Machines versus Free Weights
There is some controversy over whether it is best to use free weights or machines for your workouts. In general free weights are considered best to build muscle and here's why:
Free weights give you a greater range of motion than a machine does. In addition, with free weights you must balance the weight yourself. Machines help to balance the weight for you. What this means is that when you use free weights you will get a better workout because you will have to use more of your muscles to balance the weight. You will also use more muscle groups in performing each exercise if you use free weights. Because machines are doing some of the work, you don't get as much of a workout when using them.
Why I Still Like Weight Machines
Despite everything I just said above, I still like to use machines for several reasons. The first reason is that in general machines are safer than free weights. If you are using free weights you can't work out alone for a lot of exercises. For example, if you are performing bench presses or squats with free weights you are going to need someone there to spot you. However, if you are using a weight machine to perform your bench presses then you can do these alone because the weight stack on the machine isn't going to fall on you and the bar on the machine only goes down so far so that you can't drop the bar onto yourself.
Another reason that I like to use weight machines is because there are some exercises that are very difficult, if not impossible, to perform well using free weights. Sure, it is possible to exercise your back muscles using free weights, but it just seems so much easier to do lat pulldowns and to use a rowing machine than it is to use free weights.
It is also difficult to exercise your hamstrings using only free weights. But it is easy to do leg curls for your hamstrings on a machine. I've seen weight training videos and books that suggest putting a small dumbbell between your feet to exercise your hamstrings. I've tried it and I found it very difficult to keep the weight in place. Also, there is only so much weight that you'll be able to hold between your feet. If you perform hamstring curls on a machine you can continue to increase the amount of weight you are using in a way that you can't do when using free weights.
It is also possible to use ankle weights to do hamstring curls, but once again, you really can't increase the amount of weight you are using for the exercise like you can when using a machine. However, using ankle weights to perform hamstring curls without a machine is still easier than trying to hold a dumbbell between your feet.
The best way to workout is to use free weights for some exercises and exercise machines for others. In this way you can get the benefits of using free weights for exercises that are safely performed with free weights if you don't have a spotter. You can also use machines for those exercises that are more easily performed using a machine, such as lat pulldowns and hamstring curls.
However, if you don't have access to exercise machines, you can still build a lot of muscle using only free weights. You can also build a lot of muscle if you only use machines. However, you'll see the greatest strength and muscle gains by combining the use of machines and free weights into your workout.