Seek balance when weight training. Work all of your major muscles, including your abdominals, legs, chest, back, shoulders and arms. But strengthen opposing muscles in a balanced way, such as the front of the shoulder and the back of the shoulder. Avoid exercising the same muscles two days in a row. You might work all of your major muscle groups at a single session two or three times a week, or plan daily sessions for specific muscle groups. For example, on Monday work your arms and shoulders, on Tuesday work your legs, and so on.
Want to improve your core strength? Check out this slide show of exercises you can do with a fitness ball.
Starting a weight training program? See how to strengthen your body's major muscle groups.
Learn more about isometric exercises that contract a particular muscle or group of muscles.