If you are a hardgainer, or you just haven't been gaining the muscle mass that you are striving to achieve, you may be leaving out some key exercises. If you look at any successful bodybuilder or weight trainer who trains to build a mass of muscle, you may notice that they spend a lot of time and effort in two main areas of their workouts: leg and back exercises. There are many reasons for this but one of the most particular is because they are the largest and most powerful muscles in your body. Exercises for your legs and back, such as squats, bent-over rows, and deadlifts, are hands down some of the most demanding types of exercises you can do when you train them hard and heavy. But when developed properly they can build a mass of muscle bulk and help you gain weight for the rest of your whole body. Lower body exercises are by far the fasted way to build muscle even if you are trying to increase the muscle mass on your upper body as well. The reason for this is because you are stimulating your largest muscle groups, thus producing the most amount of testosterone throughout your body. Testosterone is a key ingredient you need for workouts for muscle mass development. More testosterone means much more muscle mass potential for the rest of your muscle groups, such as your chest, arms and shoulders. Specializing on back exercises can increase your strength and power and add pounds of muscle on your body in a very short amount of time. Specializing on leg exercises is the fasted way possible to gain weight in the form of muscle mass. A workout designed to specialize on leg and back exercises can add more size and slabs of muscle on your body then a meat factory can produce. You can turn a skeleton into Hercules by just spending a couple months really grinding away ruthlessly on leg and back exercises. They key, however, is to develop strength in just a few of these compound exercises and to work your guts out. Constantly adding weight on a weekly basis is not an option, it's required. Unlike training your arms or smaller muscles, your legs and back can withstand a lot of weight and a lot of endurance. You really have to work them to their maximum, and most trainees never have and never will. That is why most trainees, especially hardgainers, will never get great results. But you are not like most trainees. You are a hard working, determined individual who will do whatever it takes to gain as much muscle mass as possible in the least amount of time (just nod your head and agree on that one). Here are the major leg and back exercises you should focus on if you want to build a mass of muscle on your whole frame really fast: squats, regular deadlifts, stiff-legged deadlifts, bent-over rows, t-bar rows, and dumbbell rows. Note: all of these exercises must be free-weights. NO MACHINES! The goal is strength and power, and nothing can replace free-weights for this. Being a hardgainer myself, I never gained a pound of muscle in 8 long years until I learned about the importance of squats. As soon as I added heavy squats to my workouts for muscle mass I started progressing every week and my weight gains shot way up. Then when I started really focusing on building strength and power in my back exercises as well, my whole frame added much more size and raw power then I have ever seen before. If you are already in the middle of a workout program and have some leg and back exercises incorporated and your goal is to bulk up and gain some quality muscle mass fast, then really focus on those two muscle groups the most. Place them first in your workouts so you can put the most effort and energy into them. The return from hard work on these exercises is better then any other muscle group when you want to build a mass of muscle, raw size, and strength.