The first thing a novice weight lifter does when he enters the gym is to head for the machines. Why? Because it’s easier. There are pictures on the machine that gives directions on how to use the machine. All you have to do is adjust the knobs and you are ready to go.
Unfortunately, machines are inferior to free weights in terms of strength gains and balance training. Free weights recruit more muscle fibers and the need for proprioception while lifting free weights helps the central nervous system develop balance.
Free weights are also safer than machines if you are properly trained in using them. Free weights are considered more dangerous because you can receive serious injury or even death while doing exercises such as the barbell bench press and barbell squats. If you plan on lifting heavy for these lifts, a spotter is not optional, it’s required. Take the time to research free weight exercises on the internet or at the library. You can always ask a more experienced weight lifter for help, don’t be shy, most people love to help out newbies.
Machines have a higher chance of causing injury because they are designed for the person of average height and limbs. If you do not fall into this range, the machine will work your muscles at angles that can injure your joints. This is especially true for machines such as the leg extension and leg curl. They can place a large amount of shearing force on your knees.
These machines are a poor substitute for barbell squats and should be avoided. That is not to say that machines are completely useless. For the advanced weight lifter, machines can be beneficial in sculpting problem areas and cables in particular are very useful for achieving this result.