Strength training — also known as weight or resistance training — is physical activity designed to improve muscular fitness by exercising a specific muscle or muscle group against external resistance, including free-weights, weight machines, or your own body weight.
Strength training goes a long way in terms of supporting bone health, making aerobic exercise more productive, preventing injury, and facilitating healthy aging.
Isometric resistance involves contracting your muscles against a nonmoving object, such as against the floor in a push-up.
Isotonic strength training involves contracting your muscles through a range of motion as in weight lifting.