One of the debates that continues to rage-on in gyms around the globe is whether free weights or machines are more effective at building muscle. The strange thing is, the only people still debating this are those who are relatively new to lifting weights. Those who have lifted weights for years know through experience which is better.
Ill go ahead and kill the suspense here: free weights are better for building muscle than machines (if you didnt already know). The primary reason is that they force your body to work against resistance in a three-dimensional environment. Machines are typically one-dimensional or two-dimensional at best. This also makes the strength gained from free weight exercises more transferable to daily activities, since nearly everything you do requires strength in all three dimensions.
Not only that, but free weights are also better for the long-term health of your joints. Because they dont keep you locked-in to a set movement pattern you can move as your body is intended to move. This reduces the wear-and-tear on the joints.
But there are advantages to machines. Machines only make your muscles work in one or two dimensions, which decreases the activation of your stabilizer muscles. While this is typically thought of as a negative, this property of machines can actually be used to help us build more muscle.
I find that the stabilizer muscles are often the first to fatigue in a free weight movement. By incorporating machine exercises we take the fatigued stabilizers out of the movement and put all of the stress directly on the muscles we want to target.
With that said, I firmly believe that machine exercises should play a much smaller role than free weight exercises in any fast muscle building program. This is particularly true for beginning and intermediate lifters.
I often see skinny guys in the gym load up a bench press machine with 4 plates per side for a tough set. Yet they cant even do 2 plates on a free weight bench press. But if you ever see someone free weight bench press 4 plates per side (405 pounds) I can guarantee you that they are a large human-being.
This simple real-world example illustrates why the focus of your training should be free weight exercises. But keep in mind that simply throwing a bunch of free weight exercises together and calling it a fast muscle building program wont bring you consistent results. There are a lot of variables to consider when designing a training program, and exercise selection is only one of them.