When it comes to building muscle mass and gaining weight, free-weights are by a long shot much more effective than machines in almost all cases.

Why? The main reason is because free-weights require complete strength and coordination of the weight, so your muscles are forced to work harder. If your muscles are working harder, then typically this results in more growth. If the motion of the exercise is supported and guided through its path, such as with machines, then your muscles have much less stress when lifting the weight.

When you workout with free-weights, your muscles are forced to balance the weight through the range of motion without any assistance. This explains why even with what you would consider light weight you may initially find a new type of exercise challenging. The more freedom of motion forces you to use all of your muscles available, whereas most machines eliminate the use of certain muscles, and this obviously will take away from your overall strength and muscle mass.

This is not to say that machines are altogether useless for gaining muscle mass. Many machines do in fact allow you to work out in different angles that free-weights cannot, so in many cases they do have their purpose. However, if you are like most people and want to build muscle mass as fast and efficiently as possible, I'll get right to the point:

STICK TO FREE-WEIGHTS!

Gaining strength in barbell and dumbbell exercises, especially compound exercises such as squats, deadlifts, bench presses, bent-over rows, shoulder presses and a few others will always build much more solid, hard, muscle mass then machines, period. A muscle mass building workout MUST contain mostly free-weights.

If you have been working out on more machines then free-weights and you haven't built a lot of muscle mass lately, this simply switch will work wonders for you. I would personally recommend that to those who are looking for the best muscle mass workout program for fast results eliminate machine exercises completely.

In a nutshell, machines are good for pumping and isolation exercises, and free-weights are for gaining muscle weight fast and packing on serious pounds of muscle in record time. If you are a true hardgainer and have a really hard time gaining weight and building muscle mass fast, then it is absolutely vital that you stick with mainly free-weights, most of the major compound exercises, eat plenty of clean food emphasizing on protein and carbs, get plenty of rest, keep your workouts short and simple, and to be careful not to overtrain.

With these key factors in mind, you should have no trouble gaining weight and building muscle mass as as fast as naturally possible.