Free weights or machines?

Personal trainer Matt Hart replies: Not necessarily so. The secret to effective muscle building has more to do with the training system you employ rather than the specific exercises, which means you can get pretty chunky if you use resistance machines effectively. If you're a beginner, you're probably best starting on the resistance machines to develop some underlying strength and technique. The good thing about the machines is that most of them are designed to keep you in the correct position and some have special camshafts to optimise the loading on the muscle. This means that you can easily isolate a set of muscles and work them thoroughly without having to worry too much about poor form.
As your strength and knowledge of the gym progresses you can start to introduce some free weight exercises, but make sure you book some time with an instructor to run through technique. Poor form with free weights can cause injury and is unlikely to give you the benefits you're after. Once you know what you're doing you'll profit from their versatility and then you can really pick and choose which specific areas of the body you want to work.
Using free weights also makes it easier to develop an even balance of strength throughout the body because they work the limbs independently, although some of machines allow this too. Most serious body builders use a combination of free weights and machines to achieve optimum muscle gain because both types of equipment provide a different array of benefits.