If you want to lose weight or gain muscle you have to force your body to adapt to a new stimilus every now and then. If you don't believe just look at the people at your gym that has been doing the same thing for years and you will see they look the same that they did when you first saw them. I attached an article from MSN that explained why you should vary your exercise routine periodically.
Efficiency is a good thing when you're talking about running your business. But it sucks the benefits out of your diet and workout. The more efficient your body is at exercise, the fewer calories it burns. Think of the guy in your health club who does the exact same workout every time you see him, with the exact same weights. He never looks better from one year to the next because his body has become so efficient at doing those moves that it doesn't need to grow bigger muscles or burn more fat in order to finish the workout.
Science has shown us some good strategies for making exercise less efficient:
You can make your lifts less efficient in two ways by increasing the amount of weight you're lifting, or by choosing exercises that are more challenging to your balance and coordination.
Let's say your maximum bench press is 200 pounds. Lifting 200 pounds once is very inefficient; your body throws every muscle fiber into it. But lifting 50 pounds four times is very easy, and thus efficient. The metabolic cost of lifting 200 pounds once is thus greater than the cost of lifting 50 pounds four times. Doing maximum-effort sets of three to six repetitions with, say, 165 to 185 pounds would be a better way to overload your metabolism than doing sets of 10 to 12 reps with lighter weights.
The least efficient lifts are those in which the weight is over your head. This would include standing shoulder presses, as well as exercises such as squats or lunges in which you hold a weight overhead. So instead of doing shoulder presses in a machine or sitting on a bench, stand and crank them out.
No surprises here: If you perform intervals, in which you go hard, then easy, then hard again, you take the efficiency out of your run, swim, or ride. You can call this the "Old Science of Weight Loss," since studies have shown the fat-burning benefits of intervals since the early '90s.
Your diet, too, can be made less efficient, and thus more calorically costly. I showed in the previous section how a higher-protein diet kicks up your metabolism, a sign that your body is burning calories inefficiently. But if that protein comes in the form of high-calcium dairy milk, yogurt, cheese you take the inefficiency one giant step further.