Training movements through compound exercises, single limb and alternating limb exercises will bring about the greatest real world performance improvement... Not training muscles through Isolation exercises.

For performance improvement you can actually use in the real world, you must train movements that are multi-planar and multi-jointed.

People in movement almost never isolate muscles or joints... so why train that way?

Favor compound exercises over Bodybuilder type isolation exercises.

Remember, Bodybuilding programs are specifically designed for muscle growth, not muscle performance... and are definitely not for training the body to work as one complete unit.

Compound exercises use multiple muscle groups in unison to perform the movement... much like we move in sport, work and life activities.

Let's take a look at the worst possible combination... isolation exercises on machines.

First of all I would like to say that I am not completely against the use of machines under certain circumstances.

For example, I believe that the use of machines for physical therapy and rehabilitation can be very helpful.

If one isolated muscle needed to be rehabilitated due to injury, using a machine that isolated that muscle would be a very productive, safe and controllable way to improve that muscles performance.

The goal of the therapy would be to bring the injured muscle up to the performance level of the rest of the body... allowing it to contribute to compound exercises and multi-planar, multi-jointed movements.

But what happens after the muscle has been rehabilitated and functions equally with the rest of the body... would you continue to isolate it with the hopes of further improving performance?

I think not... you would move on to some other type of training to use the healthy muscle in conjunction with the rest of the body to improve over-all performance... such as compound exercises.

Does this mean that the vast majority of commercial gyms believe your fitness level is so bad that you must use rehabilitation methods?

It is definitely something to think about.

I believe that the reliance of machines in the fitness industry comes from trying to develop a system of physical training that can be used for the greatest cross-section of the population with relative safety... but this does not mean that it is the most effective training method.

Now, just because I have focused on machines does not mean that I am in favor of isolation exercises done with free-weights or any other method.

The reason I do not favor isolation methods is that it leaves gaps in your strength... whereas compound exercises train the body to perform as one complete unit.

Let's say that you train the bicep curl and military press separately... what happens when you have to curl and press an object in one fluid motion?

The transitional period of the movement between the end of the bicep curl and the beginning of the military press would rob the movement of strength since that movement had never been trained.

I am assuming that the purpose of your physical training is to optimize your performance for sport, work and life... and not just improve performance in the controlled environment of the gym.

You will perform how you train... so train the same movement patterns that you actually use in the real world by using compound exercises, single limb and alternating limb movements.

Compound exercises, single limb and alternating limb exercises most closely mirror how we perform in nature... so it would stand to reason that the greatest amount of usable, real world performance improvement would be made by training these exercises.

I would further contend that the majority of activities in the real world are done with the feet planted firmly on the ground... therefore, for the greatest amount of functional improvement your training should take place in this fashion.

Unless there is some specific reason you need great amounts of isolated strength while seated or lying down... concentrate your physical training on compound exercises, single limb and alternating limb exercises where your feet are in contact with the ground.