I get guys in the gym asking me the same question over and over. They always want to know what is the best workout routine to isolate a particular muscle group. Now that could be their biceps, triceps or abs you name it these guys want to isolate it. Now that gives me the impression that they are missing out on the big picture about strength training. Let me explain why this seems such an odd question to ask.
I want to point out in this article that the body will only work at its peak when all the muscle groups are involved. That is when you perform a single movement, the muscles you are working are not performing in isolation- there are muscle groups in the neighbourhood which are involved and they are vital for you to perform that movement. The bigger guys help the smaller guys, if you like, in performing a complex movement. So, a much better strategy is to try to perform multi-joint complex movements rather that a single-joint exercise.
So, let us say you want to perform a single-joint exercise and you are trying to isolate some muscles. If you do that, you are not allowing the body to perform efficiently and it will be much more likely to suffer from injury. Basically you are building a collection of body parts and not thinking of the whole body as a powerful, wonderfully complex unit working together.
Take a look at some well known athletes Maurice Green and Terrell Owens spring to mind. I can tell you for sure that their coaches would never allow them to do isolation muscle training !And the results you can see for yourself these guys are totally ripped so the answer must be somewhere else. If you continue with isolation training then your chances of getting an injury are much higher and you are likely to end up with a few bandaged joints, tendonitis or even an extra few pounds around your gut. Your body should be working like a powerful machine where all the parts are working together in a functional way and you should have a leaner body capable of performing complex movements or even a simple every day task. If you can concentrate on that, then you will have the extra benefit of a harder leaner body. So focus on how well your body functions overall and forget the isolation myth.
It should be fairly obvious that if you are doing isolation training and concentrating on single- joint movements, the whole body is not involved and therefore your metabolism is not at its full peak. Now think of the complex movement situation and here the metabolism rate will be higher, more calories will be burned and also that means that you are going to produce testosterone and growth hormone which is what you are aiming for really. That in turn means you can lose body fat more easily.
Lets look at an example. The machine leg extension is a single joint exercise that works mainly the quadriceps, can potentially cause knee joint instability in the long run, and doesnt even burn that many calories. On the other hand, exercises like squats, lunges, step-ups, and deadlifts are all multi-joint complex movements that work hundreds of muscles in the body (including the quadriceps) as a functional unit, create more stable and strong joints in the long run (when done properly), and also burn massive quantities of calories compared to the single-joint exercises.