There has been an ongoing debate regarding free weights vs. machines for strength training. While each can help you build strength there are definite pros and cons for each. The following can help you determine what form of strength equipment is best for your needs.
The most important component in any strength training program is safety. If you are new to strength training or if you are working out alone, variable resistance machines are the best bet. While machines can be a viable option for serious weight training, they are best for novice, senior and recreational athletes.
For rehabilitating injured athletes, variable resistance machines are preferred. They provide a more controlled motion and specifically isolate certain muscle groups. Machines also allow you to track progress and provide objective feedback while increasing the protective participation of the healthy limb or muscle group.
Research has shown us that free weights promote quicker strength gains and they require more balance and coordination than do the weight machines. Free weights recruit more muscle groups and more muscle fibers than variable resistance machines, which tend to only isolate specific muscles.
Free weights are also more versatile than machines because they allow for more variations in range of motion. Free weights require balance, and they tend to promote more activity of the joint stabilizer muscles. Finally, they are considerably less expensive than most of the machines on the market. You can perform a complete strength training routine with a few dumbbells, and a little imagination.However, free weights require the help of a spotter, and result in more injuries than machines. Careful instruction and training is necessary to master the art of free weight lifting.
Actually, an ideal training program may incorporate both free weights and machines on alternating training days. In order to get the most from both muscle strength gains and joint stability, you can focus on free weights for some exercises and machines for others.
The bottom line is that you should use the strength training equipment that suits your training needs, is safe, and is convenient. However, if you are comfortable using free weights you may see greater strength gains here than with machines.
Spennewyn KC. Strength outcomes in fixed versus free-form resistance equipment. Journal of Strength and Conditioning Research. 2008;22:75. [http://journals.lww.com/nsca-jscr/Abstract/2008/01000/Strength_Outcomes_in_Fixed_Versus_Free_Form.12.aspx]