Variety is important to weight training because muscles are forced to adapt to changes. Simple tweaks are all it takes to keep your muscles guessing. There are many easy ways to mix things up in the weight room. One way is to add more weight and decrease the number of sets. {relatedarticles}Try that, or try decreasing weight while increasing number of sets. Another way is to try decreasing the amount of time between sets to make your workout a bit harder. Or you can try to superset your exercise -- perform one exercise after another with little or no break in between. If you normally lift dumbbells, then try a resistance training machine for a change. Like machines? Give good old iron-pumping a try, or work in some old-fashioned calisthenics.