There is one simple reason that you should be using free weights instead of machines. You can build a lot more strength and muscle size from using weights, rather than relying on the machines
There are so many muscle and strength advantages that free weights bring. This means that if you are serious about building massive size and strength then you need to be using weights such as dumbells and barbells.
If you know anything about the great strength athletes and bodybuilders of the past you will know that their core strength program was based around the use of free weights.
Some of the advantages of dumbells and barbells over machines include how research has shown that these weights support faster strength gains. Research also showed that they require more muscular balance and coordination from other muscle groups, than weight machines.
What's more, dumbells also recruit more muscle groups than variable resistance machines. Machines only isolate specific muscles which does not build as much strength or size as machines are designed along a certain range of motion only.
Free weights are also more versatile than weights machines because they give you more variations in the range of motion. For example, when performing a bicep curl with a heavy weight you only exercise the bicep muscle with the machine, whereas you activate more muscles with the free weights.
Another advantage of weights is that in certain circumstances you might want to cheat the curl a little and use a heavier weight. You could not do this with a machine.
Dumbells and Barbells also require balance whereas machines need no balance at all. Dumbells also promote more activity of the joint stabilizer muscles. Most machines do not bring your stabilizer muscles into action, which means you will stay weak in certain movements which is bad and can lead to injury.
The final advantage of free weights is that they are less expensive than most of the machines that you can buy. The great thing with free weights is that you can train from home with just a heavy barbell and two dumbbells. This is all you really need in order to have a great workout.