The differences between free weights and machines
Exercise, according to the most basic definition, means physical activity that develops or maintains fitness. It also implies being able to control your body, with or without external resistance, while doing the physical exercise.
In free weights, the resistance placed upon your body comes from a freely moving external object such as that found in barbells, dumbbells, kettlebells, and your body mass. These devices, augmented with different sized and weighted throwing objects such as medicine balls and externally loaded vests along with weights attached to the limbs make up the majority of equipment used in free weight training.
In free weight lifting, the challenge is to control and move the load with the correct technique while at the same time stabilizing it and yourself as you complete the movement. These three challenges to your body are not possible when using machines.
When lifting with machines the external load moves in a guided and often times restricted manner. Machines come in all sorts of variations from plate loaded, selectorized, electronically controlled, hidden springs, and rubber band outfits.
None of the currently available machines provides the challenges of free weights. Moreover, the challenges that they do provide will be less than free weights when it comes to the control, stabilization and the movement direction of the load. In fact, it is going to be a rare occurrence when you find a machine that actually fits your body because none of us are built the same.
The bottom line is this: if you want to get stronger and more coordinated, use free weights the majority of your time in the gym, otherwise, you are losing out when it comes to the subtleties of controlling and stabilizing your body while under a load or in living your daily life to the utmost.