If you’re new to weight training, you might want to start off using machines because they restrict the range of motion for the specific exercise being performed. Unlike with free weights – which call upon the use of tiny stabilizer muscles that make you use your balance to stabilize the weights – making it easier to use bad form, which can lead to injury. Weight machines isolate the muscle group you’re exercising and position you correctly, forcing you to use good form, greatly reducing the risk of injury. With machines you can use greater resistance because you’re not recruiting the use of the smaller stabilizer muscles needed for balancing free weights; this will allow you to make greater gains in strength faster.

Starting out on machines will give you an idea of the motion for a specific exercise so that when you’re ready to start introducing free weighs into your workouts you’ll have a good idea of how the movements should be done. Remember, weight machines only move one way: the correct way.
 Machines, however, aren’t without their disadvantages. Machines don’t employ the use of the many stabilizer muscles found throughout the body. These stabilizer muscles are important for balance and core strength. The core muscles are the muscles of your abdominals and back that support your spine and keep your body stable and balanced. These core muscles assist the larger muscles in every day activities such as standing, sitting, climbing stairs and walking, and help to protect the back from potential injuries.

Unlike with weight machines, free weights offer you many more options for performing a particular exercise. You can adjust yourself during the exercise allowing you to perform it with better results.

Using free weights allows you to be able to control the plane of movement. Being able to control the plane of movement allows you to target the muscle from different angles which allows you to develop better muscle tone.

Free weight have their disadvantages also, for example; those who are new to weight training might not know how to perform a particular exercise using the correct form, whcih can produce bad lifting habits and increase the chance for injury.

Weight machines, by isolating a specific muscle group, require less energy to perform an exercise. Free weights on the other hand use several muscle groups and in turn require more energy to perform which can help burn fat.

Because both weight machines and free weights have their advantages, your best option is to mix it up between the two. Just remember to use good form when lifting.