. Or, you can also use it to help rehabilitate muscles damaged in an accident or medical procedure.