The gym can be a fun and inspiring place to exercise, no matter how old or young you are. There you'll find all the equipment necessary for strength and resistance training. This form of physical activity uses weight machines, free weights and resistance bands or tubing to strengthen muscles, bones, lungs and the heart. Resistance training has the ability to improve muscle strength, physical functioning and pain in 50 to 75 percent of people suffering from osteoarthritis of the knee [source: Harvard Medical School].
There are two types of strengthening exercises: isometric and isotonic. Isometric exercise involves contracting the muscle without moving the joint, and it's particularly helpful if a certain joint lacks the ability to move. Isotonic exercise fortifies the muscle by moving the joint [source: MedicineNet].